NSN UMTS Fundamentals
Short Description
UMTS...
Description
UMTS Fundamentals
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Foreword The training materials that are handed out are meant for training purposes only. The accompanying document is not a replacement for the official system documentation, and is not meant for selfstudy. The official system documentation is the only licensed reference work for carrying out work in the field. This student file is your own property. At the end of the course, your course conductor will give you some course evaluation sheets. We ask you to fill out these sheets and would be pleased to receive suggestions for course improvement regarding the carrying out of the courses and material used. We at Nokia Siemens Networks wish you successful training.
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Training Management
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Overview of UMTS Technology and its Evolution
1 57 pages
Course overview
2
UMTS Network Architecture 58 pages
This workbook consists of 7 chapters and 498 pages total.
UMTS Fundamentals
Principles of UMTS Terrestrial Radio Access (UTRA)
3 108 pages
4
UMTS Identity and Traffic Management 80 pages
5
Signaling Protocols Overview zezenenu.und.lmm
84 pages
6
UMTS Services and Applications 33 pages
7
NSN Products 78 pages
Overview of UMTS Technology and its Evolution
Overview of UMTS Technology and its Evolution
Contents zezenenu.und.lmm/tuxonuqu.en.slo
1
Module Objectives.....................................................................................3
2 2.1 2.2 2.3 2.4
Cellular System: Advantages of Digital Technology............................ 4 First Steps & First Generation (1G) ............................................................ 4 Second Generation (2G) Mobile Systems................................................ 10 Third Generation (3G) ............................................................................... 16 Basic UMTS .............................................................................................. 17
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3.3 3.4
3G UMTS Motivation and Specification Process for UMTS ........................................................................................................ 21 UMTS Development..................................................................................21 Mobile Communication Market: Medium and Long Term Forecasts...................................................................................................21 3G end-to-end IP Solutions.......................................................................23 Specification Process for UMTS ............................................................... 25
4 4.1 4.2
Evolution of UMTS Technology.............................................................28 GSM & UMTS Evolution........................................................................... 28 Data Transmission Evolution.................................................................... 30
5 5.1 5.2 5.3 5.4
Existing GSM and UMTS Service Concept........................................... 32 User Services............................................................................................32 GSM Service Support in UMTS ................................................................ 33 WCDMA in UMTS ..................................................................................... 34 Flexible Service Creation.......................................................................... 36
6 6.1
New Evolutions........................................................................................39 IPTV ...........................................................................................................39
3.1 3.2
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Overview of UMTS Technology and its Evolution
WiMAX.......................................................................................................43 Long Term Evolution (LTE).......................................................................48
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Appendix.................................................................................................. 50
8 8.1
Exercises..................................................................................................52 Solutions....................................................................................................55
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6.2 6.3
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Overview of UMTS Technology and its Evolution
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Module Objectives
The aim of this module is to give the student the conceptual knowledge needed for explaining the basics of Universal Mobile Telecommunication System (UMTS). Topics to be covered in this module include visualizing the whole network and identifying the elements of each subsystem. After completing this module, the participant should be able to: Identify the principles of cellular system Identify and list the components in 2G Identify the motivation factors for 3G Identify the specification process Explain GSM and UMTS service concept
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Overview of UMTS Technology and its Evolution
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Cellular System: Advantages of Digital Technology
In the following section, we will discuss the principle of cellular system and the advantages of it moving towards digital technology. There are three different generations as far as mobile communication is concerned as discussed below: 1.
First Generation (1G)
2.
Second Generation (2G)
3.
Third Generation (3G)
First Steps & First Generation (1G)
The first generation, 1G, is the name for the analogue or semi-analogue (analogue radio path, but digital switching) mobile networks established after the mid-1980s, such as Nordic Mobile Telephone (NMT) and Advanced Mobile Phone System (AMPS). These networks offered basic services for the users, and the emphasis was on speech and services related matters. 1G network were mainly national efforts and very often they were specified after the networks were established. Due to this, the 1G network was incompatible with each other. Mobile communication was considered some kind of curiosity, and it added value service on top of the fixed networks in those times.
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2.1
Overview of UMTS Technology and its Evolution
The following figure describes the First Generation Communication System:
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Fig. 1 First Generation Communication System.
The history of mobile communication starts with the transmission of information via High Frequency (HF) in the late 19th century. Even after HF speech transmission became possible in the first decade of the 20th century, it needed further 40 years, before the first mobile networks for private user started operation.
2.1.1
Simplex / Duplex Transmission
Simplex transmission means to be a communication "one-way street". Transmission in only one direction (to or from the mobile user) is possible at a certain time. Simplex transmission is used e.g. for radio and TV transmissions. Simple mobile communication systems use the so-called Semi-Duplex Transmission, i.e. at a certain time it is only possible to transmit data in one direction, but the direction can be changed (used in ancient mobile systems and walkie-talkies). Duplex transmission is used for simultaneous, bi-directional information exchange. Modern telecommunication systems are based on duplex transmission.
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Overview of UMTS Technology and its Evolution
2.1.2
Single Cell Systems
The first mobile networks offering duplex transmission car phone telephone service to private user started operation in the late 1940's in the USA and in Europe during the 1950's. These systems have been created as Single Cell Systems. Single Cell Systems provide service in the service area (cell) of several Base Stations BSs, but every cell is far remote from others to prevent interference between different users (resulting in disruption of the connections). Every single cell was totally independent from the others. This caused the several problems, for example: low system capacity no "Handover" possible no seamless service areas no call toward the mobile user without knowledge of his current location The following problems were also encountered by the first mobile services: poor service and speech quality manual switching (operator needed) heavy, cumbersome, massive, expensive equipment (only for car phone)
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Single Cell Systems have been used until the m1990's, becoming less and less important with the introduction of the cellular systems at the end of the 1970's.
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Overview of UMTS Technology and its Evolution
Cellular system is illustrated in the following figure:
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Fig. 2 Single Cell System
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2.1.3
Principle of Cellular Systems
According to a cellular principle a large number of Base Stations (BS) that provide full service coverage, their cell areas overlap each other significantly. To prevent interference between subscribers using the same frequency, only part of the available frequency range is used in a cell. The same frequency range is only permitted to be used in another cell sufficiently distant from this first cell (re-use distance). The area in which the entire "set of frequencies" is once used is known as the cluster. The number of calls that can be made at the same time in a particular area is no longer determined by the available frequency range but by the size of the available cells. Cellular Systems are the prerequisite for:
Cellular Systems were tested in many countries at the end of the 1970's. In 1979, AMPS started commercial operation in the USA and the Nippon Telegraph & Telephone Company - Mobile Telephone System (NTT-MTS) in Japan. Both systems operated in the 800-MHz range. In the beginning of the 1980's, the NMT system was launched in the 450-MHz range and later in the 900-MHz range in the Scandinavian countries. NMT was the first cellular system allowing International Roaming. In 1985 the Total Access communication System (TACS) was introduced in Great Britain in the 900-MHz range. Some of the European Countries where NMT and TACS Systems were introduced in the 450- MHz range are: Italy: The RTMS system. Germany: The C450 system France: The Radiocom2000 system The introduction of the cellular system principle for mobile communication in the late 1970's made it possible to increase the number of mobile subscriber from less than 1 million world-wide to more than 500 million between 1980 and 2000.
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Roaming Handover Enhanced network capacity
Overview of UMTS Technology and its Evolution
The following figure explains the principle of cellular system:
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Fig. 3 Principle of cellular systems
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Overview of UMTS Technology and its Evolution
2.1.4
Limitations of the 1G
Cellular 1G systems transfer analog information over the radio or air interface. Shortly after introduction of the first "analog" mobile communications systems, it became evident that the exponential growth in subscriber numbers in mobile communications would quickly saturate the capacity. A further problem entailed the frequently poor speech quality and service availability of the "analog" systems.
2.2
Second Generation (2G) Mobile Systems
2.2.1
2G Cellular Systems
Global System for Mobile Communication ( GSM ) In 1990 the GSM Standard was ratified as first 2G standard. Commercial operation of GSM systems started in late 1991. Originally planned as a European system, GSM spread all over the world, serving 2/3 of all mobile subscriber in 2001. The GSM radio interface uses FDD for duplex transmission and FDMA/TDMA for multiple access. GSM systems are existing in the 900, 1800 and 1900 MHz frequency range. Digital Advanced Mobile Phone System ( D-AMPS) D-AMPS (also refered as IS-136 or US-TDMA) was conceived in 1991/1992 in America as an enhancement of the 1G AMPS standard. The D-AMPS radio interface uses FDD for duplex transmission and FDMA/TDMA for multiple access. The 800-MHz band (824-849/869-894 MHz) is used in conjunction with AMPS. D-AMPS was extended in 1995 to the 1900-MHz frequency range. AMPS and D-AMPS serves some 10% of the world-wide mobile subscriber in 2001. Japanese Digital Cellular ( JDC) / Personal Digital Cellular (PDC) PDC, originally titled as JDC is used in Japan only. Commercial operation started in1993/1994. The PDC radio interface uses FDD for duplex transmission and FDMA/TDMA for multiple access. PDC is used at the 900-MHz band (810-826/940-956 MHz) and 1500-MHz band (1429-1441, 1501-1513). In 2001 some 70 million subscriber used PDC in Japan.
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The large numbers of historically evolved, incompatible analog standards in Europe at the end of the 1980's also represented a barrier in a converging European market. As early as the beginning of the 1980's it became clear that a new, uniform cellular system/standard at European level had to be developed. The first system in the so called second mobile communications generation (2G) deriving from this initiative was the GSM Standard. The 2G systems differs from the 1G system in the respect that the 2G systems transmit digital information.
Overview of UMTS Technology and its Evolution
Interim Standard-95 ( IS-95 ) IS-95 CDMA was developed at the beginning of the 1990's on the basis of CDMA technology. Commercial operation started 1995. The IS-95 radio interface uses FDD for duplex transmission, which is different to GSM, D-AMPS, and PDC. CDMA for multiple access frequencies in the 800-MHz and 1900-MHz bands are used globally and also in the 1700-MHz band in Korea. IS-95 CDMA are used all over the world, serving some 100 million subscriber in 2001.
2.2.2
Development of the GSM Standard
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In 1978, the Conférence Européene des Postes et Télecommunication (CEPT) reserved 2 x 25 MHz in the 900-MHz band for a future European mobile communications system. A team of experts – the “Groupe Special Mobile” (GSM) – was set up in 1982 to develop this standard. The objective was to create a binding, international standard for cellular mobile communications systems in Europe. In 1988, the new-founded European Telecommunication Standard Institute (ETSI) took over standardization work and finished work on the standard, which has been re-named to Global System for Mobile communication (GSM). The standardization of GSM900 and GSM1800 is finished in year 1990 and 1991 respectively. Commercial operation started late 1991. In the following 10 years, GSM became the quasi-world standard for mobile communication, serving some 2/3 of all mobile subscriber in 2001 (some 550 million). GSM Adaptations / The GSM family GSM 900 : 890 - 915 for up link and 935 - 960 MHz for down link. effectively 2 x 25 MHz used world-wide. E-GSM: Extended GSM. An additional 2 x 10 MHz can be made available in EGSM on national decision. 880 - 915 MHz / 925 - 960 MHz, 2 x 35 MHz. GSM1800, formerly Digital Cellular System (DCS1800): 1710 - 1785 MHz / 1805 - 1880 MHz, effectively 2 x 25 MHz used world-wide. GSM1900, formerly Public Cellular System (PCS1900): 1850 - 1910 MHz / 1930 - 1990 MHz, effectively 2 x 60 MHz. Developed especially for the American market. GSM Railway (GSM-R): 876 - 880 MHz / 821 - 825 MHz, effectively 2 x 4 MHz. GSM-R is the GSM adaptation for railway systems. GSM450: 450.4-457.6 MHz / 460.4-467.6 MHz, effectively 2 x 7.2 MHz GSM480: 478.8-486 MHz / 488.8-496 MHz, effectively 2 x 7.2 MHz. GSM450 & GSM480 have been defined to re-use 1G frequency ranges by GSM. GSM850: 824-849 MHz / 869-894 MHz, effectively 2 x 25 MHz. GSM850 has been defined to replace North American 1G AMPS systems by GSM.
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Overview of UMTS Technology and its Evolution
2.2.3
GSM Evolutionary Concept
The GSM Standard was originally intended to include all specifications on its ratification. However, in 1998 it became clear that not all planned services and half rate speech could be offered within the specified deadlines. This led to a crucial decision that GSM was not to be declared as a closed, immutable standard, and need to be further developed in phases. This evolutionary concept provides flexibility for modifications and technical innovations and allows GSM to be adapted to market requirements and the latest technical developments. GSM Phase 1 The standardization ratified in 1990 for GSM900 and in 1991 for GSM1800 is referred to as GSM Phase 1. Phase 1 of the implementation of GSM systems includes all central requirements for the transmission of digital information. Speech data transmission is of core importance. Data transmission is likewise defined at rates of 0.3 to 9.6 kbit/s. GSM Phase 1 has only a few Supplementary Services (SS) such as call forwarding and barring. Work on GSM Phase 2 was completed in 1995. In this phase, supplementary services, in particular, with features comparable to ISDN were added to the standard. Technical improvements were also specified such as half-rate speech. An important aspect of Phase 2 was the declaration of downward compatibility – i.e., all Phase 2 networks and terminal equipment must retain compatibility with the Phase 1 networks and terminal equipment. GSM Phase 2+ Phase 2+ indicates ongoing development. The GSM Standard will not be fully revised; instead, individual topics can be separately treated. The Standard has been updated annually since 1996 (Annual Releases '97 – '99). The current topics relate to new supplementary services, services for special user groups, improved voice codecs, IN applications and high data rate services. The milestones in GSM evolution are explained in the following figure:
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GSM Phase 2
Overview of UMTS Technology and its Evolution
Fig. 4 Evolution of GSM zezenenu.und.lmm/tuxonuqu.en.slo
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Overview of UMTS Technology and its Evolution
2.2.4
Advantages of the Digital Transmission
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1.
Network Capacity: Compression of digitized speech information can considerably increase the capacity of mobile communication networks. Speech compression must be weighed against a reduction in speech quality however. Compression in speech from 64 kbit/s (digital fixed network transmission) to 2.4 – 13 kbit/s is used in the different 2G systems for transmission over the air interfaces.
2.
Security Aspects: Unlike analog signals, digital information can be very easily ciphered, preventing unauthorized eavesdropping of user data.
3.
Supplementary Services: Digital data transmission greatly simplifies the transfer of signaling information thereby allowing the introduction of a wide range of supplementary services not confined to just pure speech and data transmission.
4.
Cost Factor : Digital devices are less expensive to produce than analog devices thanks to better options for the use of large-scale integrated microelectronic components. Purchasing costs, as well as operating and maintenance costs, are lower and opened the way for the 2nd generation to the mass market.
5.
Miniaturization: Microelectronics for digital information transmission allows a HW reduction that is relatively simple compared to analog HW elements. In this way, the size and weight of Mobile Stations MS could be reduced very much from 1G to 2G, allowing turning over from car phone to handhelds. The weight of handhelds decreased during the 1990's from more than 500g to less than 100g.
6.
Transmission Quality: During transmission across the air interface the signals experience considerable fading, distortion and corruption. Digital signals can be treated easily with redundancy, can be better regenerated and offer therefore significantly better transmission quality than analog signals. Analog signals can only be amplified (including all disturbances).
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Mobile communication followed the trend set in fixed networks in the mid-1980's under the term Integrated Services Digital Network (ISDN). Following are several advantages that are correlated with the introduction of 2G digital transmission:
Overview of UMTS Technology and its Evolution
The following figure explains the Advantages of the digital transmission:
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Fig. 5 Advantages of Digital data transmission
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Overview of UMTS Technology and its Evolution
2.3
Third Generation (3G)
The third generation, 3G, is expected to complete the globalisation process of the mobile communication. Again there are national interests involved. Also some difficulties can be foreseen. Several 3G solutions were standardised, such as Universal Mobile Telecommunications System (UMTS), cdma2000, and Universal Wireless Communication-136 (UWC).
The system to be developed must be fully specified (like GSM). The specifications generated should be valid world-wide. The system must bring clear added value when comparing to the GSM in all aspects. However, in the beginning phase(s) the system must be backward compatible at least with GSM and ISDN. Multimedia and all of its components must be supported throughout the system. The radio access of the 3G must be generic.
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The 3G system UMTS is mostly be based on GSM technical solutions due to two reasons. Firstly, the GSM as technology dominates the market, and secondly, investments made to GSM should be utilised as much as possible. Based on this, the specification bodies created a vision about how mobile telecommunication will develop within the next decade. Through this vision, some requirements for UMTS were short-listed as follows:
Overview of UMTS Technology and its Evolution
2.4
Basic UMTS
2.4.1
The UMTS PLMN (UMTS Phase 1)
The UMTS PLMN as defined in UMTS Rel. ’99 consists of the following: Core Network functional units from GSM Phases 1/2 (MSC, VLR, HLR, AC, EIR) GPRS functional units (GGSN & SGSN) CAMEL functional units: CSE (gsmSSF & gsmSCF) The radio component, UMTS Terrestrial Radio Access Network (UTRAN).
2.4.1.1
UMTS-specific extensions / modifications
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The Core Network (CN) needs only minor modifications to introduce UMTS. A number of protocols need to be extended, for example, to enable transfer of the new UMTS subscriber profiles. In a similar manner, the corresponding registers have to be extended in order to save the data. Another modification is the relocation of the transcoding TC function (for speech compression) in the CN. The TC function is needed together with an interworking function (IWF) for protocol conversion between the A and Iu interfaces. The main differences between GSM (Phase 2+) and UMTS are due to the new principles of radio transmission (WCDMA instead of FDMA/TDMA). UTRAN, as the radio transmission component of UMTS, is therefore the main modification. UTRAN is connected to the Core Network (CN) via the Iu interface. Circuit-switched data is transferred by UTRAN via the Iu(CS) interface to the MSC/VLR, while packet-switched data is transferred via Iu(PS) to the SGSN.
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Fig. 6 UMTS Phase 1
2.4.1.2 UMTS Terrestrial Radio Access Network (UTRAN) The introduction of the UMTS radio transmission component – UTRAN – is connected with the introduction of new network elements and interfaces. The UTRAN network elements are as follows: Radio Network Controller (RNC). UTRAN is divided into individual areas known as Radio Network Systems (RNS). Each RNS, to which a flexibly definable number of UMTS cells belong, is controlled by a RNC. An RNC is a central unit for switching data in UTRAN and for formatting the data for transport over the UMTS radio interface. An RNC is also solely responsible (independent from the CN) for all radio-based decisions: autonomous Radio Resource Management (RRM). The functionality of an RNC is comparable with that of a GSM BSC. However, its functions are designed for greater autonomy and are adapted for compliance with the new radio interface. Node B. One or more Node B's are controlled and addressed by an RNC. A Node B is a physical unit for implementation of the UMTS radio interface. As a central transmission and reception site, it serves one or more UMTS cells (an omni cell with 360° service or, for example, 2, 3 or 6 sector cells with 180°, 120° and 60° service respectively).
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Overview of UMTS Technology and its Evolution
Overview of UMTS Technology and its Evolution
The UTRAN interfaces are as follows: Uu interface: The Uu interface provides the UMTS radio interface and connects Node B with the UMTS user equipment (UE). Iu interface: The Iu interface connects an RNC with the CN – i.e., with the MSC/VLR and SGSN. Iub interface: Connects an RNC with the Node B's that it controls. Iur interface: Connects different RNC's together. It has no equivalent in GSM and is due to a handover method (known as soft handover) not typical in GSM. Uu, Iu, Iub and Iur are open interfaces – i.e., specified in the UMTS Recommendations. They use different transmission methods from GSM.
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Fig. 7 UMTS Terrestrial Radio Access Network (UTRAN)
2.4.1.3 Overview: The UMTS (Phase 1) PLMN The UMTS PLMN is based on a GSM PLMN extended during UMTS introduction by the Phase 2+ features "GPRS" and "CAMEL". The UMTS-specific modifications to the CN required during the UMTS introductory phase (e.g., TC/IWF between Iu and A interfaces) are minor and therefore reduce the costs and minimize the risks associated with UMTS implementation.
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Overview of UMTS Technology and its Evolution
The introduction of the UTRAN network elements RNC and Node B along with the UMTS user equipment (UE) and the connecting interfaces (Iu, Iur, Iub and Uu) are specific to UMTS. These interfaces use different GSM transmission principles. Uu uses the CDMA method for transmission, the GSM radio interface, Um, uses FDMA/TDMA. Iu, Iur and Iub are based on ATM transmission, while their GSM equivalents (where existing) use TDM (Time Division Multiplexing). The UMTS UE is based on the same principles as the GSM MS's – in other words, separated into ME and UMTS SIM cards (USIM). The UMTS UE, in particular during the UMTS startup phase, may have dual mode functionality (UMTS & GSM) or even multimode functionality (UMTS & GSM & MSS or MC-CDMA,...).
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BSS and UTRAN, both serviced by the same CN, may even possibly co-exist. This will be of great advantage, particularly in the startup phase of UMTS. UMTS can be introduced in financially attractive hot spots and gradually expanded. Nonetheless, with dual mode UE (UMTS & GSM) services can be provided from the very beginning of UMTS operation throughout the widespread service areas of GSM.
Fig. 8 UMTS Phase 1 Summary
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Overview of UMTS Technology and its Evolution
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3G UMTS Motivation and Specification Process for UMTS
3.1
UMTS Development
The European Telecommunication Standard Institute (ETSI) Global Multimedia Mobility (GMM) Report from 1996 pointed the way for the development not only of UMTS, but also of GSM. GSM was to be further evolved in the GSM Phase 2+ in such a manner that its capabilities progressed toward UMTS. The GSM network and protocol structures were developed so that they can be used as a platform not only for high level GSM services, but also for UMTS. UMTS will continue the GSM success story. The existing infrastructure of the GSM operators will be more intensively used, and also for UMTS. This reduces the financial risks involved in the introduction of UMTS. In other words, the 2G investments will continue to be utilized. zezenenu.und.lmm/tuxonuqu.en.slo
The experience gained by GSM with regard to the core network and the Protocols and procedures (for example, the MAP protocol, call control, mobility management, handover, etc.) will also be used either directly or in a modified form. Using these Protocols and procedures will also reduce the risks involved in the 3G implementation. The introduction of dual and multimode terminals is of great importance. It will use the entire area serviced by GSM from the very beginning by handover between UMTS and GSM, thereby paving the way for UMTS (reduction of 3G risks). This new evolutionary plan gives 2G operators a chance to reconfigure their networks for upward compatibility, and UMTS operators can avail of the downward compatibility to assure successful UMTS launching. In this way GSM will slowly evolve along a migration path toward the original objectives of UMTS to obtain the smoothest possible transition from the 2nd to the 3rd generation of mobile communications.
3.2
Mobile Communication Market: Medium and Long Term Forecasts
The mobile communications market will continue to grow in the first decade of the 21st century and beyond. Unlike the fixed network sector, which over the last decades only developed slowly and which is only recently gaining momentum again, many market studies indicate unrestricted expansion of the mobile communications sector even well beyond the year 2010. This growth is only likely to be overtaken by the forecasts for the Internet market.
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Overview of UMTS Technology and its Evolution
It is generally expected that the number of mobile communications subscribers will exceed those in fixed networks in the next years. This is already the case in particular in regions with a poorly developed fixed network infrastructure. About 2.7 billion subscribers are predicted for the mobile communications market by the year 2015 according to the UMTS Forum Report #1. This growth is being experienced to a large extent in the current developing and threshold nations in the Asian/Pacific region. Forecasts indicate a 50% share of the global mobile communications market for this region by 2015. Similar growth rates are expected for Eastern Europe and Central and South America. The "classical industrial countries" in North America and Europe (EU15) will only have a slight increase in subscriber numbers from 2005 because, with penetration rates of more than 80%, saturation will be approached. North America and EU15 will only have shares of the world's subscribers of about 7% and 11% respectively by 2015 according to forecasts. One result of the immense growth rates will be a steep rise in the demand for additional radio resources the necessity for very efficient usage of the radio resources. There is constant increase in global demand for data transfer, record growth in Internet links and access together. With the requirement to make these services in the fixed network sector as well in the mobile sector, all forecasts are predicting a steep rise in the volume of data transfers using mobile communication systems. Although the demand for mobile computing, Internet and intranet access already exists, expansion in these sectors was greatly hindered by cumbersome equipment, very low data transfer rates and overly expensive costs for the mobile transfer of data. All of these barriers are set to be overcome in GSM Phase 2+ and by the 3G systems. Against this background, the expert studies (for example, UMTS Forum) are predicting a considerably greater increase in the volume of data for transfer than for speech transmissions. While annual growth in speech transmission in industrialized nations in the coming years is predicated to be between 20% – 60%, a significant growth rate of more than 100% is expected for the volume of data to be transferred. Between the years 2005 and 2007, the data transfers are predicted to make up about 50% of the total traffic – with an upward trend in the years thereafter. This means that all forecasts envisage data transfers taking the lion's share in the medium term. Current Market Demands Regarding Mobile Communications The demands currently made by the mobile communications market are varied and include the following: 1. 2. 3.
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Improved speech quality User friendliness Global accessibility
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Trend: Speech to Data Transmission
Overview of UMTS Technology and its Evolution
4. 5. 6. 7. 8. 9.
Special services for particular user groups (for example, Closed User Groups) Flexible Service Creation Everywhere the same services as in HPLMN Fast transfer of large data volumes Mobile Internet / Intranet Access Multi Media capabilities
3.3
3G end-to-end IP Solutions
With UMTS Release 99, a radio interface solution was introduced to allow the transport of a wide range of multimedia services. The transmission network solution of the UMTS radio access network is based on ATM (and an alternative specification of IP transport partly exists), which guarantees flexible bearer establishment in the radio access network.
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However, the UMTS CN solution is still rooted in GSM, and this may impose limitations for multimedia applications. In UMTS Rel. 4 and 5, call-processing server solutions combined with media gateways were specified for circuit and packet switched services to allow flexible bearer establishment also in the core network. The specifications explicitly mention IP and ATM as potential transmission solutions for the core network. This means a core network evolution. The following diagram illustrates the use of IP for the network traffic:
Fig. 9 3G IP – Majority of the traffic over IP
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Overview of UMTS Technology and its Evolution
The majority of the traffic is expected to be packet switched data transfer over IP. The IP is expected to fully support mobility management provided, if expressed in telecommunication terms. Additionally, in this kind of environment the IP must fully support QoS thinking. These two conditions are essential if cellular IP terminals are going to be used. 3G – Services & Required Data Rates Different services have different requirements regarding the appropriate data rate. Only a few kbit/s are required for conventional voice transmission with the use of efficient speech data compression functions. Data rates to the order of several 10 kbit/s are helpful and meaningful for convenient e-mail transfers. Greater bandwidth ranging from several kbit/s to more than 100 kbit/s is required for efficient general data transmissions, Internet access, mobile banking, shopping, etc.
UMTS will be able to dynamically and flexibly provide these data rates ranging from 8 kbit/s to a maximum of 2 Mbit/s. The following diagram illustrates the services provided by the 3G:
Fig. 10 The services provided by the 3G
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Even greater data rates from several 10 kbit/s to several 100 kbit/s are necessary for high-quality image transmission and video telephony. The highest requirements for data rates from 100 kbit/s to more than 1 Mbit/s are demanded by video conferences and video-on-demand applications, in addition to different multimedia applications.
Overview of UMTS Technology and its Evolution
3.4
Specification Process for UMTS
As the 3G system is expected to be global, world-wide, and generic, the specification bodies related are also global ones as discussed following section. In addition to the specification bodies, the specification process includes co-operation of operators and manufacturers. The following international standardisation bodies are acting as “generators” for 3G specification work: International Telecommunication Union (ITU-T) This organisation provides in practise all the telecommunication branch specifications that are official in nature. Hence, these form all the guidelines required by the manufacturers and country-specific authorities. ITU-T has finished its development process for, International Mobile Telephone – 2000 (IMT2000). IMT-2000 represents a framework on how the network evolution from a second to a third generation mobile communication system shall take place. Even more important, different radio interface scenarios were outlined for 3G systems. European Telecommunication Standard Institute (ETSI) zezenenu.und.lmm/tuxonuqu.en.slo
This organisational body has had a very strong role when GSM Specifications were developed and enhanced. ETSI is divided into workgroups named SMG (number), and every workgroup has a specific area to develop. Because of the GSM background, ETSI is in a relatively dominant role in this specification work. Alliance of Radio Industries and Business (ARIB) ARIB conducts studies and R&D, establishes standards, provides consultation services for radio spectrum coordination, cooperates with other overseas organizations and provides frequency change support services for the smooth introduction of digital terrestrial television broadcasting. These activities are conducted in cooperation with and/or with participation by telecommunication operators, broadcasters, and radio equipment manufacturers. American National Standard Institute (ANSI) ANSI is the American specification body that has issued a license for a subgroup to define telecommunication-related issues in that part of the world. Because of some political points of view, ANSI’s role is relatively small as far as UMTS concerned. The ANSI subgroup is mainly concentrating on a competing 3G air interface technology selection called cdma2000. In order to maintain globalisation and complete control of the UMTS specifications, a separate specification body called 3GPP (3rd Generation Partnership Project) was established to take care of the specification work in co-operation with the previously listed institutes. The outcome of the 3GPP work is a complete set of specifications defining the 3G network functionality, procedures, and service aspects.
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Overview of UMTS Technology and its Evolution
The following diagram illustrates 3GPP:
As there are some political desires involved, the issue is not as simple as described; global system means global business and this is why there has been a lot of pressure to select or emphasise certain solutions more than others. This political debate actually delayed the specification work remarkably, and finally an organisation was established to take care of the harmonisation issues. This organisation, Operator Harmonisation Group (OHG) aims to find a common understanding concerning the global issues. The results of this organisation are used as inputs in 3GPP work as well as in 3G future implementations. The OHG made its may be the most remarkable decision in April-May 1999, when it decided the common-for-all-variants code word (chip) rate in the 3G WCDMA air interface. This issue has a direct effect on the system capacity and implementation and it was maybe the biggest delaying factor concerning the UMTS specifications. The aim of the OHG work is to affect the specifications so that all radio access variants are compatible with all the variants meant for switching, this will ensure true globalisation for 3G systems. The first UMTS release was frozen in December 1999. This release is called UMTS Release 99. In UMTS Release 99, the specification body 3GPP concentrated on following two main aspects: Inauguration of a new radio interface solution. A new 3G radio interface solution must use the radio interface resources more efficient than it is the case with 2G radio interface solution. In addition to that, it must be very flexible in terms of data rates to allow a wide range of applications to be served.
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Fig. 11 3GPP –standardisation body for UMTS
Overview of UMTS Technology and its Evolution
The UMTS radio interface solutions are based on the multiple access principle CDMA. CDMA stands for Code Division Multiple Access. In UMTS Release 99, CDMA is applied on 5 MHz carrier frequency bands. This is the reason, why in some areas of the world, UMTS is called Wideband CDMA (WCDMA). Following radio interface solutions were specified with UMTS Release 99: 1.
The FDD-mode combines CDMA with frequency division duplex, i.e. uplink and downlink transmission are realised on separate 5 MHz frequency carriers.
2.
The TDD-mode combines CDMA with time division duplex, i.e. uplink and downlink are made available of the same 5 MHz frequency carrier, separated in time.
The next version of the 3GPP Specifications is Release 4, which was frozen March 2001, and Release 5, which was frozen in March/June 2002. In Release 4 and 5, the upgrades in the radio access and radio access network were minor. The main focus lay on the core network and the service infrastructure.
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UMTS Release 4 included a specification of the Multimedia Messaging Service (MMS), a new radio interface solution for China called low chip rate TDD mode (or TD-SCDMA). While in UMTS Release 4 the first steps toward a ‘3G All IP’ could be found, this was fully specified in UMTS Release 5, including the IP Multimedia Subsystem (IMS).
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Overview of UMTS Technology and its Evolution
4
Evolution of UMTS Technology
The follwoing topic discuss about the evolutionary path of GSM to UMTS technology and list significant events in the evolution of CDMA networks.
4.1
GSM & UMTS Evolution
The original plans for GSM in the 1980's included all aspects of a 2G standard. In 1988 it became clear that this was not possible in the specified time frame. For this reason, GSM was released in a preliminary version in 1990/91 as GSM Phase 1.
4.1.1
GSM Phase 1
4.1.2
GSM Phase 2
After Phase 1completion, the GSM Standard was fully revised. Phase 2 includes a wide range of supplementary services comparable with the ISDN standard.
4.1.3
GSM Phase 2+
Phase 2+ enhances in Annual Releases (`96, `97, `98, `99) the GSM standard and prepares the UMTS introduction. Especially the GSM Core Network (CN) is enhanced to be used as UMTS CN at UMTS start. Major Phase 2+ aspects are IN services, flexible service definition, packet data transfer, high data rate transmission and improved voice codes. GSM is limited by the narrowband radio access, the radio resource efficiency and a lack of additionally available frequency bands.
4.1.4
UMTS Release `99 (also: Release 3)
With GSM Rel. `99, a handshake with the first UMTS Release (Rel`99 or Rel. 3) according to many CN and service aspects is performed. UMTS introduces a new, broadband radio access optimized for packet data transmission up to 2 Mbit/s.
4.1.5
UMTS Release 4
Unlike GSM Phase 2+, the enhancement of UMTS is not performed in annual steps. Enhancements should be possible in flexible time schedules. Rel. 4 (March 2001) introduces for example, important CN modifications (bearer independent signaling flow) and the Low Chip Rate LCR TDD mode as a third radio access
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Phase 1 contains everything required for the operation of GSM networks. Speech data transfer is the core focus. Data transfer is defined, too (0.3 - 9.6 kbit/s). Only a few supplementary services are included.
Overview of UMTS Technology and its Evolution
option.
4.1.6
UMTS Release 5
For UMTS Rel. 5 major CN modifications, i.e. the IP Multimedia Subsystem (IMS) are planned. New network elements and protocol structures are defined.For the future modifications of the UMTS Terrestrial Radio Access Network (UTRAN) toward an All IP RAN, enhancements of the radio resource efficiency, new frequency ranges (WRC'2000) and many more enhancements toward 4G are expected. The following figure illustrates GSM and UMTS Evolution:
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Fig. 12 GSM and UMTS Evolution
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Overview of UMTS Technology and its Evolution
4.2
Data Transmission Evolution
In Phase 2+ HSCSD, GPRS, and EDGE are introduced to enhance the data transmission capabilities.
4.2.1
High Speed Circuit Switched Data (HSCSD)
HSCSD defines bundling of up to 8 physical channels of one carrier. In practice, however, only up to 4 channels are bundled together due to CN restrictions. The maximum data rate per physical channel was increased from 9.6 kbit/s to 14.4 kbit/s, introducing a new codec. As a result, up to 57.6 kbit/s can be reached (theoretically up to 115.2 kbit/s). HSCSD, like conventional GSM, defines Circuit Switched CS data transfer. For HSCSD, only minor modifications to the GSM network were necessary.
General Packet Radio Services (GPRS)
GPRS also allows bundling of up to 8 physical channels to one user. Four new Coding Schemes CS enable transfers at rates of 9.05 /13.4 / 15.6 / 21.4 kbit/s per physical channel. GPRS introduces Packet Switched PS data transmission, which allows efficient use of resources and direct access to Packet Data Networks PDN. New network elements and protocols, paving the way for UMTS, have been defined.
4.2.3
Enhanced Data Rate for the GSM Evolution (EDGE)
EDGE introduces a new modulation method over the radio interface: 8-Phase Shift Keying (8PSK). This allows three times faster data transfer compared to the conventional GSM modulation method Gaussian Minimum Shift Keying GMSK. In this way, EDGE is used to enhance the performance of GPRS and HSCSD. Transmission at up to 69.2 kbit/s per physical channel is possible. Theoretically, data rate of up to 553.6 kbit/s are possible, granting ITU 3G requirements for Zone 3 wide area mobility.
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4.2.2
Overview of UMTS Technology and its Evolution
4.2.4
High-Speed Downlink Packet Access (HSDPA)
HSDPA is protocol belonging to the High-Speed Packet Access (HSPA) family of protocols. HSDPA is a third generation (3G) mobile telephony communications protocol which provides high speed data transfer and capacity to UMTS based networks. HSDPA can support data rates of upto 10.8 Mbps and simultaneously co-exist with R99 in the same frequency band of 5MHz. HSDPA is capable of catering to some of the most demanding Multimedia applications. The maximum speed provided by HSDPA in the 5MHz channel is nearly around 10Mbps. However, apart from peak rate or maximum speed provided by HSDPA, more advantageous is the throughput capacity that shows a phenomenal increase. As a result of this, higher and higher number of users can make use of the high data rates on a single carrier.
4.2.5
High-Speed Uplink Packet Access (HSUPA)
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HSUPA is protocol belonging to the High-Speed Packet Access (HSPA) family of protocols. HSUPA is a third generation (3G) mobile telephony communications protocol which provides a maximum uplink speed of 5.76 megabits per second (Mbps). HSUPA improves the performance of the enhanced dedicated channel (E-DCH) by increasing throughput and reducing delays. The link-adaptation in HSUPA is quicker and therefore it reduces latency and improves performance.
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Overview of UMTS Technology and its Evolution
5
Existing GSM and UMTS Service Concept
5.1
User Services
Subscribers are paying for value added services offered to them. Therefore mobile operators are currently concentrating in broadening the services, offered to the subscribers. Following are the some of the examples: E-mail. Telecommuting. Multimedia messaging. Improved quality of service. Support for video and audio clips. Simplified service provisioning and service upgrades through the capability to download new service applications with minimal customer interaction. Enhanced user service management covering the ability to customise and configure the appearance and behaviour of user services and applications. This management may include user interface customisation where the terminal supports that capability. Access to a complete range of integrated, customer-friendly services customised to their needs by operators and service providers. These services will be available irrespective of the serving network and terminal, assuming that similar capabilities are available. Where the capabilities are not available, the user will be presented with a subset of the service.
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Wireless personal Internet-information anywhere at anytime.
Overview of UMTS Technology and its Evolution
5.2
GSM Service Support in UMTS
The Tele Services TS, Bearer Services BS and Supplementary Services SS of GSM Phase 2+ are defined, supported and enhanced in and for UMTS (TS 22.004). These experienced "classical" service concept with services of strictly defined functionality will built a platform of uniform (i.e. offered to all subscriber world-wide in the same way) services for GSM and UMTS users. Nevertheless, this strict service definition disables to create flexible new operator specific services. Demands on market differs much more on a global market and standardization in 3GPP will not be fast and flexible enough to satisfy changing regional market demand and follow all technical changes. Therefore, with the Virtual Home Environment (VHE), TS 22.121, a flexible concept for service creation has been developed for enhanced GSM networks and UMTS infrastructure.
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Overview of UMTS Technology and its Evolution
5.3
WCDMA in UMTS
WCDMA for UMTS has several advantages, for example: Efficient use of the radio frequency spectrum Different technologies, which improve the spectrum usage, are easy to apply to CDMA. For example, in GSM, one physical channel is dedicated to one user for speech transmission. If discontinuous transmission is applied, several timeslots of the physical channels are not used. These timeslots cannot be used otherwise. In UMTS, the transmission of several mobile phones takes place on the same frequency band at the same time. Therefore, each transmission imposes interference to the transmissions of other mobile phones on the same carrier frequency band. UMTS supports discontinuous transmission via the radio interface.
Limited frequency management CDMA uses the same frequency in adjacent cells. There is no need for the Frequency Division Multiple Access (FDMA) / Time Division Multiple Access (TDMA) type of frequency assignment that can sometimes be difficult. This is the main reason for increased radio interface efficiency of WCDMA. Low mobile station transmit power With advanced receiver technologies, CDMA can improve the reception performance. The required transmit power of a CDMA mobile phone can be reduced as compared to TDMA systems. In the FDD mode, where bursty transmission is avoided, the peak power can be kept low. Continuous transmission also avoids the electromagnetic emission problems caused by pulsed transmission to, for example, hearing aids and hospital equipment.
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Consequently, if mobile phones are silent, when there is nothing to transmit, the interference level is reduced and therefore the radio interface capacity increased. Another option allowed in UMTS is the multiplexing of packet switched traffic with circuit switched traffic. If there is no speech to transmit for a subscriber, the silent times are used for packet switched traffic.
Overview of UMTS Technology and its Evolution
Uplink and downlink resource utilisation independent Different bit rates for uplink and downlink can be allocated to each user. CDMA thus supports asymmetric communications such as TCP/IP access. Wide variety of data rates The wide bandwidth of WCDMA enables the provision of higher transmission rates. Additionally, it provides low and high rate services in the same band. Improvement of multipath resolution The wide bandwidth of WCDMA makes it possible to resolve more multipath components than in 2nd generation CDMA, by using a so-called RAKE receiver. This assists in lowering the transmit power required and lowers interference power at the same time. The result is further improved spectrum efficiency. Statistical multiplexing advantage The wideband carrier of the WCDMA system allows more channels/users in one carrier. The statistical multiplexing effect also increases the frequency usage efficiency. This efficiency drops in narrowband systems with fast data communications, because the number of the users on one carrier is limited. Increased standby time from higher rate control channels zezenenu.und.lmm/tuxonuqu.en.slo
The wideband carrier can enhance the transmission of the control channels. The MS only listens to the control channels part of the time, thereby increasing the standby time.
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Overview of UMTS Technology and its Evolution
5.4
Flexible Service Creation
The (GSM/UMTS) network offers service elements, which are used by applications. The applications form the value added for the subscriber (see also Next Generation Network Group). A set of services have been made available by UMTS.
5.4.1
Customized Applications for Mobile Network Enhanced Logic (CAMEL):
5.4.2
Mobile Station Application Execution Environment (MExE):
MExE introduces an open architecture for flexible support of Internet contents transmission in GSM / UMTS (Rec. 22.057, 23.057). It contains mechanisms for downloading information and applications to the User Equipment UE. It creates a suitable environment for implementing the applications. UE's indicate their capabilities to the network, transmitting their MExE classmark at connection setup. Following are the two techniques that can be applied for MExE:
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1.
Wireless Application Protocol (WAP) was developed by the WAP Forum. WAP is an open industry standard allowing the use of Internet information regardless of the access technology used. WAP is optimized for MS with a small display and uses the Wireless Markup Language (WML) format for representing IP data.
2.
JAVA will continue to be used because of its universality, platform independence and its inherent ability to recognize networks.
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The support of IN (Intelligent Network) services on non-proprietary basis in GSM & UMTS is introduced with CAMEL (3GPP TS 22.078, 23.078). Previous IN solutions for GSM were of a proprietary nature and could therefore only be used by subscribers in the home PLMN (HPLMN). CAMEL allows the global use of IN services (if the Visited PLMN supports CAMEL). Operator-specific services, based on the VHE / OSA concept of ÚMTS / GSM can be implemented using CAMEL. CAMEL has been introduced in three phases (GSM Rel. '96, '98 and '99); UMTS directly adopts the CAMEL Phase 3 solution for UMTS Rel. '99.
Overview of UMTS Technology and its Evolution
5.4.3
UMTS Subscriber Identity Module Application ToolKit ((U)SIM ATK):
The (U)SIM ATK defines commands for interactions between the Mobile Equipment(ME) and the SIM card (Rec. 22.038, 03.48, 31.102 and 31.111). Applications can be downloaded onto the (U)SIM card with the toolkit. Greater memory capacities than before are needed (and offered today) on (U)SIM cards. The (U)SIM ATK applications are logically separate from previous GSM functionalities on SIM cards and are controlled by subscribers using menus. SMS or packet data transmission in GPRS/UMTS can be used to download new software or applications for the (U)SIM ATK from a server to (U)SIM cards or for the communication between these elementsin general. Examples of (U)SIM ATK applications are mobile banking, mobile flight booking, etc.The (U)SIM ATK contains new security mechanisms for these applications.
5.4.4
Virtual Home Environment (VHE):
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VHE (TS 22.121, 23.127) is defined as a concept for Personal Service Environment (PSE) across network boundaries and between terminals. The concept of the VHE is such that users are consistently presented with the same personalized features, User Interface customization and services in whatever network and whatever terminal (within the capabilities of the terminal and network), where ever the user may be located.
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Overview of UMTS Technology and its Evolution
5.4.5
Open Service Architecture (OSA):
OSA (TS 23.127) defines an architecture that enables operator and 3rd party applications to make use of network functionality through an open standardizedApplication Programming Interface API: OSA API. OSA provides the glue between applications and service capabilities provided by the network. In this way applications become independent from the underlying network technology. The applications form the top level of the OSA. This level is connected to the Service Capability Servers SCSs via the OSA API. The SCSs map the OSA API onto the underlying telecom specific protocols (for example, MAP, CAP etc.).
Mobile commerce (mCommerce) In near future, mobile phones will become the personal trusted device that enables mobile commerce. With UMTS, the type and variety of mobile commerce transactions increases significantly, becoming a way of life for every day needs. Some examples of every day needs are local payments, online banking, music purchases and downloads, as well as ticketing. Also advertising will become an important part of overall mCommerce. Trust of brand for providing the mobile commerce service together with transaction security are two essential factors ensuring the acceptance and growth of mobile commerce. Mobile commerce solution addresses the three key elements of secure transactions: 1. 2. 3.
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Confidentiality, meaning those contents of the transaction can not be seen by any outsider. Integrity, meaning that the parties performing the transaction can be sure of that the other party is the one he/she claims. Irrevocability, meaning that either party after performing the transaction can not claim the transaction has not been performed.
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They hide the network complexity from the applications. Applications can be network/server centric applications or terminal centric applications. Terminal centric applications (for example, MExE and USIM ATK) reside in the UE. Network/server centric applications are outside the Core Network (i.e. the applications are executed in Application Servers that are physically separated from the CN entities) and make use of service capability features offered through the OSA API.
Overview of UMTS Technology and its Evolution
6
New Evolutions
6.1
IPTV
An IPTV solution delivering video services over a telecom infrastructure has to compete with well-known and established terrestrial, satellite or cable services with respect to broadcast channel contents, deliverable services and performance benchmark. A significant advantage that Telco operators have is the ability to provide complete entertainment and communication solution over a single broadband access network. Technology evolvement has contributed significantly to the success of such solutions. The evolution of xDSL technology e.g. ADSL2+/VDSL/VDSL2 towards higher and higher bandwidth allows rich content and multimedia services to be delivered. Another contributing factor is improvement in compression technology. MPEG-2 with advance coding can now produce reasonably good quality pictures at low bitrates. The emergence of MPEG-4 AVC (Advanced Video Coding) and WM9 will further strengthen this growth. zezenenu.und.lmm/tuxonuqu.en.slo
6.1.1
Services of IPTV
Digital broadcast TV This IPTV service allows subscribers to view digital TV broadcast channels in real-time streaming over their broadband connection. The user can change channels with the up/down or number buttons on the remote control. The service supports information overlay such that when a channel is selected an information banner appears at the bottom of the screen providing channel information and program synopsis. There is full flexibility in configuring packages of channels, allowing the operator to offer any number and combination of basic and premium channel packages. Digital Radio and Music Broadcast (DMX) DMX allows a service provider to stream radio stations through the broadband infrastructure. The subscriber can select “Digital Radio” from the main menu of the graphical user interface (GUI). After selecting this item, he will then be able to choose one of the provided radio channels using the remote control in the same manner as for DTV channel selection.
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Overview of UMTS Technology and its Evolution
Video on Demand (VoD) Video on Demand is provided with full VCR-like controls with capability to play, pause, fast-forward (multiple scan rates), fast-rewind (multiple scan rates) and direct jump to a particular part of a movie. It is possible to stop a movie and return to the same point at a later time. In order to facilitate movie browsing, videos are categorized into well-known genres that are available at the top level of the VoD EPG. Electronic Programming Guide (EPG) The EPG provides programming information for digital broadcast television, music and PPV. The EPG look and feel is also replicated across the VoD and Walled Garden content directories. For real-time programming the EPG provides 7 days of programs information including detailed synopsis of each programs.
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Fig. 13 DTV and Music
Overview of UMTS Technology and its Evolution
Fig. 14 Electronic Programming Guide (EPG)
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Internet on TV Internet access is provided on the television by using a web browser customized for TV use. This web browser is integrated into the client software residing on the STB. With an optional keyboard, subscribers can surf in the internet in as similar fashion as if they were using a PC. However, this application is not meant as a full substitution for internet browsing on a PC. E-Mail via HTML With the web over TV feature described above, it is also possible for the users to access an e-mail account via HTML, reading and writing e-mails via a web-based e-mail server. An optional keyboard is recommended to use this feature. Gaming on demand This application enables the user to play single-player games running locally on the STB using the STB’s java virtual machine The games are held as long as the browser is open; once it is closed the games are lost and need to be downloaded again from the network. The user is able to play the games using just the remote control.
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Overview of UMTS Technology and its Evolution
Video telephony This service is part of the NGN solution and provides means to conduct video telephony i.e. “point to point” video and voice transmission over an IP network. The solution requires a stand-alone web camera (USB connection) or one that is integrated with STB. For true video conferencing (point to multipoint – up to 16 sessions), additional equipment (Radvision) is required. This service allows for a SIP/IP based video and voice communication between two users. Both video and voice data are encoded at the STB and sent via IP to the peer user.
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Fig. 15 Gaming on Demand
Overview of UMTS Technology and its Evolution
6.2
WiMAX
WiMAX (Worldwide interoperability for Microwave Access) is a broadband wireless technology which is used to deliver broadband access services to residential and enterprise customers in an economical way. WiMAX is a wireless industry coalition whose members organized to advance IEEE 802.16 standards for broadband wireless access (BWA) networks. Some supplemental specifications have also been created by the WiMAX Forum. WiMAX operation is similar to WiFi but WiMax operates at higher speeds, can be provided over greater distances and can be provided to a greater number of users. WiMAX 802.16 technology is expected to enable multimedia applications with wireless connection and, with a range of up to 30 miles, enable networks to have a wireless last mile.
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Fig. 16 4G Candidate
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Overview of UMTS Technology and its Evolution
6.2.1
WiMAX Speed and Range
WiMAX is expected to offer initially up to about 100 Mbps capacity per wireless channel for portable applications and upto 1Gbps for fixed applications. WiMAX provides support for Internet data and voice and video. WiMAX could potentially be deployed in a variety of spectrum bands: 2.3GHz, 2.5GHz, 3.5GHz, and 5.8GHz. WiMAX utilizes OFDM in order to serve multiple users. WiMAX serves these users in a time division fashion using a round-robin approach. This service to the users is so fast that users often tend to believe that the transmission and receipt of data is continuous. Why WIMAX? WiMAX offers access solution to various different requirements. Applications that can use WiMAX extend broadband capabilities to: Get closer to subscribers Fill gaps in cable DSL and T1 services, Wi-Fi and cellular backhaul, Provide last-100 meter access from fibre to the curb Give service providers a cost-effective solution to support broadband services
WiMAX provides support to solutions that need a high amount of bandwidth, which requires large spectrum deployments (i.e. >10 MHz). WiMAX can accomplish this in the existing infrastructure thereby lowering implementation costs required to deliver bandwidth for high-value, multimedia services.
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Fig. 17 WiMAX Standards and Standards Group
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WiMAX comes as a cost effective solution to service providers who have to cater to increasing customer demands as it seamlessly interoperates across different networks without requiring any enhancements to the existing infrastructure. WiMAX also provides wide area coverage and quality of service capabilities for different types of applications. These applications include real-time delay-sensitive voice-over-IP (VoIP), real-time streaming video and non-real-time downloads. Using WiMAX for these applications delivers expected performance for all types of communications over the network. WiMAX seamlessly integrates with both wide-area third-generation (3G) mobile and wireless and wireline networks. This allows WiMAX to become part of a seamless anytime, anywhere broadband access solution.
6.2.2
Benefits of WiMAX
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WiMAX provides different benefits to the different section of customers it caters to. For instance, for component makers it creates a volume opportunity for silicon suppliers. Equipment makers benefit because WiMAX provides them a standards-based, stable platform allowing them to innovate more rapidly. With WiMAX, equipment makers can use the stable platform for adding new capabilities to an existing solution instead of starting from scratch for a new solution. The different benefits provided to Operators include a common platform which allows operators to reduce the cost of installing more equipments. This directly has an impact on performance, which cannot be achieved with proprietary approaches. WiMAX also provides a new avenue for business by filling broadband access gaps. Operators can use WiMAX to provision T1 / E1 level and high margin broadband services on an on-demand basis. Operators also benefit from the fact that base stations can interoperate with multiple vendors' CPEs and they are not bound to a single vendor. Consumers benefit from the choices provided in aread where there were gaps earlier. These include areas such as worldwide urban centers where building access is difficult; suburban areas where subscriber is located at a longer distance from the central office; and poorly connected rural and low population density areas. Additionally, competition amongst operators will reduce the monthly subscription costs. WiMAX is a IP-based wireless broadband access technology based on IEEE 802.16 specifications which provides an alternative to cable and DSL. The design of WiMAX network follows five principles which include spectrum, topology, internetworking, IP connectivity and mobility management.
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6.2.3
IP-based WiMAX network model
The IP-based WiMAX network model was developed by the WiMAX Forum NWG. This model describes a number of functional entities and interfaces between them. This model is based on a unified network architecture which provides support for fixed, nomadic, and mobile deployments. Logically, the network can be divided into three parts, Mobile Station (MS), access service network (ASN) and Connectivity service network (CSN). An end user uses MS to access the network. One or more MS together with one or more ASN gateways contained in the ASN form the radio access network at the edge. CSN provides IP connectivity and IP core network functions. The Base station provides air interface to MS and also performs additional Micromobility management functions. Some of these functions include:
ASN gateway perform the function of a layer 2 traffic aggregation point within an ASN. Additional functions of ASN gateway include: Foreign agent functionality for mobile IP QoS and policy enforcement AAA client functionality Radio resource management and admission control Caching of subscriber profiles and encryption keys Establishment and management of mobility tunnel with base stations Routing to the selected CSN Intra-ASN location management and paging
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Establishment of tunnel DHCP (Dynamic Host Control Protocol) proxy Handoff triggering QoS policy enforcement, Traffic classification, Management of radio resource, key, session and multicast groups
Overview of UMTS Technology and its Evolution
CSN provides connectivity public and corporate networks and the Internet. The CSN is owned by NSP and includes AAA servers that support authentication for the devices, users, and specific services. CSN provides the following functionalities: Per user policy management of QoS and security IP address management Support for roaming between different NSPs Location management between ASNs Mobility and roaming between ASNs NSN WiMAX is being designed to meet the most stringent prevailing industry requirements. This includes the WiMAX standards that have been approved and promulgated by the IEEE and the supplemental specifications that have been created by the WiMAX Forum. The NSN WiMAX system will meet the requirements of IEEE 802.16-2004 for fixed arrangements and 802.16e-2005 for portable and low-mobility systems in Release 1. Nokia is a founder and active member of the WiMAX Forum, which was formed in June of 2001 to foster conformance and interoperability of the IEEE 802.16 standard. zezenenu.und.lmm/tuxonuqu.en.slo
The WiMAX Forum has further defined WiMAX requirements by publishing documents that cover the areas of: frequency band allocations channel bandwidth configurations application profiles to support interoperability end-to-end network architecture
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6.3
Long Term Evolution (LTE)
LTE is 3GPP system for the years 2010 to 2020 and beyond and is expected to be ready for commercial launch by 2010. This system is being developed to especially compete with WIMAX 802.16e/m. LTE maintains support for high and highest mobility users like those in GSM/UMTS networks. The architectural changes made in LTE are big as compared to UMTS. The work on evolution of 3G cellular technology started with a workshop held in Toronto, Canada in November 2004. This workshop identified the need to come up with a new technology. Some requirements that came up for this new technology included the following:
6.3.1
Why LTE (Drawbacks of 3G)
The maximum bit rates still are factor 20 and more behind the current state of the art systems like 802.11n and 802.16e/m. Even the support for higher mobility levels is not an excuse for this. The latency of user plane traffic (UMTS: >30 ms) and of resource assignment procedures (UMTS: >100 ms) is too big to handle traffic with high bit rate variance efficiently. The terminal complexity for WCDMA or MC-CDMA systems is quite high, making equipment expensive, resulting in poor performing implementations of receivers and inhibiting the implementation of other performance enhancements like MIMO for a lot of equipment.
6.3.2
Benefit of LTE
With the ever-increasing demand for improved wireless broadband that provides same experience and applications as provided by wireline connections, companies are looking at taking advantage of technology innovation to improve economics of deploying mobile broadband networks. A new technology that is better than the existing 3G and 2G networks will provide wireless service providers a new revenue source. LTE comes as a solution here. Apart from enabling fixed to mobile migration of Internet applications, LTE can also support an explosion in demand for connectivity from a new generation of consumer devices. LTE will provide its customers, whether individuals or business
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The new technology should reduce the cost on transferring every bit of data. The new technology should improve the quality of service given to users at a lower cost. The new technology should have the flexibility to use the existing as well as any new frequency bands. The new technology should have a simplified architecture and should have an open interface The terminal power consumption in the new technology should be reduced.
Overview of UMTS Technology and its Evolution
professionals all functionalities of a wireline connection over a wireless network giving them the ability to access any content, anywhere, irrespective or whether they are stationed at one location or mobile.
6.3.3
LTE Technologies
LTE is slated to support variety of network traffic ranging from mixed data, voice, video to messaging. Some major technological changes made by LTE include: OFDM (Orthogonal Frequency Division Multiplexing) MIMO (Multiple Input Multiple Output), which is an antenna technology similar to that used in IEEE 802.11n wireless local area network (WLAN) standard. System Architecture Evaluation (SAE), which will simplify the system as more and more IP data is used. LTE will use OFDM as the modulation format because OFDMA is suitable for carrying high data rates which is one of the primary requirements of LTE. In addition, OFDM is not affected to a great extent by interference and has been tested over the time with its usage in Wi-Fi and WiMAX.
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LTE will use MIMO for improved data throughput since MIMO provides a way of utilising the multiple signal paths that exist between a transmitter and receiver. MIMO will also improve the data capacity of the channel by allowing multiple data streams on the same channel. MIMO has also been tested over the times in its use in Wi-Fi and other wireless technologies. The basic work on LTE has not all been completed, some people anticipate that the first deployments may be seen in 2010. The initial drafts were released in September 2007 and the work on the infrastructure technology known as LTE System Architecture Evolution (SAE) had also stated after some time. Nevertheless 3G LTE is sure to happen and cellular technology will be in a position to offer much higher data rates than is possible today.
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7
Appendix
UMTS Specifications
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The specifications give detailed information on how services should be implemented into the network. The service classification of Release 2000 can be found from Specification 22.976. The below figure is taken directly from the specification and identifies where to find information on the types of services that have been covered in this module.
Fig. 18 Service classification, taken from Specification 22.976
In addition to the bearer description in the above figure, for more information on the VHE, refer to 22.970. This gives the overview of the specification and is useful in locating detailed information. For information on the wireless protocols of SAT and MExE, refer to the stage 1 (overview) specifications of 22.038 and 22.057 respectively. For more information on the supplementary services and the stage 1 specifications can be found in the range starting from 22.072 until 22.097. Stage 2 and stage 3 (implementation and technical realisation) can be found from the specifications, but the stage 1 should give you a start on how to find the desired information. Reference: Please refer to the following Nokia web site for the latest information. http://www.nokiasiemensnetworks.com
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WiMAX The Worldwide Interoperability for Microwave Access (WiMAX), is a telecommunications technology aimed at providing wireless data over long distances in a variety of ways, from point-to-point links to full mobile cellular type access. It is based on the IEEE 802.16 standard, which is also called WirelessMAN. The name WiMAX was created by the WiMAX Forum, which was formed in June 2001 to promote conformance and interoperability of the standard. The forum describes WiMAX as "a standards-based technology enabling the delivery of last mile wireless broadband access as an alternative to cable and DSL." Spectrum allocation issues
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The 802.16 specification applies across a wide swath of the RF spectrum, and WiMAX could function on any frequency below 66GHz"IEEE Standard for Local and metropolitan area networks Part 16: Air Interface for Fixed and Mobile Broadband Wireless Access Systems Amendment 2: Physical and Medium Access Control Layers for Combined Fixed and Mobile Operation in Licensed Bands and Corrigendum 1," IEEE Std 802.16e-2005 and IEEE Std 802.16-2004/Cor 1-2005 (Amendment and Corrigendum to IEEE Std 802.16-2004), 2006, pp. 3, (higher frequencies would decrease the range of a Base Station to a few hundred meters in an urban environment). There is no uniform global licensed spectrum for WiMAX, although the WiMAX Forum has published three licensed spectrum profiles: 2.3 GHz, 2.5 GHz and 3.5 GHz, in an effort to decrease cost: economies of scale dictate that the more WiMAX embedded devices (such as mobile phones and WiMAX-embedded laptops) are produced, the lower the unit cost. (The two highest cost components of producing a mobile phone are the silicon and the extra radio needed for each band.) Similar economy of scale benefits apply to the production of Base Stations. In the unlicensed band, 5.x GHz is the approved profile. Telecom companies are unlikely to use this spectrum widely other than for backhaul, as they do not own and control the spectrum.
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8
Exercises
Exercise 1 WAP/WTA was developed to: Support exclusively MexE. To design and program application locally on the ME. To allow interaction between the SCP and the ME. To support radio interface protocols.
Exercise 2 The abbreviation OSA stands for Open Systems Architecture. zezenenu.und.lmm/tuxonuqu.en.slo
a. True b. False
Exercise 3 Which of the following is, or will be, a characteristic of the Virtual Home Environment (VHE) (Choose two)? Allows the subscribers to use their services whilst roaming. It is only possible in UMTS. It is the same as a SMSC (Short Message Service Centre). VHE is possible because of CAMEL. VHE is located within the HLR. Enable the creation of services to the subscribers to customise their own environment.
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Exercise 4 A cluster is: A location area. An area of cells, where the hole set of frequency is used once. Cellular network of one operator. Coverage area of one BSC. Coverage area of one BTS.
Exercise 5 What does Handover means? Changing the cell during a connection. zezenenu.und.lmm/tuxonuqu.en.slo
Changing the area of one PLMN. Changing the location area. Changing the cell while there is no connection.
Exercise 6 How many HF channels do GSM 900 offers? 19 174 374 124
Exercise 7 Which features does not belong to GSM phase 2+? Blue Tooth ASCI
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HR EFR
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CAMEL
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8.1
Solutions
Exercise 1 (Solution) WAP/WTA was developed to: Support exclusively MexE. To design and program application locally on the ME. To allow interaction between the SCP and the ME. To support radio interface protocols.
Exercise 2 (Solution) The abbreviation OSA stands for Open Systems Architecture. zezenenu.und.lmm/tuxonuqu.en.slo
a. True b. False
Exercise 3 (Solution) Which of the following is, or will be, a characteristic of the Virtual Home Environment (VHE) (Choose two)? Allows the subscribers to use their services whilst roaming. It is only possible in UMTS. It is the same as a SMSC (Short Message Service Centre). VHE is possible because of CAMEL. VHE is located within the HLR. Enable the creation of services to the subscribers to customise their own environment.
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Exercise 4 (Solution) A cluster is: A location area. An area of cells, where the hole set of frequency is used once. Cellular network of one operator. Coverage area of one BSC. Coverage area of one BTS.
Exercise 5 (Solution) What does Handover means? Changing the cell during a connection. zezenenu.und.lmm/tuxonuqu.en.slo
Changing the area of one PLMN. Changing the location area. Changing the cell while there is no connection.
Exercise 6 (Solution) How many HF channels do GSM 900 offers? 19 174 374 124
Exercise 7 (Solution) Which features does not belong to GSM phase 2+? Blue Tooth ASCI
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HR EFR CAMEL
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UMTS Network Architecture
UMTS Network Architecture
Contents
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1
Module Objectives.....................................................................................2
2 2.1 2.2
UMTS Network Architecture.....................................................................3 Radio Network Elements.............................................................................5 Core Network .............................................................................................. 9
3 3.1 3.2 3.3
The UMTS Release 4 Architecture.........................................................24 Circuit Switched – Media Gateway (CS-MGW) ........................................ 26 Mobile Switching Centre Server ................................................................27 CAMEL Service Environment CSE ........................................................... 28
4 4.1 4.2 4.3 4.4
The UMTS Release 5 Architecture.........................................................30 IMS Reference Architecture...................................................................... 33 IP Multimedia Subsystem..........................................................................34 High Speed Downlink Packet Access....................................................... 37 The UMTS Evolution in Release 5............................................................40
5 5.1 5.2
The UMTS Release 6 Overview.............................................................. 42 Multimedia Broadcast Multicast Service................................................... 43 WLAN Interworking................................................................................... 44
6 6.1
Long Term Evolution.............................................................................. 46 System Architecture Evolution.................................................................. 48
7
Appendix.................................................................................................. 50
8 8.1
Exercises..................................................................................................51 Solutions....................................................................................................55
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1
Module Objectives
The aim of this module is to give the student the conceptual knowledge needed for explaining the UMTS-network architecture. Topics to be covered in this module include visualizing the whole network and identifying the elements of each subsystem. After completing this module, the participant should be able to:
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Briefly explain the network subsystems. Identify and list the requirements of UMTS mobile terminals. Identify and list the network elements used in Release 4. Identify and list the network elements used within the radio access network (RAN), in terms of the name and function. Identify the main functions of an RNC. Identify and list the network elements used within the core network. Briefly explain Intelligent Network (IN) and its function in 3G network. Briefly explain the IP Multimedia Subsystem (IMS) concept.
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UMTS Network Architecture
A Universal Mobile Telecommunications System (UMTS) network can be visualized from different angles, such as from the point of view of the user plane, control plane, or the function of each subsystem. In this module we will look at UMTS from the latter angle, where the focus is on the different network elements within the network. The UMTS network architecture can be divided into three subsystems: Radio Access Network. Core Network including the network elements for service groups. Network Management Subsystem. This separation will allow modularity in the composition of networks. The objective is to be able to combine any 3G CN with any 3G RAN. In addition, technical enhancements and updates of individual modules will be able to be introduced more easily, quicker and at less expensively due to the separation of functions.
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Each subsystem can be further divided into separate technologies. For example, the RAN (Radio Access Network) is compromised of different air interface technologies, such as GSM EDGE Radio Access Network (GERAN), UMTS Terrestrial Radio Access Network (UTRAN) and future solutions such as WLAN, 1ExTREME and 4G. The core network is today clearly divided into: Circuit Switched (CS) domain. Packet Switched (PS) domain. The network elements of the circuit switched domain are offering CS bearer services. They are inherited from GSM: MSC/VLR and GMSC. The packet switched domain is responsible to offer PS bearer services. Based on GPRS core network elements, the PS bearer services are currently non-real time services. But standards are on the way to enhance this infrastructure, so that also real-time services can be served via the PS domain transmission infrastructure. The CS and PS domains share some network elements. These common CS and PS domain network elements are the HLR, AC, and EIR. A set of service platforms was specified in GSM. These are now – in an enhanced version – also available in UMTS. Network elements for service groups include CAMEL, text telephony, Location Based Services (LBS) network elements. As can be seen service provisioning is partly located in the core network and contains all the service-enabling platforms that support the multitude of 3G services that an operator can offer. The UMTS specifications stipulated that the new air interface and system capabilities should reuse the existing 2G systems, such as GSM and GPRS. Therefore, it is envisaged that operators can quickly rollout network once the equipment is available. The standards dictate the configuration of the open
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UMTS Network Architecture
interfaces and the function of each subsystem; however, the implementation is vendor or operator specific. This has led into much more modular network architecture than we find in today's GSM networks. NSN fully supports open interfaces. The network elements are designed to be modular and are built in the manner that the functions can mature and evolve from new developments. Each year, the UMTS specifications are upgraded to support continuing functionality in the network. The next version of the specifications is known as UMTS Release 4 followed UMTS Release 5, Release6 and further.
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UMTS Release 4 will focus among others on having a specified IP or ATM Telephony Core. The focus of Release 5 is to have IP Multimedia Subsystem.
Fig. 1 UMTS Network Architecture
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2.1
Radio Network Elements
2.1.1
Node B
One or more Node B’s are controlled and addressed by an RNC. A Node B is a physical unit for implementation of the UMTS radio interface. It is converting the physical transmission of the data from fixed network transmission (ATM based) to WCDMA transmission. As a central transmission and reception site, it serves on or more UMTS cells. It is serving one UMTS cell in case of an omni cell with 360º service or, for example, 2, 3, or 6 sector cells with 180º 120º and 60º service respectively. The Node B is connected: via Iub interface to its controlling RNC via Uu interface to the UEs
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Fig. 2 Node B
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2.1.2
Radio Network Controller
The UMTS Terrestrial Radio Access Network (UTRAN) is sub-divided into Radio Network Subsystems RNS. The Radio Network Controller (RNC) is the central controlling unit of a RNS. It is controlling itself and all the Node Bs of the RNS. The RNC is connected via the following ATM based interfaces: Iub interface: to connected the Node Bs Iur interface: to neighboring RNCs Iu interface: to the Core Network CN Due to different protocol stacks, the Iu interface can be sub-divided into an Iu -ps interface and an Iu-cs interface.
The main task of the RNC is to perform Radio Resource Management RRM for all UEs in its service area. Therefore, it can be compared to the GSM BSC. Different to the GSM BSC, it is 100% autonomously responsible for all RRM decisions. RRM means to be that the RNC is responsible for signaling with the UEs via Radio Resource Control (RRC) protocol, it is deciding about the allocation of resources, Handover to other cells and release of resources, … The RNC is holding the RRC connection to the UEs as long as data have to be transmitted. It is storing the UEs location information to transmit the data to the right location. The location information can be requested by the CN for Location Based Services. It is responsible for reliable transmission over the radio interface, performing Backward Error Correction in acknowledged mode. It is responsible for Ciphering/De- Ciphering and Integrity Check.
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The Iu-ps interface is used for data and signaling transmission to the PS domain of the CN, the Iu-cs interface is used for data exchange with the CS domain.
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Fig. 3 Radio Network Controller zezenenu.und.lmm/ximemubi.en.slo
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2.1.3
User Equipment
The User Equipment UE is responsible for similar function as the GSM Mobiles Station MS, i.e., it is a device allowing a user access to network services. It consists of the: Mobile Equipment ME, which means to be the hardware and software for WCDMA air interface transmission. The ME is identified by an International Mobile Equipment Identity(IMEI).
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UMTS Subscriber Identity Module (USIM), which contains data and procedures, which unambiguously and securely identify itself. These functions are typically embedded in a stand-alone smart card. This device is associated to a given user (subscriber license), and as such allows to identify this user regardless of the ME he uses. The USIM stores the personal identities (e.g. IMSI, MSISDN, PIN), security algorithm (for e.g. Ciphering, Authentication), the personal phone book, the USIM Application Toolkit (USAT); TS 22.038, 31.111 and many more information.
Fig. 4 User Equipment
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2.2
Core Network
The UMTS networks are based on GSM Phase 2+ Core Networks. This approach safeguards the investments made by today's GSM network operators and reduces the 3G implementation risks. The UMTS Terrestrial Radio Access Network (UTRAN) is connected to the enhanced Phase 2+ Core Network(CN) via Iu interface. The GERAN and UTRAN can be connected to the same CN. The GSM Mobile Station (MS) is connected to the GERAN via GSM radio interface Um, the UMTS User Equipment (UE) to UTRAN via UMTS radio interface Uu. Important note: In order to allow a smooth evolution, some network elements are used in the 2G and 3G context, such as the MSC. In this material, it will be normally called MSC. If a specific reference to the second or third generation is required, it will be called 2G-MSC and 3G-MSC, respectively. The same is true for the SGSN. CS Domain The CS Domain of the UMTS CN consists of the following functions: MSC : Mobile Services switching Center zezenenu.und.lmm/ximemubi.en.slo
GMSC : Gateway MSC SMS-GMSC : Short Message Service Gateway MSC SMS-IWMSC : Short Message Service Interworking MSC VLR : Visitor Location Register TC/IWF : Transcoding & Interworking Function PS Domain The PS Domain of the UMTS CN consists of the following functions: GGSN : Gateway GPRS Support Node SGSN : Serving GPRS Support Node CGF : Charging Gateway Function BG : Border Gateway Function Entities common to the CS & PS Domain HLR : Home Location Register AUC : Authentication Center EIR : Equipment Identity Register CSE : CAMEL Service Environment UMTS Terrestrial Radio Access Network UTRAN & UE The UTRAN consists of the following functions: RNC : Radio Network Controller Node B UE : User Equipment
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2.2.1
Common UMTS Network Elements
2.2.1.1 IN Service The term Intelligent Network (IN) stands for IN solutions with INAP protocol (only in home PLMN) as well as for the CAMEL solution for international roaming. The IN platform provides the operators the tools for creating completely new services as well as full access to modify existing one, even on a subscriber basis. The highly scalable intelligent network platform offers the possibility to efficiently introduce and operate value adding intelligent services. The best example for this is the prepaid service in Mobile Network. Not only prepaid services can be built based on Mobile Network, but also are Virtual Private Network (VPN), Freephone, premium rate, split charging, and many more. Number Translation Services Number translation services comprise a group of very famous applications. The most important services are described here:
Freephone The freephone service is one of the most popular number translation services. Telephone charges are not billed to the caller but to the company being called. The company gets more calls, that means more business and the customers have a lower barrier to place a call.
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Fig. 5 UMTS Release 99 Core Network
UMTS Network Architecture
Universal Access Number As a service for companies with numerous branches or sales outlets, and especially for call centers, Universal Access Number offers distinct advantages. Car rental or service centers can give their customers a single, nationwide number, which automatically connects them to the nearest branch office. The caller dials, independent of his location, the same number and will be connected to the next service center. Premium Rate Service The Premium Rate Service, also referred to as Tele-info Service or Kiosk Service, enables service users to access the information offered by the service subscriber such as weather forecasts, stock rates or crossword puzzles. This is realized via the announcement facilities or interactive direct dialog. Televoting Depending upon the last digit(s) of the Televoting directory number dialed, the voting code, the calling party expresses his decision.
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Fig. 6 Number Translation Service
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Alternate Billing and Charging
Mobile Local Call Low-cost calls from mobile to fixed networks are currently extremely popular especially with people who mainly use their mobile phone within one regional area at any given time. This region can, of course, change. When the subscriber travels to another location he takes his 'local zone tariff' with him. The Intelligent Network automatically checks whether the person being called is indeed within the location of the mobile caller.
Virtual Card Calling People on the move want to make calls anytime, anywhere without having to have the right change at hand or pay exorbitant hotel rates. Virtual Card Calling allows subscribers to do just this. The subscribers have to enter a Credit Card Number+PIN or a Private phone number+PIN and the Intelligent Network checks the authorization of the caller. Prepaid Service The Prepaid Service is a real bestseller. For Prepaid services no contracts, no basic charges and no bills exist. The service provider does not know the customer. The service can also be used by travelers who are temporarily in a foreign country.
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Home Zone Billing The subscribers define various areas as their 'home zones' e.g. a 'business zone' for calls from the office, a 'residential zone' for calls from home and 'temporary zone' for spending short periods of time away. Home Zone Billing allows to define rates for mobile calls that are similar to the costs for fixed network connections.
UMTS Network Architecture
Fig. 7 Alternative Billing and Charging
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Fig. 8 Personal Services
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Personal Services
Personal Number Service This service guarantees for the subscriber that he can be reached on one single number at any terminal, regardless of whether it is in a fixed or in a mobile network. In his subscriber profile the subscriber also determines which calls must always be put through and which are to be rejected by diverting them to a voice mail system.
Friends and Family With Friends & Family, customers enjoy an especially attractive rate for the numbers they call most frequently. The subscriber can update the Friends & Family list at any time. The numbers and speed-dialing codes on the personal Friends & Family profile apply to fixed or mobile phones alike.
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Control of use The Control of Use service is an effective method of preventing the misuse of mobile phones. It works in such a way that the phone is only available to authorized user groups via a specific PIN code. Different PIN´s with different restrictions can be defined (e.g. no international outgoing calls, emergency numbers only,...)
UMTS Network Architecture
2.2.1.2 Home Location Register The Home Location Register (HLR) is a database in charge of the management of the mobile subscribers. There may be one or more HLRs in GSM PLMN The HLR is always associated with an Authentication Center (AC). It participates in different procedures, for e.g.: It sends all necessary data to the VLR. It supports the call setup in case of Mobile Termination Call (MTC) by sending routing information to the Gateway MSC (Interrogation). It transmits the security parameters from AuC to VLR on request. An HLR contains different semi-permanent mobile subscriber data, e.g.:
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IMSI: International Mobile Subscriber Identity MSISDN: Mobile Station International ISDN number Packet Data Protocol (PDP) address(es), e.g. IP address Services: Bearer Services (BS), Tele Services (TS), Supplementary Services (SS) A list of all the group IDs a service subscriber is entitled to use to establish voice group or broadcast calls CAMEL Subscriber Information(s) Service Restrictions (e.g. roaming limitations) Additionally, the HLR contains different temporary information of the mobile subscriber, e.g.: VLR and SGSN addresses Mobile station Roaming Number SMS flags The organization of the subscriber data is outlined in GSM 23.008
2.2.1.3 Authentication Center The Authentication Center (AuC) is responsible to store the secret Keys of the subscribers and the security algorithm, which are necessary for the generation of the GSM and UMTS security parameters. On request of the VLR respectively the SGSN the AuC generates the security parameters. They are delivered via HLR to VLR/SGSN to enable Authentication, Ciphering and Integrity Check. The AuC is connected only with the HLR via the non-standardised interface H. The HLR requests data for authentication and cipher setting from the AuC. The HLR can store this data, and makes it available to the VLR and SGSN on demand. The data delivered from the AuC is used for: Mutual authentication of the SIM-card (via IMSI) and the serving PLMN Delivering a key to check the communication integrity over the radio path between the user equipment and the VPLMN Ciphering over the radio path between the user equipment and the RNC.
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The AuC is responsible to store the secret Keys of the subscribers and the security algorithm, which are necessary for the generation of the GSM and UMTS security parameters. On request of the VLR respectively the SGSN the AuC generates the security parameters. They are delivered via HLR to VLR/SGSN to enable Authentication, Ciphering and Integrity Check.
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Fig. 9 Home Location Register and Authentication Center
2.2.1.4 Equipment Identity Register Equipment Identity Register (EIR) optional database is used to verify the International Mobile Equipment Identity (IMEI) numbers. The EIR is organised in three lists: 1. 2. 3.
Black list Grey list White list
The black list holds IMEIs, which are forbidden in the PLMN. The grey list holds IMEIs under supervision by law enforcement agencies, and the white list holds IMEIs, which are allowed to access the PLMN. A mobile phone can be also classified as to be unknown in the EIR. The interface F connects the EIR with the VLR, while the Gf interface links it with the SGSN. The EIR is connected to: The SGSN via Gf interface The VLR via F interface
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Fig. 10 Equipment Identity Register
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2.2.2
Circuit Switched UMTS Network Elements
2.2.2.1 MSC-Server The MSC-Server is responsible for all call control tasks of the MSC and VLR. Its tasks include the:
The MSC Server is connected to other network elements via the following interfaces: A-interface : to the GSM Base Station Controller BSC D-interface : to the HLR F-interface: to the EIR Gs-interface: to the SGSN Iu CS-interface: to the RNC Mc-interface: to the CS-MGW for separation between call control and bearer control. The ITU standard H.248 respectively its IETF standard equivalent Media Gateway Control (MEGACO) is used on Mc. Nc-interface: to GMSC Server for Bearer-Independent Call Control (BICC)
2.2.2.2 GMSC-Server The GMSC-Server adopts the call control tasks of the GMSC. Its tasks include: Interrogation of the HLR Termination of network-network signaling Interaction with the CS-MGW CDR collection The GMSC Server is connected to other network elements almost the same as MSC-Server.
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Call control of mobile originated and mobile terminated calls in the CS domain The VLR functionality. For all subscribers in the MSC-Server supply area, it holds temporarily the subscriber profile, location information, identities, etc. Interaction with the CS-MGW. The MSC-Server determines the QoS parameters required for the subscriber’s application. It is then the responsibility of the CS-MGW to make the bearer available. The interaction between MSC-Server and CS-MGW is done via an open interface, based on the ITU-T H.248 standard. Termination of UE-network and network-network signaling. The UE-network signaling is done via the Iu-CS interface. For the network-network signaling, signaling protocols such as the BICC (Bearer Independent Call Control) protocol can be used. CDR collection.
UMTS Network Architecture
2.2.2.3 Short Message Service SMS Gateway MSC (SMS-GMSC) The SMS-GMSC acts as an interface between an external Short Message Service Center SMS-SC and the PLMN, to allow short message to be delivered to MS/UE from the Service Center. The choice of which MSCs can act as SMS Gateway MSCs is a network operator matter (e.g. all MSCs or some designated MSCs)
2.2.2.4 SMS Interworking MSC (SMS-IWMSC) The SMS interworking MSC acts as an interface between the PLMN and a SMS-SC to allow short messages to be submitted from MS/UE to the SMS-SC. The choice of which MSCs can act as SMS Interworking MSCs is a network operator matter (e.g. all MSCs or some designated MSCs).
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Fig. 11 SMS-GMSC & SMS-IWMSC
2.2.2.5 Visitor Location Register The Visitor Location Register (VLR) is responsible to aid the MSC with information on the subcriber, which are temporarily in the MSC service area. Therefore, in praxis it is always associated with an MSC.
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The VLR request the subscriber profiles of sucscriber with activated MS/UE ithe MSC service area from the Home Location Register(HLR) and stores them temporarily. Temporarily means as long as the subscriber is not registered in a new MSC/VLR, even if he deactivated the MS/UE. Additional to the semi-permanent subscriber data received from the HLR, the VLR stores temporary data, e.g. information on the subscribers current location (the Location Area), the state of activation (Attached/Detached). Furthermore, the VLR is responsible for the initiation of security functions, e.g. the Authentication procedure, the start of ciphering and the TMSI re-allocation. Examples of subscriber data in the VLR: MSISDN: Mobile Subscriber ISDN No. IMSI: International Mobile Subscriber Identity TMSI: Temporary Mobile Subscriber Identity LMSI: Local Mobile Subscriber Identity MSRN: Mobile Station Roaming Number LAI: Location Area Identity zezenenu.und.lmm/ximemubi.en.slo
Authentication Parameter The identity of the SGSN where the MS has been registered
Fig. 12 Visitor Location Register
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2.2.2.6 Transcoding TC function The Transcoding TC function is used to perform conversion between standard ISDN 64 kbit/s speech transmission and the UMTS Adaptive Multi-Rate (AMR) speech codec (Specs: 26-series). The AMR speech coder is a single integrated speech codec with eight source rates from 4.75 kbit/s to 12.2 kbit/s, and a low rate background noise encoding mode. The speech coder is capable of switching its bit-rate every 20 ms speech frame upon command (TS 26.071). Different to GSM, in UMTS the Transcoding function is not part of the Radio Access Network RAN. It has been defined as part of the UMTS Core Network CN. Some optimization procedures allow it be passed through, without transcoding, in the case of UE to UE communication for example, when double-transcoding would be performed for nothing.
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2.2.2.7 Interworking Function The “classical” Core Network CN interface (e.g. A-G) are all Time Division Multiplexed TDM based (E1/T1). Different to this, the Iu interface between UTRAN and the UMTS CN is ATM-based. An Interworking Function (IWF) is necessary for conversion between TDM-based and ATM-based interfaces. Remark: IWF and TC function can be stand-alone network elements or be integrated into the UMTS MSC, depending on the manufacturers / network operators decision / demands.
Fig. 13 Transcoding and InterWorking Function
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2.2.3
Packet Switch Network Element
2.2.3.1 Serving GPRS Support Node The Serving GPRS Support Node (SGSN) constitutes an interface between the radio access network and the core network. It is responsible to perform all necessary functions to handle packet switched services to and from the mobile phone. SGSN performs following task: Network Access Control Authentication is one aspect of network access control. Hereby, the network is checking the validity of the subscriber’s USIM and the USIM is checking the validity of the network (SGSN). Only if both sides determine a successful authentication, network services can be used.
Mobility Management Similar to the MSC, the SGSN is responsible for the mobility management, which includes procedures like routing area update and paging. Packet Routing and Transfer Its tasks include the classical packet switching aspects, such as relaying, routing, address translation, encapsulation, and tunnelling. In contrast to the 2G-SGSN, a 3G-SGSN is not responsible for ciphering and user data compression.
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Then the subscriber is requesting a service, the Authorisation process makes sure, that the subscriber is allowed to use the requested service. The services, the subscriber is authorised to use may depend on his location. Other important tasks of network access control are the collection of Charging Data Records (CDR) and Operator Determined Barring.
UMTS Network Architecture
2.2.3.2 Gateway GPRS Support Node The Gateway GPRS Support Node (GGSN) constitutes the interface between the PLNM and external packet data networks (PDN). Similar to the SGSN, it is responsible for the PS service provisioning. GGSN performs following task: Network Access Control Two main network access control tasks are performed with a GGSN: It is responsible for screening, i.e. the operator can determine, which type of packets is allowed to be transmitted via a GGSN. Some manufacturers have outsourced this function into a separate firewall. The GGSN is also responsible for charging data generation. Mobility Management The mobility management tasks include HLR inquiries in case of a mobile terminated call. Packet Routing and Transfer
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Packets have to be routed. The GGSN is responsible to relay them from one link to another, determine the next route with the help of routing tables. The GTP protocol is used between the GGSN and SGSN/RNC. The user data is encapsulated to be transparently transmitted between the GGSN and RNC. This is called tunnelling.
2.2.3.3 Border Gateway Function Roaming is possible for packet switched services. Hereby, user data and signalling information is transmitted between the two PLMN via the interface Gp. The data has to pass Border Gateways (BG) in each PLMN. The BG interfaces the PLMN and external, inter-PLMN backbone networks. Based on the roaming agreement between two operators, border gateways can perform mutual authentication of each other before a secure connection is established between them and data flows pass via them. 2.2.3.4 Charging Gateway Function Both SGSN and GGSN generate Charging Data Records (CDR). The CDRs routed via the CGF to the billing system. The interface Ga is used between SGSN/GGSN and Charging Gateway Function (CGF). CGF is responsible to: Manage reliable CDRs Act as intermediate storage for CDRs Pre-processing of CDRs before forwarding them to the billing centre.
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3
The UMTS Release 4 Architecture
UMTS networks are designed to offer a wide range of multimedia services. A consequence of more variable services is that the core network must offer more efficient and flexible transport options than the Release 99 network does. Therefore the UMTS Core Network CS domain is a central aspect of Release 4 modification (TS 23.002). The intention of these modifications is a separation of the call control from the transport the user data. A wide range of bearers must be made available in the core and radio access network to make these new services available for the subscriber. Today’s exchanges and MSCs are optimized for voice transport. An MSC is responsible for:
With so many different tasks combined in one network element, any modification is costly and time consuming. With a traditional MSC it is very hard for operators to react fast to changing demand in the market. More flexible solutions are required. Beginning with UMTS Release 4, call control and bearer control and management are separated. The separation of planes is done in the UMTS Release 4 circuit switched domain. The UMTS Release 99 network elements MSC/VLR, and GMSC are substituted by the network entities MSC-Server, GMSC-Server and CS-MGW (Circuit Switched – Media Gateway).
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Bearer control and bearer management Call control Service provisioning
UMTS Network Architecture
Fig. 14 UMTS Core Network Release 4 CS Domain
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3.1
Circuit Switched – Media Gateway (CS-MGW)
The CS-MGW is responsible for bearer control. Its functions include: Bearer control: The requirements for the bearer control are set in the (G)-MSC-Server. The CS-MGW gets this information via an open interface. The CS-MGW must determine, whether it can make bearers available in accordance to the QoS parameters set. Bearer channel termination: The different transmission technologies may be in use, e.g. ATM and IP over Ethernet. The ATM bearer then ends in the MGW and the IP bearer begins at the MGW for user data transport.
Mobile specific functions: A CS-MGW must support mobility specific functions, such as SRNC relocation and handover procedures. The CS MGW can also be connected to other networks such as PSTN and PLMN using the following interfaces: A-interface : to the GSM Base Station Controller BSC Iu-CS interface: to the RNC Nb-interface: to other MGW. Different options are possible on Nb for user data transfer and bearer control signaling (e.g. ATM, IP).
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Media conversion and payload processing: If the CS-MGW is interfacing UTRAN, voice information must be processed. E.g. voice may be transmitted with 64 kbps in the core network, but for the radio interface, 12.2 kbps speech is required. The UMTS specific voice codec is found in the MGW. The same is true for conference bridges, echo cancellers, etc.
UMTS Network Architecture
3.2
Mobile Switching Centre Server
Mobile Switching Centre Server (MSC server) concept offers common core network for the GSM and the UMTS subscribers. Release 99 introduces the UTRAN network. NSN's 3G-MSC offers connections both towards the GSM Base Station Subsystem (BSS) and towards the WCDMA-based UMTS Terrestrial Radio Access Network (UTRAN). When the network architecture based on UMTS Release 4 is introduced, the user and control planes are separated in the network. This means that the 3G-MSC evolves to the direction where the MSC's switching functions are brought to the Media Gateway (MGW) product, and the MSC evolves to an MSS-like product. The MSS product provides call control logic for terminals that use circuit switched logic.
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MSS mainly comprises the call control and mobility control parts of a GSM/UMTS MSC. The MSS is responsible for the control of mobile originated and mobile terminated circuit switched calls. It terminates the user-network signalling and translates it into the relevant network – network signalling. The MSS also contains a VLR to hold the mobile subscribers' service data and CAMEL related data. MSS controls the parts of the call state that pertain to connection control for media channels in a MGW. The MSC server connects to the Media Gateway using the H.248 protocol (MEGACO). The physical connection between the MSC server and Media Gateway (MGW) is Ethernet. The interface between two MGWs performs bearer control and transport through the ATM backbone by using several ATM Adaptation Layer protocols (AAL1, AAL2, and AAL5) or the IP backbone. The functionality of the MSC server can be divided into two roles: Visited MSS (VMSS) and Gateway MSS. VMSS contains VLR and controls the MGW that is connected towards the (BSS and UTRAN) radio networks. Gateway MSS functionality is to control the MGW that is performing interworking between packet core network and the external PSTN/ISDN network. The NSN product that performs the Gateway MSS functionality is called Gateway Control Server (GCS).
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3.3
CAMEL Service Environment CSE
GSM Service Control Function (gsmSCF): functional entity that contains the CAMEL service logic to implement Operator-Specific Services OSS. It interfaces e.g. with the gsmSSF, the gprsSSF and the HLR. GSM Service Switching Function (gsmSSF): functional entity that interfaces the MSC/GMSC to the gsmSCF. The concept of the gsmSSF is derived from the IN SSF, but uses different triggering mechanisms because of the nature of the mobile network. GPRS Service Switching Function (gprsSSF): functional entity that interfaces the SGSN to the gsmSCF. Home Location Register HLR: for subscribers requiring CAMEL support, the HLR stores different types of CAMEL Subscriber Information CSI (e.g. O-CSI for Mobile Originating Calls, T-CSI for Mobile Terminating Calls). The O-CSI is sent to VLR at Location Update, on data restoration of if the O-CSI is updated by administrative action. The O/T-CSI is sent to the GMSC when the HLR responds to a request for routing information. MSC/VLR or SGSN: VLR or SGSN store the different CSI information as part of the subscriber data for subscribers roaming in the MSC/VLR or SGSN area. MSC or SGSN monitor the call states and communicate (internally) with gsmSSF for further proceeding.
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For the introduction of CAMEL services, some network elements have to be enhanced and new functional entities have to be introduced (TS 23.078):
UMTS Network Architecture
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Fig. 15 CAMEL Services
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4
The UMTS Release 5 Architecture
UMTS Release 5 CN In Release 5 the CS domain should be just an option. The so-called “All IP CN” is introduced using the PS domain and an additional IP Multimedia Subsystem(IMS). The IMS is interfaced to the PS domain like an external PDN, i.e. via Gi interface. For downward-compatibility reason to GSM and UMTS Release 99 and Release 4 it might be necessary, to support additionally the CS domain. In the following, the central new Release 5 network entities / functions are described:
Media Gateway MGW: The MGW ensures interoperability and interworking between an all IP CN and the external fixed CS networks PSTN or ISDN. The MGW enables conversion for CS data transmission, e.g. voice transmission, to PS data transmission, e.g. Voice over IP(VoIP). Echo cancellation via Gi interface toward the GGSNs. Call State Control Function CSCF: The CSCF is responsible for e.g. Session Flow Handing and Application Coordination. They are interfacing the IN/ Application Server/ IN and they are responsible to collect charging data CDRs.
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Home Subscriber Server (HSS): The HSS is used for mobility related aspects, very similar to the “classical” HLR (storing subscription and routing information).
UMTS Network Architecture
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Fig. 16 UMTS Release 5 CN
The UMTS Release 5 offers a wide range of improvements compared to earlier releases. Two of the main new features are the IP Multimedia Subsystem (IMS) and the radio network improvement High Speed Packet Access (HSPA). The reason why IMS is adopted by the MNO is the incredible grow-up of the application environment for Mobile users. IP-based application infrastructure is a mandatory in order to offer Multimedia applications for MNO's Today the multimedia application IP-based runs under several platforms and mostly not standard architectures. IMS provided a centralized platform and standardized architecture complaint to 3GPP standards. The IMS provides services for any types of IP-based communications whether they are video telephony, video on demand, an instant multimedia messaging, multimedia gaming or virtual-reality. Non-time critical/near -real-time applications & service such as: Presence services: i.e. presence enhanced buddy list or presence enhanced corporate directories. User configuration of presence and availability data Instant messaging Chat rooms
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Multimedia messaging (sending any combination of voice, voice and text clips) Non-real-time critical games Streaming of voice/video Push to talk or push to watch Real-time applications & services such as: Voice/Video over IP Voice and video conferencing Real-time critical games Integrated applications & services such as:
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Voice and games Click to call from buddy list, web page, etc Virtual reality applications and integrated calendar services
Fig. 17 IMS/SIP
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4.1
IMS Reference Architecture
The IMS Solution is based on two sets of standards: The 3rd Generation Partnership Project (3PP) Technical Specifications (TS) for the Release 5 and 6(R5, R6). These standards were driven by mobile network operators (MNO) and equipment vendors. The European Telecommunication Standard Institute (ETSI) Telecommunications and Internet Converged Services and Protocol for Advanced Networking (TISPAN) Next Generation Network (NGN) Release 1 standard. The focus of the ETST TISPAN NGN standard is to provide a standard for converged services from the fixed network operator’s (FNO) point of view. Due to the fact that IMS 5.0 is compliant with the 3GPP specifications R5 and R6, the 3GPP compliance of IMS 5.0 solution is assured. Because the 3GPP IMS was selected in the ETSI TISPAN NGN standards as the heart of the network, the IMS 5.0 solution is therefore also compliant with them.
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Fig. 18 Reference Standard
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4.2
IP Multimedia Subsystem
The objective of the IP Multimedia Subsystem (IMS) is to support applications involving multiple media components per session in such a way that the network is able to dissociate different flows with potentially different QoS characteristics associated to the multimedia session. These applications are called IP Multimedia applications. Examples of such applications are multimedia session offering the possibility to add and drop component(s) such as video, audio, end users, or tools as shared online whiteboards. The impact on the network is the creation of a set of new entities, the IMS, dedicated to the handling of the signaling and user traffic flows related to these applications. All IMS entities are located in the Core Network. The impact on non-IMS specific network entities is kept as low as possible.
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The fixed Internet multimedia call control Session Initiated Protocol (SIP) defined by IETF is chosen as IMS main protocol for its flexible syntax. SIP also allows for development of common applications and interconnectivity between 3G UMTS networks and fixed IP networks such as Internet.
Fig. 19 UMTS Release 5 IMS & PS Domain
To transport IMS signaling and user data, IMS entities use the bearer services provided by the PS domain and the UTRAN. With some exceptions, the PS domain and the UTRAN domain consider IMS signaling and IMS applications flows as user data flows, thus minimizing the impact on existing architecture on non-IMS entities. As part of the bearer services offered by the PS domain to the IMS, the PS domain supports the handover functionality for maintaining the service while the terminal changes the location.
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Fig. 20 IMS 5.0 Overview
The main entities of IMS are: zezenenu.und.lmm/ximemubi.en.slo
Proxy-Call State Control Function (P-CSCF): this is the first contact point of IMS.It is located in the same network as the GGSN (visited or home network, shown as being in the visited network in the figure). Its main task is to select the I-CSCF of the Home Network of the user. It also performs some local analysis e.g. number translation, QoS policing. Interrogating-CSCF (I-CSCF) is the main entry point of the home network: it selects with the help of Home Subscriber Server (HSS) the appropriate S-CSCF. Serving-CSCF (S-CSCF): performs the actual Session Control. This function handles the SIP requests, performs the appropriate actions e.g. requests the home and visited networks to establish the bearers. It also forwards the requests to the SCSCF/external IP network of other end user as applicable. The S-CSCF might be specialized for the provisioning of a set of service or even a single service. Home Subscriber Server Stores the IMS User Profiles including the User Identification, Addressing information (Public-/Private User IDs, IMSI, MSISDN, ...), Service Provisioning Information (Filter Criteria), User Mobility Information (S-CSCF address), Charging Information (Charging Collection Function (CCF) and Event Charging Function (ECF) address), Radius Parameters (GCID, IP-address, SGSN-ID) Provides support for User Authentication (AKA Authentication Vector) and Mobility Control.
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The HSS therefore retrieves information from the HLR and the SMS-C via a MAP interface. Provides Subscriber Self Administration (SSA) support
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Fig. 21 IMS Key Component
The IMS provides the benefits of: IP transport in the core network IP transport in UTRAN End to end IP services Simpler service integration due to simplified protocol stacks Easy integration and enabling of instant messaging, presence information and real time conversation services Note further information is available in 3GPP specifications: TS23.228 TS23.002
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4.3
High Speed Downlink Packet Access
UMTS was introduced to offer a wide range of different services. High data rates and high flexibility was required from the UMTS Release 99 radio interface solution. Nonetheless, the maximum data rate was limited to 2 Mbps. In terms of high data rate transmitssion via the radio interface, especially in the pico cell environments, competing technologies are arousing. The most prominent pico cell high data rate wireless solution is Wireless LAN (WLAN), such as IEEE 802.11a, IEEE 802.11b, and HyperLAN. Already in UMTS Release 5, a technical innovation was introduced on the WCDMA radio interface and its radio access network UTRAN to offer data rates of up to 10 Mbps to individual subscribers: High Speed Downlink Packet Access (HSDPA). HSDPA is protocol belonging to the High-Speed Packet Access (HSPA) family of protocols. Some important features of HSDPA are as follows:
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HSDPA is a third generation (3G) mobile telephony communications protocol. HSDPA provides high speed data transfer and capacity to UMTS based networks. Currently, networks where HSDPA is implemented support down-link speeds of 1.8, 3.6, 7.2 and 14.4 Mbit/s. HSDPA was designed to offer high data rates for non-real time services. Only for downlink, high data rates were enabled, to support services such as fast file download, video streaming, and web-browsing. A set of features are in use with HSDPA to improve the transmission on the radio interface, such as Adaptive Modulation and Coding (AMC) Multiple Input Multiple Output (MIMO) Antenna Processiong Hybrid Automatic Repeat Request (HARQ) These techniques were already applied in other mobile communication systems. For instance, AMC and HARQ are used in EDGE. HSDPA is an enhancement of an existing, UMTS Release 99 solution: the Downlink Share Channel: DSCH. As the name "downlink shared channel" already indicates, several subscribers share the radio interface resource.
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4.3.1
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Fig. 22 HSDPA
Hybrid automatic repeat-request (HARQ)
HARQ transmits user data multiple times using different codings. This process is also called Incremental Redundancy. To recover the error-free packet efficiently, the user device saves the corrupted packet when received and then combines it with the retransmissions. This combination yields an error-free packet, even if the retramsmitted packets are corrupted.
4.3.2
Fast packet scheduling
The available radio conditions can be best used by sharing the HS-DSCH downlink channel between the users. The signal quality of the downlink is indicated in a periodic transmission, upto 500 times per second, by each user device. This information is used by the base station to identify which users need to be sent data in the next 2ms frame and the amount of data to be sent for each user. The users transmitting high downlink signal quality can be sent more data.
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The network determines the amount of the channelisation code tree and thereby, determines the network bandwidth allocated to the HSDPA users. This allocation of code tree is semi-static, which means it can be modified while the network is operating, but not on a frame-by-frame basis. This allocation of code tree represents a swapping of the bandwidth allocated for HSDPA users and bandwidth allocated for voice and non-HSDPA data users. For allocation of the code tree, units of channelisation codes for Spreading Factor 16 is used, which means that 16 units exist and units up to 15 can be allocated to HSDPA. The base station decides which channelisation codes will be used while deciding the users who will receive data on the next frame. This channelisation code information is sent to the user devices over the HSDPA scheduling channels. As discussed earlier, these scheduling channels are allocated separately and not included in the HSDPA allocation. As a result, for a 2ms frame, data is sent to many users at the same time using different channelisation codes. The number of allocated channelisation codes determine the maximum number of users that will receive data on a given 2 ms frame.
4.3.3
Adaptive modulation and coding
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The modulation scheme and coding is changed on a per-user basis depending on signal quality and cell usage. The initial scheme is Quadrature phase-shift keying (QPSK), but in good radio conditions 16QAM modulation almost doubles data throughput rates. With 5 Code allocation, QPSK typically offers up to 1.8 Mbit/s peak data rates, while 16QAM up to 3.6. Additional codes (e.g. 10, 15) can also be used to improve these data rates or extend the network capacity throughput significantly. Theoretically, HSDPA can give throughput up to 14.4 Mbit/s. Other Improvements HSDPA is included in the UMTS standards since Release 5. This release also includes an improvement for providing an uplink carrier of 384 kbit/s, which was 128 kbits/s in previous releases. In addition to increased data rates, HSDPA has also increased latency and as a result, the round trip time for applications is improved. Three new physical channels are included for data transmission in addition to the HS-DSCH channel. These three channels are: High Speed-Shared Control Channel (HS-SCCH), High Speed-Dedicated Physical Control Channel (HS-DPCCH) and High Speed-Physical Downlink Shared Channel (HS-PDSCH). HS-SCCH informs the user that data will be sent on the HS-DSCH 2 slots. HS-DPCCH acknowledges the received information and includes the current channel quality indicator (CQI) of the user. Next, the CQI value is used by the base station to calculate the data to be sent to the user devices during the next round of transmission. HS-PDSCH is mapped to the HS-DSCH transport channel, which carries the actual user data.
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4.4
The UMTS Evolution in Release 5
The UMTS Release 5 specifies additional features in UTRAN Architecture to enhance previous UMTS releases. The most significant enhancements to the UTRAN architecture introduced in Release 5 are described as the following sections.
4.4.1
IP Transport in UTRAN
In previous releases, Release 99 and Release 4, ATM is solely used at the transport layer in the various interfaces. The IP Transport in UTRAN feature is provided to use IP at the transport layer in Iub, Iur, Iu-Ps and Iu-Cs interfaces as an alternative to ATM.
4.4.2
Intra Domain Connection of RAN Nodes to Multiple CN Nodes (Iu Flex)
This feature introduces the capability to connect one RNC to more than one MSC and to more than one SGSN. The main benefits of the Iu Flex (abbreviation from the word “flexible”) are to provide load sharing between MSCs and between SGSNs to improve the efficiency of hardware utilization further, and to increase the possibility to anchor the MSC and SGSN in case of SRNS relocation.
4.4.3
Standalone Serving Mobile Location Centre (SAS) and SMLC-SRNC Interface (Iu-pc)
Since location-based services are expected to be one of key services for 3G mobile operators, UTRAN architecture includes a network element which is called “Standalone Serving Mobile Location Centre (Standalone SMLC or SAS)” for handling positioning measurements of mobile stations. In addition to the SAS, the interface between SAS and the SRNC, Iu-pc, is specified as an open interface. The Iupc interface is used to forward UE Positioning assistance information to UEs and to receive UE Positioning measurement data from the RNC. The SAS and Iupc interface are optional elements, since SMLC functionality can be integrated in the RNC.
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In accordance with this alternative feature, protocols to transport Radio and Signaling bearers can be carried over IP with different solutions: the user plane UDP/IP protocols are used on Iub/Iur and RTP/UDP/IP protocols are used on Iu-Cs for user plane, and SCTP protocol is used for the Iub control plane.
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4.4.4
GERAN/UTRAN Interface Evolution and the Iur-g Interface
GERAN/UTRAN Interface Evolution allows the GSM/EDGE Ratio Access Network (GERAN) to connect to Core Network through different interfaces, A, Gb, Iu-cs and Iu-ps. The GERAN/UTRAN Interface Evolution work item provides the requirements on Iu-cs and Iu-ps from GERAN perspective and requires some modification on both interfaces to cover GERAN specific issues. The Iur-g interface is the logical interface between two BSSs or a BSC and an RNC. It provides capability to support radio interface mobility between BSSs or between a BSS and an RNS of UEs having a connection with the GERAN or the UTRAN. This capability includes the support of paging, cell update, registration area update and handover between BSSs or between a BSS and a RNS. Furthermore, the Iur-g interface allows information exchange between two BSSs or between a BSS and RNS.
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5
The UMTS Release 6 Overview
Release 6 is an enhancement of earlier 3GPP releases, aiming to bring mobile users a complete 3G experience. 3GPP Release 6 includes numerous new features, among them being High Speed Uplink Packet Access (HSUPA), the second phase of IP Multimedia Subsystem (IMS), inter-working with Wireless Local Area Networks (WLAN), Multimedia Broadcast Multicast Service (MBMS), and Enablers for Push to Talk.
The second phase of IMS comprises all the core network elements for offering multimedia services. IMS makes it possible for operators to offer mobile users multimedia services using Session Initiation Protocol (SIP). SIP enables mobile users to use services based on Internet applications. In Release 6, IMS is developed to support inter-working with circuit-switched networks, non-IMS networks and 3GPP2 based CDMA systems. Release 6 also defines inter-working with Wireless Local Area Networks (WLANs). The inter-working is defined in a very flexible way, enabling different multi-radio scenarios. Multimedia Broadcast Multicast Service (MBMS) makes it possible to efficiently distribute multimedia content to multiple recipients. Such content could be for example video or music clips. Conversational services such as Push to talk are also specified in Release 6, together with the Open Mobile Alliance (OMA).
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High Speed Uplink Packet Access (E-DCH or HSUPA) will complement the High Speed Downlink Packet Access (HSDPA) for a rich, two-way, interactive wireless broadband user experience. HSUPA and HSDPA together will enable symmetrical data communications at a high speed, supporting multimedia, Voice over IP etc.
UMTS Network Architecture
Fig. 23 UMTS Release 6 Features
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Fig. 24 UMTS Rel 6: IMS Services
5.1
Multimedia Broadcast Multicast Service
One key feature targeted for 3GPP Rel’6 is the Multimedia Broadcast Multicast Service (MBMS) feature, which defines capabilities to address the same information to many users in one cell using the same radio resources. The MBMS is a unidirectional point-to-multipoint service in which data is transmitted from a single source entity to multiple recipients. Transmitting the same data to multiple recipients allows network resources to be shared. By this, the MBMS architecture enables the efficient usage of radio network and core-network resources, with an emphasis on radio interface efficiency. MBMS is provided over a broadcast or multicast service area which can cover the whole network or be a small geographical area such as a shopping mall or sports stadium allowing for region
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specific content distribution.
Fig. 25 Multimedia Broadcast Multicast Service
5.2
WLAN Interworking
WLAN operated either by 3GPP operator or by 3rd party. 6 scenarios are defined as the following: Scenario 1: Common billing and customer care (Receive only one bill) Scenario 2: Common access control (authentication and authorisation) using a (U)SIM based solution and charging Scenario 3: Access to all 3GPP packet-switched services (e.g., IMS, Push etc.) and services like SMS or MMS Scenario 4: Service continuity between different accesses like WLAN and UTRAN (i.e.service must not be set-up again, if access technology is changed) Scenario 5: Seamless mobility between WLAN and 3GPP access networks Scenario 6: Seamless handover even for CS services In Rel6, only scenarios 1-3 are supported
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Fig. 26 WLAN Interworking
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Fig. 27 WLAN Interworking
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6
Long Term Evolution
3GPP works on the Evolution of the 3G Mobile System started with the RAN Evolution Work Shop, 2-3 November 2004 in Toronto, Canada. The Work shop was open to all interested organizations, members and non members of 3GPP. Operators, manufacturers and research institutes presented more than 40 contributions with view and proposals on the evolution of the Universal Terrestrial Radio Access Network (UTRAN). A Set of high level requirement was identified in the Work Shop: Reduce cost per bit Increased service provisioning – more services at lower cost with better user experience Flexibility of use existing and new frequency bands Simplified architecture, Open interfaces
It was also recommended that the Evolved UTRAN should bring significant improvements to justify the standardization effort and it should avoid unnecessary options. On certain aspects, the collaboration with 3GPP SA WGs was found to be essential: the new split between the Access Network and the Core Network, and the characteristics of the throughput that new services would require demanded close architecture coordination. With the conclusion of this Work Shop and with broad support from 3GPP members, a feasibility study on the UTRA & UTRAN Long Term Evolution (LTE) was started in December 2004. The objective was “to develop a frame work for the evolution of the 3GPP radio-access technology toward a high-data-rate, low-latency and packet-optimized radio-access technology”. The study focused on supporting services provided from the PS domain, involving: Related to the radio-interface physical layer (downlink and uplink):e.g. means to support flexible transmission bandwidth up to 20 MHz, introduction of new transmission schemes and advanced multi-antenna technologies. Related to the radio interface layer 2 and 3:e.g. signaling optimization Related to the UTRAN architecture: e.g. identify the optimum UTRAN network architecture and functional split between RAN network nodes.
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Allow for reasonable terminal power consumption
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In addition, the Next Generation Mobile Networks (NGMN) initiative, led by seven network operators provided a set of recommendations for the creation of networks suitable for the competitive delivery of mobile broadband services. The NGMN goal is “to provide a coherent vision for technology evolution beyond 3G for the competitive delivery of broadband wireless services”. The NGMN long-term objective is “to establish clear performance targets, fundamental recommendations and deployment scenarios for a future wide area mobile broadband network”. In a white paper (March 2006), they provided relative priorities of key system characteristics, System recommendations and detailed requirements.
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Fig. 28 Macro-Level Network Architecture in 2012
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6.1
System Architecture Evolution
SA WG2 started its own Study for the System Architecture Evolution (SAE) whose objective is “to develop a framework for an evolution or migration of the 3GPP system to a higher-data-rate, lower-latency, packet-optimized system that supports, multiple RATs. The focus of this work is on the PS domain with the assumption that voice services are supported in this domain”. SA2’s SAE work is conducted under Work Item “3GPP system architectural evolution”, approved in December 2004. It was initiated when it became clear that the future was clearly IP with everything (the “All-IP” network, AIPN –see TS 22.978), and that access to the 3GPP network would ultimately be not only via UTRAN or GERAN but by WiFi, WiMAX, or even wired technologies. Thus SAE has as its main objectives: Impact on overall architecture resulting from RAN’s LTE work. Impact on overall architecture resulting from SA1’s AIPN work. Overall architecture aspects resulting from the need to support mobility between heterogeneous access networks.
New reference points have been defined: S1: It provides access to Evolved RAN radio resources for the transport of user plane and control plane traffic. The S1 reference point shall enable MME and UPE separation and also deployments of a combined MME and UPE solution. S2a: It provides the user plane with related control and mobility support between a trusted on 3GPP IP access and the SAE Anchor. S2b: It provides the user plane with related control and mobility support between ePDG and the SAE Anchor. S3: It enables user and bearer information exchange for inter 3GPP access system mobility in idle and/or active state. It is based on Gn reference point as defined between SGSNs.User data forwarding for inter 3GPP access system mobility in active state (FFS). S4: It provides the user plane with related control and mobility support between GPRS Core and the 3GPP Anchor and is based on Gn reference point as defined between SGSN and GGSN. S5a: It provides the user plane with related control and mobility support between MME/UPE and 3GPP anchor. It is FFS whether a standardized S5a exists or whether MME/UPE and 3GPP anchor are combined into one entity. S5b: It provides the user plane with related control and mobility support between 3GPP anchor and SAE anchor. It is FFS whether a standardized S5b exists or whether 3GPP anchor and SAE anchor are combined into one entity.
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The figure below shows the evolved system architecture, possibly relying on different access technologies.
UMTS Network Architecture
S6: It enables transfer of subscription and authentication data for authenticating/authorizing user access to the evolved system (AAA interface). S7: It provided transfer of QoS policy and charging rules from Policy and Charging Rule Function (PCRF) to Policy and Charging Enforcement Point(PCEP). The allocation of the PCEP is FFS. SGi: It is the reference point between the Inter AS Anchor and the packet data network. Packet data network may be an operator external public or private packet data network or an intra operator packet data network, e.g. for provision of IMS services. This reference point corresponds to Gi and Wi functionalities and supports any 3GPP and non-3GPP access systems. The interface between the SGSN in 2G/3G Core Network and Evolved Packet Core (EPC) will be based on the GTP protocol. The interface between the SAE MME/UPE and the 2G/3G Core Network will be based on the GTP protocol.
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Fig. 29 LTE System Architecture Evolution
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7
Appendix
Note: This appendix is mainly provided for self-study. In UMTS Release 99, the main focus lay on the access part of the network, UTRAN, and the WCDMA solution for UMTS. On the core network side, the aim was to minimise changes and utilise the existing GSM/GPRS network elements and functions as much as possible. In 2000, the 3GPP wanted to introduce a new core network solution. It is generally referred to as “All IP CN” solution. Due to the huge amount of problems in the specification process, new core network features, but also new radio access network features were – and will be – introduced from the year 2001 onward in annul releases. The first release following UMTS Release 99 was UMTS Release 4. It was frozen in March 2001. Among other things, following aspects were specified: • Low chip rate TDD mode (a 1.6 MHz TDD mode for Asia) • UTRA repeater • Node B synchronization zezenenu.und.lmm/ximemubi.en.slo
• Transcoder free operation • QoS architecture for PS-domain • Bearer independent circuit switched core network architecture • Multimedia Messaging Service • MExE, OSA, and LCS enhancements. The core network evolution was especially affected by the “bearer independent CS core network architecture”. Its concept is outlined below.
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8
Exercises
Exercise 1 Which of the following elements are not part of the UMTS network? HLR/AC MSC EIR BSC OMC SMS-SC GGSN zezenenu.und.lmm/ximemubi.en.slo
Exercise 2 What are the main tasks of a 3G MSC? (Choose two) Switching of CS traffic Call Setup & Release Storing the User Equipments location Charging Generating Security Paramter
Exercise 3 Which of the following information is not kept on the SIM? IMSI number SMS messages Network information (that is, location area) Time and date
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Exercise 4 Which of the following alternatives include radio access specifications (Choose three)? GSM IP EDGE UTRAN
Exercise 5 Which of the following alternatives are NOT functions of the base station? (Choose two)
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Speech coding Transmission of signal Modulation Charging data generation
Exercise 6 Batteries are used at a site as an alternative source of energy for the BTS in case of a power failure. TRUE FALSE
Exercise 7 If we say that the BTS is a 2+2+2, what does it mean? There are 3 locations where we can find 2 sites. A single site is divided into 3 cells, each with 2 TRXs/carriers. A single site is divided into 2 cells, each with 3 TRXs/carriers.
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A TRX/carrier is divided into 3 time slots
Exercise 8 The Iur interface is used between two RNCs. What is the purpose of this interface? There is no use for this interface. It is used for soft handovers. It is used to transfer software files. It is used when a RNC has a hardware failure.
Exercise 9 Which of the following network elements is not part of UTRAN? RNC zezenenu.und.lmm/ximemubi.en.slo
Node B IWF VLR
Exercise 10 Which of the following is a new Release 4 element? Media Gateway Home Location Register Gateway GPRS Support Node Base Transceiver Station
Exercise 11 Which of the following sentences are NOT true? MGW for 3G-MSC contains the transcoding function.
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Uplink peak data rates of HSPDA can be as high as 14 Kbps. The existing MSC, HLR will support 3G by SW upgrade. GGSN will be compatible to both 2G and 3G-GPRS network elements by minor SW and HW upgrade.
Exercise 12 Which of the following network elements are new in Release 5? Media Gateway MGW Media Gateway Control Function MGCF Call State Control Function CSCF MSC Server
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Home Subscriber Server HSS
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8.1
Solutions
Exercise 1 (Solution) Which of the following elements are not part of the UMTS network? HLR/AC MSC EIR BSC OMC SMS-SC GGSN zezenenu.und.lmm/ximemubi.en.slo
Exercise 2 (Solution) What are the main tasks of a 3G MSC? (Choose two) Switching of CS traffic Call Setup & Release Storing the User Equipments location Charging Generating Security Paramter
Exercise 3 (Solution) Which of the following information is not kept on the SIM? IMSI number SMS messages Network information (that is, location area) Time and date
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Exercise 4 (Solution) Which of the following alternatives include radio access specifications (Choose three)? GSM IP EDGE UTRAN
Exercise 5 (Solution) Which of the following alternatives are NOT functions of the base station? (Choose two)
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Speech coding Transmission of signal Modulation Charging data generation
Exercise 6 (Solution) Batteries are used at a site as an alternative source of energy for the BTS in case of a power failure. TRUE FALSE
Exercise 7 (Solution) If we say that the BTS is a 2+2+2, what does it mean? There are 3 locations where we can find 2 sites. A single site is divided into 3 cells, each with 2 TRXs/carriers. A single site is divided into 2 cells, each with 3 TRXs/carriers.
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A TRX/carrier is divided into 3 time slots
Exercise 8 (Solution) The Iur interface is used between two RNCs. What is the purpose of this interface? There is no use for this interface. It is used for soft handovers. It is used to transfer software files. It is used when a RNC has a hardware failure.
Exercise 9 (Solution) Which of the following network elements is not part of UTRAN? RNC zezenenu.und.lmm/ximemubi.en.slo
Node B IWF VLR
Exercise 10 (Solution) Which of the following is a new Release 4 element? Media Gateway Home Location Register Gateway GPRS Support Node Base Transceiver Station
Exercise 11 (Solution) Which of the following sentences are NOT true? MGW for 3G-MSC contains the transcoding function.
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Uplink peak data rates of HSPDA can be as high as 14 Kbps. The existing MSC, HLR will support 3G by SW upgrade. GGSN will be compatible to both 2G and 3G-GPRS network elements by minor SW and HW upgrade.
Exercise 12 (Solution) Which of the following network elements are new in Release 5? Media Gateway MGW Media Gateway Control Function MGCF Call State Control Function CSCF MSC Server
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Home Subscriber Server HSS
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Principles of UMTS Terrestrial Radio Access (UTRA)
Principles of UMTS Terrestrial Radio Access (UTRA)
Contents zezenenu.und.lmm/cajaqara.en.slo
1
Module Objectives.....................................................................................4
2 2.1 2.2 2.3 2.4 2.5
Understand The Terms Carrier, Spreading And Power Density In UMTS ........................................................................................5 Multiple Access Method.............................................................................. 5 WCDMA - Basic Theory..............................................................................9 Overview of the UMTS Air Interface (Uu)................................................. 13 Modulation.................................................................................................16 The WCDMA Carrier................................................................................. 19
3 3.1 3.2
Principles of Radio Duplex.....................................................................20 UMTS Frame Structure............................................................................. 20 Duplex Transmission: FDD and TDD ....................................................... 20
4 4.1 4.2 4.3 4.4 4.5 4.6 4.7 4.8
The Structure of the UMTS Air Interface.............................................. 24 CDMA Sequencing – A Way to Spread Information .................................24 Codes - What and why? ........................................................................... 26 Rate Matching........................................................................................... 29 Spreading Factor .......................................................................................33 Scrambling Code .......................................................................................34 Channelization Code .................................................................................35 Receiving Signals at the Terminal............................................................ 36 Channel Coding.........................................................................................39
5 5.1 5.2 5.3
UMTS Channel Structure........................................................................41 Logical Channels.......................................................................................41 Transport Channels...................................................................................41 Physical Channel .......................................................................................42
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5.5 6 6.1 6.2 7 7.1 7.2 7.3 7.4 7.5 7.6 7.7 7.8 7.9 7.10 8 8.1 8.2 9
3-2
Description of the UMTS-FDD Logical and Transport Channels................................................................................................... 44 UMTS-FDD Transport to Physical Channels............................................ 46 The Key Functions and tasks in Radio Resource Management.............................................................................................48 Overview of Radio Resource Management Functions ............................. 48 Radio Resource Control States ................................................................ 51 List the Roles of Radio Resource Management on Network.................................................................................................... 55 Admission Control..................................................................................... 55 Planning Uplink Admission Control........................................................... 57 Code Allocation .........................................................................................58 Channelisation Code Allocation, and Handovers..................................... 59 Scrambling Code Planning........................................................................60 Power Control............................................................................................61 Packet Scheduler...................................................................................... 63 Handover Control and Macro Diversity..................................................... 64 Handover Decision-Making Mechanism....................................................75 Load Control in the RNC ...........................................................................76 Multi Carrier CDMA / UTRA / Time Division Synchronous CDMA ................................................................................80 MC-CDMA and UTRA ............................................................................... 80 Time Division - Synchronous CDMA / Low Chip Rate Time Division Duplex Mode................................................................................82
9.1 9.2
High Speed Downlink Packet Access and High Speed Uplink Packet Access.............................................................................84 Introduction to High Speed Downlink Packet Access............................... 84 Introduction to High Speed Uplink Packet Access................................... 90
10 10.1
Appendix.................................................................................................. 94 UMTS radio network planning...................................................................94
11 11.1
Exercises..................................................................................................97 Solutions..................................................................................................103
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5.4
Principles of UMTS Terrestrial Radio Access (UTRA)
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1
Module Objectives
The objective of this module is to give the participant the introductory knowledge needed for explaining UMTS radio and transmission path. The topics to be covered include identifying the concepts of the radio path and basic WCDMA terminology. It also covers how the UMTS functions and the radio resources managed. After completing this module, the participants should be able to: Identify Radio Path Basics, WCDMA Basic Theory, and Spreading. Identify Power, Frequency Division Duplex, Time Division Duplex, and Cell Characteristics. Identify Scrambling Code and Channelisation Code. Identify the Structure of the UMTS air Interface, Modulation, Transport, Physical and Logical channels. Identify the Functions and Tasks in Radio Resource Management like Admission Control, Power Control, and Handover.
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Explain the High Speed Downlink Packet Access and High Speed Uplink Packet Access.
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2
Understand The Terms Carrier, Spreading And Power Density In UMTS
2.1
Multiple Access Method
A mobile system uses air connection in the radio spectrum to facilitate communication. Unlike a traditional fixed telephone system, it does not have a fixed link between the terminal and the network. When a subscriber makes a call or when he need to radio signal information from a terminal, a temporary connection is made through the air between the terminal and the mobile network. As mobile systems have developed, different radio transmission techniques were devised to facilitate air connection through the radio spectrum. These techniques aimed to enable maximum users to share the same space in the radio spectrum. At the same time, they aimed to ensure quality, coverage, and security of communication between the users. zezenenu.und.lmm/cajaqara.en.slo
The first generation of the mobile systems used the Frequency Division Multiple Access (FDMA) technique. In this technique, the radio spectrum is divided into a fixed number of channels on different frequencies and of a fixed bandwidth. Figure 1 shows the division of the radio spectrum in the case of FDMA:
Fig. 1 Radio Spectrum Division in FDMA
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In an FDMA mobile system, if a subscriber wants to make a call, the mobile system allocates the mobile a channel at a particular frequency. During this period, the subscriber is the sole user of the channel. After the call is complete, the channel is released and given to the next subscriber wishing to make a call. As systems evolved from analogue to digital, the same frequency could be shared by many users. This lead to the evolution of 2G mobile systems that used the Time Division Multiple Access (TDMA) technique. In a TDMA mobile system, each channel at a particular frequency is divided into timeslots. As a result, multiple subscribers can use the same frequency to communicate.
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Figure 2 describes the division of the radio spectrum in the case of TDMA:
Fig. 2 Radio Spectrum Division in TDMA
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Apart from TDMA, some 2G mobile systems also use another technique called Code Division Multiple Access (CDMA). In CDMA, the subscribers share the same frequency and time, but are separated by codes. CDMA technique evolved into a 3G technique known as Wideband CDMA (WCDMA). In WCDMA, the radio spectrum is split into channels. Each channel carries several users of variable size, separated by a code. CDMA can be compared to a room with people speaking different languages. Let us imagine that a corporate CEO is hosting a large multinational gathering. Our host, having mastered many languages, is primarily the one making the conversation. Our host demands that his guests speak in their native tongues. Our host, a true mediator, is able to interpret the conversations between guests if they wish to talk with each other; he can fluently follow several conversations at the same time. He can understand different speakers, all talking at the same time, because they speak in different languages. He occasionally has to tell some guests, who tend to get carried away, to speak a little softer; and he has to ask the soft speakers to talk more loudly so that he can hear them better.
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The party starts to mature and many more guests arrive. The overall volume begins to rise, because there are more people speaking at the same time. The host asks the guests nearest to him to speak more softly, while he asks the ones further away to please speak up.
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Fig. 3 The party hosted by a CEO is used explain the CDMA
CDMA functions are much like our party. The CEO hosting the party is our Base Station (BS) and the guests are the Mobile Stations (MS). The different languages correspond to codes in a CDMA system. The BS can tell the mobiles apart, even though they are transmitting at the same time, by the codes that they use. Figure 4 illustrates in CDMA how channels occur in the same frequency and time:
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Figure 3 illustrates the CEO theory of CDMA:
Principles of UMTS Terrestrial Radio Access (UTRA)
Fig. 4 CDMA Technique
The number of subscribers who share the same frequency are limited by the number of codes, and also by the amount of interference in the region of coverage called a cell. Also, the subscriber may use variable bit rates to transfer data. Such subscribers need more frequency to transfer data. zezenenu.und.lmm/cajaqara.en.slo
Technically, each subscriber in WCDMA or channel, as this includes signaling is separated by a code. When a mobile terminal is listening to many base stations, it can detect between them, since each cell has its own unique code. Similarly, when a base station is listening to mobile stations, it can detect different subscribers (channels) through a unique code. In WCDMA, the spectrum is split into channels. Each channel carries several users of variable size, separated by a code. You will next learn about the theory behind the WCDMA technique in detail. The number of users able to share the same space is limited by the number of codes, and also by the amount of interference in the cell ( region of coverage). Also, the user may have variable bit rates. This means that some users need more space to transfer information quicker than others do.
2.2
WCDMA - Basic Theory
The theory behind WCDMA can be made easier by understanding the relationship between the frequency, power, and spreading (≈transmission time of one bit/symbol). Assume that a base station needs to send a block of data to a mobile. This block of data could be in any form, such as speech, video, packet data or signalling. For the purpose of this discussion, you can assume the data to be of a fixed volume (not size). The amount of the power needed to transmit this block of data can be reduced by spreading it along a wide frequency band. To understand this, consider the analogy of spreading topping on a cake. By using a knife, the topping is spread to cover the whole surface area of the cake. The bigger the
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surface of the cake, the better you are able to spread the topping. By spreading data more over the frequency bandwidth, the power required to transmit data is reduced. This enables mobile systems to allow more subscribers to share the same frequency bandwidth. Compare this to a big room with a lot of people. If everybody would whisper, indicating lower power requirement, more people would be able to maintain the conversation. If, on the other hand, people would talk loud, indicating higher power requirement, less number of people would be able to maintain their conversation due to the interference from difference conversations. In WCDMA, the frequency bandwidth is fixed between 4.4 - 5 MHz by specifications. However, the power and the spreading factor are variable. The spreading factor indicates the degree to which the data can be spread over the fixed frequency band.
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Figure 5 explains the relationship between frequency, power, and spreading factor:
Fig. 5 Relationship between Frequency, Power, and Spreading Factor
Considering figure 5, assume that the block is a variable; Its volume is constant, only the sizes of the edges change. Therefore, you can calculate the volume as follows: Volume of block = L X B X H Here, length is the frequency band which is constant for WCDMA as 5 MHz breadth is the spreading factor and height is the power. The volume of the block is constant before and after transmission of the data. For example, if it is 100 before transmission it has be 100 after receiving the data. Therefore, you can conclude: 100 = 5 X B X H
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Since length, which is the frequency band is constant; either spreading factor or the power can vary. If spreading factor is low, then the power is high. Similarly, if the power is low, then the spreading factor is high. The spreading factor and hence the power depend on the bit rate of the data. The spreading factor is high for data with lower bit rate and low for data with high bit rate. Therefore, the power and spreading factor will be different for a video call that has a high bit rate with only small delays allowed as compared to Internet access that has lower bit rate with comparatively longer delays acceptable. Therefore, each subscriber has a different needs, depending on which service she/he uses. In addition, each subscriber needs minimal interference from other subscribers.
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Figure 6 shows how the needs of the subscribers are achieved by applying different codes:
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Fig. 6 Variable 'Slices' Allocated to Users
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2.3
Overview of the UMTS Air Interface (Uu)
Figure 7 illustrates the process of preparing data and signaling for the UMTS Air Interface:
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Fig. 7 Preparing the Data and Signaling for the UMTS Air Interface
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Table 1 describes the process of preparing data and signaling for the UMTS Air Interface: 1. Data and signaling are made ready for transmission by the terminal. The terminal is a platform with different applications, such as video, voice, and Internet access, running on it. These applications serve the data to be transmitted over a mobile system’s network. Apart from application data that is transmitted from the terminal over the network, the network must also exchange signaling messages with the terminals in order to control the activities of the terminal, such as instance location and connection management. 2. The signaling and data are fed through the network on logical channels. Different channels are used for different purposes. The content of the logical channels is mapped into physical channels with the help of transport channels. In the air interface, different physical channels are used to carry different kind of information. Also, channel coding is performed to support error correction.
4. The process of modulation, in which the coded data is converted from digital to analogue, is applied to the data and signaling. The data is transmitted over the air interface. 5. The receiving signal is reconstructed by the terminal and base station by collecting the circulating radio waves, reapplying the codes, and removing the error-correction coding. The receiver used in WCDMA is called the RAKE receiver (RAKE = collect). Table 1 the process of preparing data and signaling for the UMTS Air Interface
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3. As part of the coding process in WCDMA, the data is spread along the spectrum, and combined with a channelisation code, which is used to determine different physical channels and a unique scrambling code.
Principles of UMTS Terrestrial Radio Access (UTRA)
Steps when transmitting data or signalling from a User Equipment: The data is in a format that can be used by an application. The data is fed from a logical channel, via a transport channel onto a physical channel. The data in the physical channel is spread along the spectrum with a channelisation code, and combined with a scrambling code. Finally, the data is modulated onto the air interface. When subscriber data is received at Base Transceiver Station (BTS), follwoing three steps are performed at BTS: 1.
2.
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De-modulation is done (analogue to digital conversion). Also, the RAKE receiver contributes to a reception with less bit errors by enabling the summing up of signals that have taken different paths in the air interface (micro diversity). By using the same scrambling and channelisation codes as on the transmitting side, the receiving part is able to reconstruct the physical channel information. The channel coding is removed, and the data is forwarded towards the correct destination network (packet or circuit switched core network) on the appropriate logical channel.
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2.4
Modulation
To transmit the data or signaling information, the user data and signaling information are manipulated, for example, by adding redundancy and applying interleaving. Then, the coded data is ready for transmission as a radio wave.
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Figure 8 describes method to convert the coded data to an analog radio wave, modulation is applied to the coded data as highlighted:
Fig. 8 Modulation of Coded Data For Transmission
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Modulation is the process to transform binary data into an analogue signal at a certain frequency that corresponds with the carrier bandwidth. There are several different types of modulation methods. In GSM, Gaussian Minimum Shift Keying (GMSK) modulation method is used. In Enhanced Data Rates for Global Evolution (EDGE) both GMSK and 8 Phase Shift Keying (8-PSK) modulation methods can be used. In UMTS, the Quadrature Phase Shift Keying (QPSK) modulation method is used. The common feature among along the modulation methods is that they have predefined shapes for bit changes. However, each method shifts a different number of bits at a time. For example, GMSK shifts one bit at the time, QPSK shifts two bits at the time, and 8-PSK shifts three bits at a time. Figure 9 shows the basic idea with QPSK modulation, which is used in WCDMA:
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Fig. 9 Modulation with QPSK
The chips are hence modulated into a signal, which is to be transmitted on the air interface. The name QPSK means that there are four possible phase shifts. As the phase of the signal changes angle, this results in a 00, 10, 00, 01 signal. The receiver is able to reconstruct the signal by monitoring the changes in phase.
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QPSK is as such used for downlink. For uplink, a smooth and somewhat dirty variation of the QPSK method, called Offset QPSK (OQPSK), is applied. If a signal changes in QPSK, the transmitter changes directly to one of the four possible phases. When OQPSK is applied, the change from on phase to the next is done with intermediate steps. This reduces the requirements in the transmitter equipment, which makes it lighter and less expensive, as is required for the MS. The Release 5 feature High Speed Downlink Packet Access (HSDPA) is a packet-based data service in WCDMA downlink with higher data transmission rates. In good conditions up to 8-10 Mbps in downlink is possible. Data users close to the Node-B can be assigned higher order modulation with higher code rates, such as 16 Quadrature Amplitude Modulation (QAM).
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The Figure 10 describes how channelisation codes and scrambling codes, are used in WCDMA:
Fig. 10 Channelisation codes and scrambling codes
There are several related concepts that need further attention, such as chip, symbol, and spreading factor. First of all, however, we will define our physical resource for air interface transmission, the WCDMA carrier.
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2.5
The WCDMA Carrier
There are several bandwidths defined for the WCDMA, such as 5, 10, and 20 MHz. Nowadays, the 5 MHz is the most commonly used bandwidth. The 10 and 20 MHz alternatives will provide more capacity, but the occupancies occurring in the desired frequency band set some limits. For example, there may be problems to implement the whole frequency band in several countries. The effective bandwidth for WCDMA is 3.84 MHz, and with guard bands the required bandwidth is 5 MHz. The guard bands are needed to reduce the interference between different 5 MHz WCDMA carriers. Figure 11 shows the WCDMA carrier:
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Fig. 11 A WCDMA Carrier In One Direction
The 3.84 MHz bandwidth in WCDMA is a wider bandwidth available in WCDMA as compared to 1.25 MHz in CDMA and hence the name Wideband CDMA.
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3
Principles of Radio Duplex
3.1
UMTS Frame Structure
The transmission of data in a cell between base stations and mobile stations requires coordination in two aspects. Firstly, during a typical full duplex transmission, the two transmission directions, uplink and downlink, between a mobile station and the base station must be coordinated. Secondly, the transmission between the different mobile stations of a cell and the base station must be coordinated. Two duplex methods, FDD and TDD, are used for coordinating the former aspect. Three multiple access methods FDMA, TDMA, and CDMA are used for coordinating the latter aspect.
3.2
Duplex Transmission: FDD and TDD
In FDD, two separate bands are allocated for transmisssion. One is for uplink transmission from the UE to the BTS, and the second is for downlink transmission from the BTS to the UE.
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Two duplex methods, Frequency Division Duplex (FDD) and Time Division Duplex (TDD), are used for coordinating the Uplink (UL) and Downlink (DL) components of a transmission between a base station and a mobile station. Generally the DL frequency band is positioned at the higher frequency than the UL band.
Principles of UMTS Terrestrial Radio Access (UTRA)
Figure 12 shows each band is specified to be 5 MHz and is separated by 190 MHz:
Fig. 12 Downlink and Uplink Bandwidth in FDD zezenenu.und.lmm/cajaqara.en.slo
In FDD, the users share the same frequency in both transmission directions. The first terminals and networks will support FDD. In TDD, one band is divided into timeslots. The bandwidth is the same at 5 MHz. Instead of separate bands for uplink and downlink, users are allocated to timeslots. Figure 13 describes the Downlink and Uplink Bandwidth in TDD:
Fig. 13 Downlink and Uplink Bandwidth in TDD
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UMTS TDD Mobile Broadband technology designed to work in a single unpaired frequency band. UMTS TDD is based on the international 3GPP Universal Mobile Telecommunication System (UMTS) standard. UMTS is a packet data implementation of this standard and which uses Time-Division-Duplexing (TDD). UMTS TDD does not use FDD (Frequency Division) used by W-CDMA. The biggest advantage provided by TDD is that it supports variable asymmetry, which allows operators to decide the capacity that they want to allot to downlink versus uplink servers. This improves the effectiveness of the available spectrum resources because data traffic patterns tend to heavily favour downlink. Most of the renowned Asian and European mobile operators have spectrum allocated to IMT-2000 TDD technologies.
Another improvement provided by UMTS TDD is its Non Line-Of-Sight characteristic. This allows access from different locations where the tower may not be in the line of sight and its direct view may not be possible. The cell radius supported by UMTS TDD can range from something as small as a microcell to a distance as large as 29km. The UMTS TDD standard provides tower-to-tower handoff and continuous connections for mobile customers even at a speed of 120 km/h and over.
Advantages of UMTS TDD: UMTS TDD Solutions provide enhanced performance by supporting peak downlink sector capacities of up to 12Mbps. Even the average capacities per sector provided by UMTS TDD are thrice as high when compared to other commercial mobile platforms. UMTS TDD solutions are cost effective when compared to other technologies and these costs will reduce further when this globally accepted standard is produced at a higher scale. Even in the current market, operators can profitably offer flat rate broadband services, which provides similar cost and speed when compared to DSL. UMTS TDD improves spectral efficiency with the help of its N=1 frequency reuse standard. This standard allows network operators to deploy a network that uses multiple towers using only one 5 MHz RF channel for a 3.84 Mcps (MegaChip per second) system or one 10 MHz channel for a 7.68 Mcps system.
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In some countries that do not follow the ITU recommendations the UMTS TDD has been rebanded. This provides flexibility for service providers allowing them to operate in other licensed spectrum bands extending up to 3.6GHz.
Principles of UMTS Terrestrial Radio Access (UTRA)
Customers benefit from using UMTS TDD as the installation is extremely easy. If you consider the existing customer base and compare it with a new DSL subscriber, you will find that most of them have performed the provisioning and installation themselves with minimum customer service calls. This itself points to the fact UMTS TDD provides better customer experience. UMTS TDD subscribers also benefit from better connectivity within the network footprint while they are mobile and traveling at a speed more than 120 km/hr. UMTS TDD supports Tower-to-tower handoff as well as network-to-network roaming. The fact that UMTS TDD is already established in the markets, gives it an edge over the other competing technologies, which are still in the development phase.
Standards Compliant: The network operators can use UMTS TDD to provide scalability and support for equipments from multiple vendors. It also provides long-term viability and can use different innovations for products designed by world's leading research teams. There are three standards of UMTS at the air-interface (physical layer), TDD, FDD W-CDMA and TD-SCDMA. All the three standards share higher layer protocol stack and core network architecture. zezenenu.und.lmm/cajaqara.en.slo
TDD is designed especially for high data rate services. The burst structures defined in TDD provide support for advanced signal processing. TDD also allows interoperability among UE and network infrastructure developed by multiple vendors. Over time, this will drive the market to offer more competitive rates and increase innovation, particularly on UE. UMTS TDD solutions can operate in either a single 5MHz channel, or a 10MHz channel. The UMTS TDD standard is inherently designed to support N=1 reuse (a single frequency network) in response to network operators in the IMT 2000 3G band, which are only allocated a single TDD channel. UMTS TDD achieves N=1 by using direct-sequence spread-spectrum, which provides the processing gain required for negative C/I operation.
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4
The Structure of the UMTS Air Interface
The structure of the air interface is quite complex. This chapter starts with an overview of the air interface, the "big picture". It is based on the UMTSFrequency Division Duplex (FDD)implementation. After the overview, we will break up this model and explain the main parts more in detail. The specifications dictate how the information is transferred on the physical interface, including issues like how the data is coded, transmitted, and received on the air interface. These specifications must be supported by the Node B, the Radio Network Controller (RNC), and the User Equipment (UE). The aim is to divide the responsibilities of the RNC and the Node B as much as possible, which may then enable an open Iub interface (Node B-RNC).
4.1
CDMA Sequencing – A Way to Spread Information
CDMA sequencing refers to how the data to be transmitted over the radio path with CDMA technology is spread over the defined frequency band. The following two techniques can be used for CDMA sequencing: 1.
2.
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Frequency Hopping (FH) Sequencing – In this technique the information to be transmitted is located in different parts of the frequency band as a function of time, according to a certain hopping sequence. Direct Sequencing (DS) - In case of DS, the information to be transferred is spread all over the defined frequency band as a function of time, and it appears similar to background noise.
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The terminal is a platform with different applications such as video, voice, and Internet access running on top of it. We can class this as data. The network must also exchange signalling messages with the terminals in order to control the activities of the terminal such as location and connection management.
Principles of UMTS Terrestrial Radio Access (UTRA)
Figure 14 shows the two CDMA sequencing techniques:
Fig. 14 CDMA Sequencing Techniques
The 3G-wideband radio access will use the DS technique. The DS-WCDMA-FDD also requires a certain timing structure, but it is not used as in GSM. The basic DS-WCDMA-FDD frame. Figure 15 describes the DS-WCDMA-FDD Frame: zezenenu.und.lmm/cajaqara.en.slo
Fig. 15 DS-WCDMA-FDD Frame
One basic frame is divided into 15 slots, with each slot measuring 2/3 ms in length. Therefore, the frame length is 10 ms. This timing structure is mainly required for the synchronization signal arrangements and does not impact the channelization. In addition, every WCDMA frame is numbered by the System Frame Number (SFN) according to the 3GPP Specifications. This has been done to ensure the inter-operability between GSM and WCDMA, particularly the inter-system handover.
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4.2
Codes - What and why?
A code is a specific sequence of bits applied to data to scramble it. When the receiving end is monitoring the air interface, it should be possible to retrieve the original data by applying the same code to the coded data. Therefore, the same code must be applied, both, at the transmitting and the receiving end. The WCDMA system uses several codes. In theory, one type of a code should be enough. But, in practice, the radio path physical characteristics require that the WCDMA system should use different codes for different purposes. In WCDMA, two kinds of codes are available, channelisation codes and scrambling codes. Table 2 shows the usage of these codes:
Channelization code
Scrambling code
Uplink: Separation of physical data and control channels from the same terminal Downlink: Separation of downlink dedicated user channels
Uplink: Separation of terminals Downlink: Separation of sectors or cells
Length
Variable depending on the user allocation
Fixed
Number of codes
Depends on the spreading factor (SF)
Usage
Uplink: Several millions Downlink: 512
Table 2
Table 2. Properties of Channelization and Scrambling Codes
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Figure 16 shows the difference between the channelization and scrambling codes:
Fig. 16 Difference between Scrambling and Channelization Codes zezenenu.und.lmm/cajaqara.en.slo
For example, in a radio network each cell is separated by a code. This is roughly comparable to the frequency division method used in GSM. In UMTS, the Primary scrambling code differentiates between different cells. However, as a cell contains physical channels, the channelization code is applied to enable terminals to identify the channel that they are listening to. Several calls can take place at the same time, in the same cell, on the same carrier frequency band. The individual connections are separated at the receiver’s side by the code. A physical channel in the UMTS FDD-mode is uniquely identified by the used frequency band and code.
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Summary of code usage in the uplink and downlink direction : In the downlink direction, you need to differentiate between different cells. The scrambling code is used for this purpose. To differentiate between different users within the cell, the channelization code is used. As a result, only one dedicated physical channel is used in the downlink direction. Both, the signaling information (such as power control commands) and the application data must be mapped onto this physical channel. In the uplink direction, you do not need to differentiate between cells. Therefore, the scrambling code can be used for differentiating between users.As a result, the channelisation code can be used to differentiate between different channels.
4.2.1
Chip and Symbol – Two Kinds of Bits
A symbol is a data unit transmitted over the Air Interface. In the downlink transmission, each symbol represents two bits can be represented as a tuple (x1, y2). In the tuple, x1 and y2 each represent one bit. Every subsequent symbol can be represented as a tuple and delivers two new bit values. For example, the next symbol can be represented as (x2, y2) and delivers two new bit values. Uplink transmission also uses symbols and represents them as tuples. However, unlike in case of downlink transmission, in the case of uplink transmission the symbol at the first position can have a different data rate as compared to the symbol at the second position. For example, the first symbol can be (x1,y) and the second symbol can be (x2,y). The symbol rate indicates the number of symbols transferred over the radio path. It is expressed as kilo symbols per second (ks/s). downlink, if the symbol rate is 480 kilo symbol per second, the bit rate is 960 kilo bit per second. uplink, if the symbol rate is 480 kilo symbol per second, the bit rate is 480 kilo bit per second (first position in the tuple) plus 15 kilo bit per second (second position in the tuple, which has a fixed data rate). A chip is a bit of the code signal used for signal multiplication. The code signal bit rate, which is hereafter referred to as the chip rate, is fixed in WCDMA at 3.84 million chips per second (Mcps/s). With this chip rate the size of one chip in time is 1 / 3 840 000 seconds. One way to better understand the meaning of the terms symbol and chip is to study the simplified example.
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Two important concepts of WCDMA are chip and symbol that help you to understand the structure of the air interface. The basic idea behind WCDMA is that the signal to be transferred over the radio path is formed by multiplying the original, baseband digital signal with another signal, which has much greater bit rate. Both the signals consist of data units, chip and symbol, and you must clearly distinguish between the data units of the two signals.
Principles of UMTS Terrestrial Radio Access (UTRA)
Figure 17 illustrates Chip and Symbol in Binary Phase Shift Keying:
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Fig. 17 Chip and Symbol in Binary Phase Shift Keying
4.3
Rate Matching
After the error protection, the baseband data rate is matched to the bearer bit rates used in the UMTS Air Interface. The data rates are given with the available channelization codes with their respective spreading factors. Figure 18 describes the different bit rates between 15 and 960 Kbps that may be applied for user data:
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Fig. 18 Adaptation of the Bit Rate for the UMTS Air Interface
In cases where the bit rate is higher than a certain allowed bit rate, puncturing can be performeed. Puncturing means the removal of some of the redundant bits from the channel coding, thereby reducing the bit rate to the desired level. Assume that you want to send some baseband data from a Node B to a user. This data has already been subject to channel coding and rate matching. The rate matched baseband data or symbols in have the values -1 or 1. The –1 is actually a zero (0) bit symbol. This conversion has to be made, since we will multiply the symbol with the code chips and multiplying with (0) zero would be useless. One baseband bit, which is the symbol, will be multiplied with eight code chips. The code has a chip rate of 3.84 Mega chips per second. This is referred to as spreading, and the spreading factor (SF) in this example is thus 8. By knowing these values, you can calculate the symbol rate as 3.84 Mcps / 8 = 480 Kilo symbols per second. Downlink, QPSK is applied and the symbol rate is 480 ks/s and consequently the bit rate is 980 kilo bit per second. When the data is spread, at the same time it is combined with a channelization code. The baseband data is spread by 'chipping' the data. For example, if we use a factor of 8 to spread 010, the result would be 000000001111111100000000, without combining with the channelization code. The collection of these chips (etc. 11111111) is therefore the same as the symbol. This is a signal processing function.
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The bit rates are not the same as the application or user data rates. To exemplify this, imagine a speech call at 12.2 kilo bits per second. These bits must undergo channel coding in order to enable error correction. After the convolutional channel coding, the bit rate is approximately 24 kbit/s. Now, you need to rate match this data to the closest allowed bit rate in UMTS, which in this case is 30 kbit/s, as shown in Figure 17. Some of the encoded data bits are repeated according to a certain pattern in order to increase the bit rate to the desired level.
Principles of UMTS Terrestrial Radio Access (UTRA)
Figure 19 shows how data is spread and combined with channelization code:
Fig. 19 Spreading Data and Combining it with Channelization Code zezenenu.und.lmm/cajaqara.en.slo
The scrambling code is applied to the data after the channelization code, and it does not change the actual chip rate, which remains 3.84 Mcps/s. As mentioned earlier, the role of the scrambling code is to separate users in the uplink. In the downlink direction, it is used to separate the different cells.
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Figure 20 shows the consecutive process of applying the channelization code and scrambling codes to the data:
Fig. 20 Applying Channelization Code and Scrambling code to the Data
You will next learn more about spreading factor, channelization codes, and scrambling codes.
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Once the signal arrives in the User Equipment (UE), we can spread it by applying the same scrambling and channelization codes as when the spreading took place.
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4.4
Spreading Factor
Spreading factor is a multiplier describing the number of chips used in the WCDMA radio path per one symbol. Spreading factor K can be expressed mathematically as follows: k
K = 2 , where k = 0, 1, 2 … 8 For instance, if k = 6, the spreading factor K is 64, indicating that one symbol uses 64 chips in the WCDMA radio path. Another name for spreading factor is processing gain (G p ), and it can be expressed as a function of used bandwidths. B U U G p = ---------------------- B Bearer System Chip Rate ------------------------------- = Spreading Factor Bearer Symbols Rate zezenenu.und.lmm/cajaqara.en.slo
In the formula, B Uu is the System Chip Rate and B Bearer is the bandwidth of the rate matched baseband data. The B Bearer contains already excessive information, such as channel coding.
4.4.1
Further Examination of Scrambling and Channelization Codes
Channelisation and scrambling codes are also known as gold codes. In WCDMA, there are 512 primary codes as limited by the specification body to reduce the amount of scanning. The scrambling codes are divided into 512 code sets, each of them containing a primary scrambling code and 15 secondary scrambling codes.
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Figure 21 illustrates Scrambling Code Arrangement:
Based on the code selection method, there are altogether 8192 scrambling codes available in downlink direction and millions in the uplink direction. Each primary/secondary code has associated with itself a set of channelization codes. While using the highest spreading factor, it can support 256 channels.
4.5
Scrambling Code
Only one primary scrambling code is allocated for a cell. The Primary CCPCH, which carries the cell information on the logical BCCH channel, is transmitted by using the scrambling code. The other downlink physical channels may use either the primary scrambling code or a secondary scrambling code from the set associated with the primary scrambling code of the cell. In the uplink direction, there are millions of scrambling codes available. All uplink channels may use either short or long scrambling codes. Long codes are used if the base station uses the RAKE receiver. In the downlink direction, always long scrambling codes are used.
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Fig. 21 Scrambling Code Arrangement
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4.6
Channelization Code
Channelization codes are used for channel separation both in uplink and downlink direction. In the downlink direction, only one dedicated physical channel is shared by the signaling and the application data. As a result, channel separation is the same as the user separation. Channelization codes have different spreading factor values and therefore different symbol rates. There are a total of 256 short codes available under certain conditions. The channelization code length is one symbol. For example, if the spreading factor is 4, then the channelization code contains 4 chips. One baseband bit of data in the air interface is therefore described with a 4-chip code. The channelization codes have orthogonal properties. Orthogonal means that the channelization codes in the 256-member code list are selected so that their interfere with each other is minimal. This is necessary in order to have a good channel separation. Unlike channelization code, the scrambling code used for user and cell separation have good correlation properties. The scrambling codes do have these characteristics, and this is the basic reason why both scrambling and channelisation codes are used. zezenenu.und.lmm/cajaqara.en.slo
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Figure 22 shows the WCDMA Code Tree:
Every WCDMA cell uses one downlink scrambling code, which is locally unique and acts like a cell ID. The characteristic of this scrambling code is pseudo-random; it is not always orthogonal. Under this scrambling code the cell has a set of channelization codes, which are orthogonal in nature and used for channel separation purposes.
4.7
Receiving Signals at the Terminal
The environment consists of various obstructions for the mobile communication, such as buildings, trees, hills, and water. This presents a problem of multipath signals. A signal from a Node B to a mobile is often not direct, as there are objects standing in the way. When a signal is reflected by these objects, it will arrive at its destination later than the other signals.
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Fig. 22 WCDMA Code Tree
Principles of UMTS Terrestrial Radio Access (UTRA)
Figure 23 describes Multipath Signal Problem:
Fig. 23 Multipath Signal Problem
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In WCDMA, the terminal employs a RAKE receiver to handle multipath propagation. The RAKE consists of receiver(s), adjustable-by-system delay functionality, code generator, and gain and phase tuning equipment. One multipath component that the RAKE recognizes is called a finger. Typically, RAKE is able to handle several fingers. One of these fingers receives the signal from the Uu interface and tries to open it with the code used for the connection. The second finger receives the same signal from the Uu interface, and the code used for this connection is inserted to the receiver after a short, adjustable delay. When the signal is demodulated and regenerated, the outcomes of the fingers can be summed together. Why is the RAKE receiver capable of detecting several multipath and reading the user data on individual multipaths? The scrambling code is a pseudo-noise sequence and has no repeating pattern. Because of this, the RAKE receiver not only determines the multipaths but also their run-time difference. Each RAKE finger holds a code generator, which can be synchronized to one incoming multipath. The data carried on the multipath can be retrieved. This process is repeated on every RAKE finger. The individual multipaths may have a very low receive level and the data, which is still in form of samples of the electro-magnetical wave is inaccurate. After adjusting the run-time difference of the multipaths in each RAKE finger, the individually weak multipath results are combined, resulting in a comparatively strong result.
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There are two benefits: First of all, the transmission output power can be low in comparison to GSM, because the receiver can retrieve the user data by combining the information carried on several multipaths. This has a direct impact on the radio interface capacity, where the transmission of all active users takes place at the same time. Secondly, and only in the FDD-mode, a UE can be connected to several cells or Node B simultaneously. Each cell or Node B is hereby sending the same data downlink to the UE. In other words, several cells are used to create a multipath propagation situation. The RAKE receiver in the UE can generate the different codes, used by different cells on the individual RAKE fingers.
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Figure 24 shows the composition of the RAKE receiver:
Fig. 24 Simplified Block Diagram of the RAKE Receiver
The RAKE receiver located in the UE, uses three fingers for multipath reception. The fourth finger is reserved for environment observation. The reason for this behavior is that in WCDMA, the UE may have active radio connections simultaneously through three cells. The RAKE fingers are responsible for the de-spreading of the user signals received by multipath propagation. The fingers also correct the information with regard to phase and adapt the timing of the information. Depending on the signal strength, the information components are summed (Maximum Ratio Combining). A strong signal consisting of multipath components is therefore obtained in this way with a RAKE receiver.
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Applications produce a stream of bits, which is the data, to be transmitted. The resource requirements mainly depend on the type of the application. One of the main benefits with the UMTS Air Interface is the possibility to allocate resources according to the need of the application. However, before the application data or signaling is transmitted, the data needs to be prepared for transmission. The first step in this process is to map the data to the correct logical channel, map the data to the correct transport channel, apply the channel coding to the data, match the bit rate, and finally map the data to the correct physical channel.
4.8
Channel Coding
Figure 25 shows channel coding step in the process of preparing data for transmission over the UMTS Air Interface.
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Fig. 25 Channel Coding
Channel coding is done in order to improve transmission quality in the air interface in case of problems, such as interference and low reception levels. This is possible by adding redundant bits to the signal to increase the bit rate.
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In UMTS, both 1/2 and 1/3 rate convolutional coding, as well as so-called turbo coding, will be implemented.
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1/2 rate coding means that there is roughly one redundant bit for every real bit. Similarly, the 1/3 rate channel coding leads to a three-fold bit rate. Turbo coding is a new channel coding method that is used mainly for applications that require high bit rates. Turbo coding is a fast convolutional coding method with a coding rate of 1/3.
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5
UMTS Channel Structure
5.1
Logical Channels
UMTS uses a three-layer concept for channel organization, consisting of the Logical Channels, Transport Channels, and Physical Channels. A set of logical channels is defined in UMTS for different types of data transfer services. Each logical channel is defined by the type of data that has to be transmitted. The application and signaling procedures use logical channels to communicate with the mobile network. Different logical channels are used for different purposes. For example, there are channels for carrying paging information for all idle UEs in the cell, channels dedicated to UEs for signaling, and channels dedicated to individual UEs for user data transfer. Logical channel are specified for uplink and downlink transmission. Each logical channel transmits a specified content or it is used for a well defined task.
5.2
Transport Channels
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Transport Channels are a new concept in UMTS. They are channels in between the logical channels and the physical channels. These transport channels are needed to describe how logical channel data is organized for transport. Transport Channels are defined by how and with what characteristics data is tranmitted over the network. Different Logical Channels can be mapped together onto one Transport Channel. The Transport Channels are interface between MAC and Layer 1, while Logical Channels are interface between MAC and RLC. The logical and transport channels define WHAT data are transported, while the physical channels define HOW and with what physical characteristic the data are transport.
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The Transport Channels can be sub-divided into the following two general classes: 1. 2.
Common Transport Channels: In this case when there is a need for in-band identification of the UEs when particular UEs are addressed. Dedicated Transport Channels: In this class of Transport Channels the UEs are identified by the physical channel. The physical channels are characterized by the code and frequency of the FDD mode, and code, time slot, and frequency for the TDD mode.
5.3
Physical Channel
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Physical Channel define the physical transmission of the information over the Air Interface. In UMTS physical channels of the UTRA FDD mode are characterized by the code and UL and DL frequency. The physical channels of the TDD mode are characterized by code, frequency, and time slot.
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Figure 26 shows the three channels of the UMTS Air Interface:
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Fig. 26 Physical, Transport and Logical Channels in the UMTS Air Interface
The physical channels are present in the air interface, while the transport channels and the logical channel structure are valid in all the interfaces between the User Equipment (UE) and the Radio Network Controller (RNC), as illustrated in figure 24. Each physical channel is identified in the FDD mode by the frequency band used for the transmission and by a spreading code.
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Figure 27 gives a few examples of the path of data and signaling through the channels:
5.4
Description of the UMTS-FDD Logical and Transport Channels
In case of Logical Channels, the UE and the network have different tasks. Therefore, the logical channel structure is different in the downlink and uplink direction. The network has the following tasks to perform: 1.
2.
3.
4.
5.
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Broadcast Control Channel BCCH general network information delivery: DL The network must inform the UE about the radio environment. The network provides information, such as the code value(s) used in the cell and in the neighbouring cells and the allowed power levels, for the UE through the Logical Channel, BCCH. Paging Control Channel (PCCH) paging purposes: DL When there is a need to reach a UE for communication, such as when a mobile call is terminated, the UE must be paged in order to find out its exact location. This network request is delivered on the Logical Channel, PCCH. Common Control Channel (CCCH) control purposes The network may have certain tasks that may be common for all the UEs residing in the cell. For this purpose the network uses the Logical Channel, CCCH. Dedicated Control Channel (DCCH) control purposes When there is a dedicated, active connection, the network sends control information through the Logical Channel DCCH. Dedicated Traffic Channel (DTCH) dedicated traffic purposes The dedicated user traffic for one user service in the downlink direction is sent through the Logical Channel, DTCH,.
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Fig. 27 Mapping of User Data and Signaling from the Node B Point of View
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6.
Common Traffic Channel (CTCH) common traffic purposes When there is a need to transmit information either to all UEs or to specific group of UEs, then a downlink-only Logical Channel CTCH can be used.
The logical channels must be mapped into the transport channel structure. Following Transport Channels are carrying the ready-made information flows in the downlink direction: 1. 2. 3.
4.
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5.
Broadcast Channel (BCH) - This Transport Channel carries the Logical Channel BCCH. Paging Channel (PCH) - This Transport Channel carries the Logical Channel PCCH. Forward Access Channel (FACH) – This Transport Channel carries information coming from the common and dedicated control Logical Channels, CCCH, CTCH, and DCCH. Dedicated Channel (DCH) – This is the only dedicated Transport Channel; all other channels are common Transport Channels. The DCH carries information coming from the Logical Channels DTCHs and DCCH. In some case, one DCH may carry several DTCHs, depending. For example, a user may have a simultaneous voice call and video call active. The voice call uses one DTCH and the video call requires another DTCH. Both of these, however, use the same DCH. Downlink Shared Channel (DSCH) - This Transport Channel carries dedicated information from the Logical Channels DTCH and DCCH. This channel is shared by several users.
In the uplink direction the number of logical channels required is less as compared to downlink direction. There are only three logical channels, CCCH, DTCH and DCCH, as shown in Figure 3-27. These abbreviations have the same meaning as in the downlink direction. The following are the transport channels in the uplink direction: 1. 2. 3.
Random Access Channel (RACH) - This Transport Channel carries initial access information when required. Dedicated Channel (DCH). This Transport Channel carries the combination of the user traffic(s) and control information. Common Packet Channel (CPCH). This Transport Channel carries user packet(s) if the common resources of the system are used for this purpose.
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5.5
UMTS-FDD Transport to Physical Channels
When the information is collected from the logical channels and organized to the transport channels, it is in ready-to-transmit format. Before transmitting, the transport channels are arranged to the physical channels. A physical channel is defined by the used frequency band and the used CDMA code. There are some physical channels that have no logical and transport channels. Therefore, in the downlink direction, they are directly generated in the Node B.
With the help of the Primary and Secondary Synchronization Channels, the UE can perform chip, timeslot, frame, and scrambling group synchronization. There are 512 primary scrambling codes used in the downlink direction. They are organized in 64 scrambling code groups, where each group is holds eight primary scrambling codes. Therefore, the UE only knows the scrambling code group, but not the scrambling code of the cell. Eight potential primary scrambling codes may be in use in a cell. To identify the correct scrambling code, the UE uses the Common Pilot Channel (CPICH). The CPICH always uses the same channelization code (CCH,256,0), so that the UE can determine the cell’s scrambling code by trial and error. The following are two Common Control Physical Channels: 1.
2.
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Primary channel (CCPCH-1) – This Physical Channel carries broadcast control information. This is the same type of information that the GSM BCCH carries. The UE knows the scrambling code of the cell. The channelization code for the CCPCH-1 is always CCH,256,1. Every other physical channel, both uplink and downlink requires a CDMA code, which is the product of spreading code and channelization code. The UE uses the broadcast information to identify the codes that are used in downlink direction, for the random access, and the common control channels. Secondary channel (CCPCH-2) - This Physical Channel carries it carries paging related information and the information currently included in the FACH. Therefore, it acts as a combination of two transport channels. The two dedicated physical channels are Dedicated Physical Data Channel (DPDCH) carrying user traffic, and Dedicated Physical Control Channel (DPCCH) carrying related control information. When these are timely multiplexed together, the combination is called Dedicated Physical Channel (DPCH).
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An example of such physical channels is the Primary and Secondary Synchronization Channels (SCH-1 and SCH-2) that help the mobile phone to synchronize the Node B. Both physical channels are identified by well known scrambling codes.
Principles of UMTS Terrestrial Radio Access (UTRA)
The transport channel RACH carries the initial access information when the UE accesses the network. This information is transferred to the network through the Physical Random Access Channel (PRACH). The random access is decomposed into two components. The first part of the random access begins when the UE sends a set of preambles, each with a higher output power then the preceding one. This is done to avoid interference of the transmission of all UE in the cell and in the neighboring cells. In WCDMA all UE use the same frequency band at the same time. If a UE is making the random access with a too high output power level, the transmission of all UE in the cell and in the neighboring cells can interfere with each other. If the Node B as filtered out the preamble, it returns a short notice to the UE with the Acquisition Indication Channel (AICH; downlink only). After this the second part of the random access begins, where the UE sends more information to UTRAN. The user traffic and control information share a transport channel DCH. The information the DCH carries is divided into two physical channels, DPDCH and DPCCH, with the modulation method used. When there is a need to send a short packet and dedicated resources are not necessary, the information to be sent is carried by the transport channel CPCH. This information is sent through the Physical Common Packet Channel (PCPCH). zezenenu.und.lmm/cajaqara.en.slo
In the uplink direction, the physical channel is not time multiplexed since in combination with Discontinuous Transmission (DTX), it would cause audible interference to non mobile network equipment. The DPCCH is never turned of. As a result, no transmission pulse causes additional interference. The DPDCH uses the DTX periods to save battery and add efficiency to transmissions.
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6
The Key Functions and tasks in Radio Resource Management
6.1
Overview of Radio Resource Management Functions
The Radio Network Controller (RNC) has similar functionality as the BSC in the GSM BSS but there are also a few differences. Unlike the GSM systems, the Radio Access Network (RAN) has RNC-RNC interface (Iur), which enables the RNC to maintain Radio Resource Management (RRM) independently. The wideband switching in the RNC makes the element structure of RNC remarkably different to element structure of BSC in GSM BSS during implementation.
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Figure 28 illustrates the parts of RNC:
Fig. 28 General Diagram of the RNC
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The RNC has different functions to control the radio resource connection. The functions are divided into network and connection based functions. The connection based functions are related to task that RRM performs on an active bearer connection, whereas then network based functions are used continuous in a cell for all allocations. The examples of network based functions are Admission Control (AC), Load Control (LC), Resource Manager (RM), and Packet Scheduler (PS). AC and LC are used to manage the amount of power being transmitted and the number of subscribers in a cell. This control is important when introducing new bearer allocations into the network. The RM is responsible for the allocation of the bearer. Figure 29 explain Radio Resource Management Functions:
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Fig. 29 Summary of Radio Resource Management Functions
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Unlike in GSM, the UMTS network uses packet data inherently, which means that is the packet data is built into the system, rather than being added , Therefore, the PS transmits the data in a cell at the optimal time. The connection based power control (PC) is critical for managing air interface bearers, as more interference in a cell caused in the uplink from mobile to the network, the less overall capacity there is. Therefore, the network is constantly (~1500 per second) informing the mobile station what power level it should use. Handovers are used to manage the reallocation of the bearer as the subscriber moves. Therefore, the entities in the 3G RAN RRM are:
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Radio Resource Control (RRC) Admission Control (AC) Code Allocation Power Control (PC) Packet Scheduler (PS) Handover Control (HC) Macro Diversity
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6.2
Radio Resource Control States
The RRC has two main states, idle and connected. From the UE to network connection point of view, the RRC changes its state from idle to connect. For any activity between the UE and the network, the RRC-connected state can be considered as a prerequisite. When there is no RRC connection between the mobile and the network, but the mobile is switched on, the mobile is considered to be in an idle mode. It means that the mobile is listening to one base station and is in readiness to start a connection, or is waiting to be paged. Figure 30 shows the possible state changes of the RRC protocol:
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Fig. 30 The possible state changes of the RRC protocol
When a dedicated channel is provided to the subscriber, for example, for video, the subscriber is considered to be in the Cell_DCH state. (The DCH is derived from the name of the channel in the air interface). In this state the UE is sending measurement reports to the network, which enables the system to control the dedicated bearer and perform handovers. If the mobile is only sending small pieces of information to the network, for example irregular Internet based traffic or for signalling, then the RRC can be in a mode known as Cell_FACH (the FACH stands for Forward Access Channel) and is different from the previous state as UE is not using dedicated channel. The
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network does not perform handovers as the mobile moves from one cell to another. The UE just informs the network about its current location. Depending on the bearer we have and how it is being used, the RNC will move the RRC between the different states. In addition to the Cell_FACH, if the network finds that the bearer is not being used for a long time, it can move the connection to a Cell_PCH mode (Paging Channel), where the mobile is still know to a cell level but can only be reached via the PCH. In this state the UE is using a Discontinuous Repetition Function, DRX to save battery. Again, unlike in the Cell_DCH, as the subscriber moves, the mobile informs the RNC which cell it has moved to. The final state is the URA_PCH. This state is similar to the Cell_PCH. But, instead of monitoring the connection on a cell level, it is now on a RNC level. URA stands for UTRA Registration Area and the UE monitors the broadcast channel for URA identities.
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The RRC as an entity consists of two items, Medium Access Control (MAC) and Radio Link Control (RLC). Together these two are also called as Layer 2 processing.
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Figure 31 shows the Layer 2 Processing:
Fig. 31 Layer 2 Processing zezenenu.und.lmm/cajaqara.en.slo
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The Physical Layer, in the layer 1 offers Transport Channels to the MAC layer. There are different types of transport channels with different characteristics depending on the transmission. Common transport channels can be shared by multiple handsets (for example, FACH, RACH, DSCH, BCH, and PCH). Dedicated transport channels (DCH) are assigned to only one handset at a time. The transmission functions of the physical layer include channel coding and interleaving, multiplexing of transport channels, mapping to physical channels, spreading, modulation and power amplification, with corresponding functions for reception. A frequency and a code characterize a physical channel.
For common transport channels, the MAC layer adds addressing information to distinguish data flows intended for different handsets. One major difference to GSM is the possibility to dynamically switch one logical channel (data flow) onto different transport channel types, based on the activity of the subscriber. The Radio Link Control (RLC) protocol, a layer 2 protocol, operates in one of three modes: transparent, unacknowledged, or acknowledged mode. It performs segmentation/re-assembly functions and, in acknowledged mode, provides an assured mode delivery service by use of retransmission. RLC provides a service for the RRC signalling to both, the Signalling Radio Bearer and for the user data transfer, the Radio Access Bearer. Above these layers the Radio Resource Control (RRC) protocol, in the layer 3 provides control of the handset from the RNC. It includes functions to control radio bearers, physical channels, mapping of the different channel types, handover, measurement and other mobility procedures.
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The MAC protocol, in the layer 1 offers logical channels to the layers above. The logical channels carry different types of information, which include Dedicated Control Channel (DCCH), Common Control Channel (CCCH), Dedicated Traffic Channel (DTCH), Common Traffic Channel (CTCH), Broadcast Control Channel (BCCH) and the Paging Control Channel (PCCH). The MAC layer performs scheduling and mapping of logical channel data onto the transport channels provided by the physical layer.
Principles of UMTS Terrestrial Radio Access (UTRA)
7
List the Roles of Radio Resource Management on Network
7.1
Admission Control
WCDMA radio access has several limiting factors, some of them being absolute and others environment-dependent. The most important and the most difficult is to control is the interference occurring in the radio path. Due to the nature and basic characteristics of WCDMA, every UE accessing the network generates a signal. Simultaneously, the signals generated by UE can be interpreted to be interference from the other UEs point of view. When the WCDMA network is planned, one of the basic criteria for planning is to define the acceptable interference level, with which the network is expected to function correctly. This planning based value and the actual signals the UE transmit set practical limits for the Uu interface capacity. zezenenu.und.lmm/cajaqara.en.slo
To be more specific, a value called Signal-to-Interference Ratio (SIR) is used in this context. Based on radio network planning, the network is, in theory, able to stand as maximum one SIR of certain size within one cell. That is, in the BTS receiver, the interference and the signal must have a certain level of power difference in order to extract one signal out from the other signals using the same carrier. If the power distance between interfering components and the signal is too small, the BTS is not able to extract an individual signal out from the carrier any more. Every UE having a bearer active through this cell “consumes” a part of the SIR. The cell is used up to its maximum level when the BTS receiver is not able to extract the signal(s) from the carrier.
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Figure 32 shows the Admission Control (AC):
The main task of admission control is to estimate whether a new call can have access to the system without sacrificing the bearer requirements of existing calls. Thus the AC algorithm should predict the load of the cell if the new call is admitted. It should be noted that the availability of the terrestrial transmission resources is verified, too, meaning that there is no limiting factor in the rest of the UTRAN either. Based on the admission control, the RNC either grants or rejects the access. The SIR or Interference Margin has direct relationship with the cell load. If we express the cell load with a Load_Factor (from 0 to 1, equals cell percentage load, that is, 10 % load gives value 0.1) and mark the Interference Margin with I, it leads to the following equation:
Fig. 33
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Fig. 32 Admission Control (AC)
Principles of UMTS Terrestrial Radio Access (UTRA)
Figure 33 shows the placing of Interference Margins calculated with different Load Factor values together:
Fig. 34 Interference Margin as a Function of a Cell Load
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Based on the above graph, it is fairly easy to indicate that when the cell load exceeds 70 %, the interference in that cell will be very difficult to control. This is why the WCDMA radio network is normally dimensioned with expected capacity equivalent to Load Factor value 0.5 (50 %). This value has a safety margin in it and the network will behave as expected.
7.2
Planning Uplink Admission Control
The RNC controls the interference on the uplink, and the parameters are used to act as boundaries. The UL interference power, which determines the maximum limit where the cell is considered to be at maximum load. From the graph depicting, interference margin as a function of a cell load, a realistic value to represent a sensible load can be arrived at The value is known as the PRX_Target (PRX stands for Receive Power level.) value. The area from 0 to this value is known as the planned load. Once the load is approaches this value, the Traffic Reason Handovers (TRHO) are performed.
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Figure 34 shows the Admission Control on the Uplink:
Fig. 35 Admission Control on the Uplink
7.3
Code Allocation
This section aims to further specify the properties and usage of the scrambling and channelisation codes in Radio Resource Management (RRM). The different codes used in WCDMA were briefly explained in the chapter earlier This section aims to further specify the properties and usage of the scrambling and channelisation codes in RRM. Both scrambling and channelisation codes used in the Uu interface connections are maintained by the RNC. In principle, the codes could be maintained by the BTS, but then the system would experience lack of radio resource control such as soft handovers. When the codes are maintained by the RNC, it is easier to allocate Iub data ports for multi path connections. The Uu interface requires two kinds of codes for proper functionality. A part of the codes used must correlate with each other to a certain extent, and the others must be orthogonal. Every cell uses one scrambling code. As you already know, this code acts like a cell ID. Under every scrambling code the RNC has a set of channelisation codes. This set is the same under every scrambling code. The BCH information is coded with a scrambling code value, and thus the UE must first find the correct scrambling code value first in order to access the cell. When a connection between the UE and the network is established, the channels used must be separated. The channelisation codes are used for this purpose. The information sent over the Uu interface is spread with a spreading code per channel. Spreading code by definition is the same as scrambling code x
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As UMTS traffic is variable and constantly changing, it is possible that the traffic admission may exceed the PRX_Target. To handle this situation, a second level of value known as the PRX_TARGET_BS is used by the BTS to stop situations of congestion. Once this value is reached, the BTS takes actions to reduce the load in the cell.
Principles of UMTS Terrestrial Radio Access (UTRA)
channelisation code.
7.4
Channelisation Code Allocation, and Handovers
The codes used in Uu interface can be handled in a code tree, where branches are consequently blocked when a certain code on a certain spreading factor level is taken into use. When having plenty of simultaneous connections, with multiple radio links, multiple channels, and multiple codes, the code tree may easily become fragmented. Fragmentation means the phenomenon where the probability of the blocked branch of the code tree increases too much and thus it starts to prevent new accesses to the system. For example, if an active call uses high bit rate over the Uu interface, the spreading factor value in use is small. It furthermore means that a very high-level branch of the code tree is blocked. When this call is finished and simultaneously new calls access the system, the blocked code tree branch is not “released” before the new accesses. In this situation the system wastes capacity because the code channels allocated for new calls are not necessarily allocated in the best possible way. zezenenu.und.lmm/cajaqara.en.slo
The channelisation code used has the same length as the base band data. As a part of the spreading operation, the base band data and the code are combined and spread. The result is a fixed length code that is then scrambled. A low data rate communication can be spread much more over the bandwidth, which also means that a high spreading factor is used.
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Figure 35 explains the Channelisation Codes:
As codes are released in different branches, the tree can become fragmented and the RNC should always try to reorganize the tree to make the best use of the resources. Therefore, in UMTS networks, it is possible that the channelisation codes could change during a connection. Also, if the scrambling code in the uplink is being used by another person in another RNC as the subscriber performs a soft handover, the handover is refused and the serving RNC must allocate a new scrambling code to the subscriber.
7.5
Scrambling Code Planning
There are totally 512 downlink scrambling codes used, eight in each of the 64 code groups. All the cells that the UE is able to measure in one location should have different scrambling codes. To ensure this, different scrambling code groups in the neighboring base stations should be used. The code group allocation is performed during the network planning. The corresponding functionality should be present in the network planning tool. The number of re-uses could be 64, as there are 64 code groups. The scrambling code group planning for different frequency carriers can be done independently.
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Fig. 36 Channelisation Codes
Principles of UMTS Terrestrial Radio Access (UTRA)
7.6
Power Control
In the UTRAN, the power control and accuracy is extremely essential (unlike in GSM networks). The reasons can be as follows: The mobiles transmit simultaneously in time (not in different timeslots like in GSM). The UTRAN uses often only one frequency, which means that the. The frequency re-use factor will be 1. Any inaccuracy in power control immediately increases interference, which then decreases the capacity of the network. Figure 36 shows the Power and Distance:
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Fig. 37 Power and Distance
The physical facts in the UTRAN with regard to the radio path and the distance are similar to the GSM, but because of the three reasons stated above, the power control mechanism must be accurate and fast. As a result, the WCDMA power control mechanism differs from the GSM mechanism. It is relatively easy to determine that the optimal situation from the Node B receiver because the power representing one UE’s signal is always equal when compared to the other User Equipments' s signals, despite the distance between the UE and the Node B. As a result, the SIR will be optimal and the Node B receiver is able to decode the maximal number of transmissions. The power control mechanisms used in the GSM are inadequate to guarantee this situation in WCDMA. Therefore, the WCDMA has a different approach to the power control.
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Figure 37 shows the different WCDMA Power Control mechanisms :
7.6.1
Open Loop Power Control
When the UE accesses to the network, the initial level for accessing is based on an estimate. This estimate in turn is based on the signal level received from the Node B when the UE is in the idle mode and the downlink power level that the UE detects from the physical channel PICH. In other words, when in an idle mode, the UE receives information about the used and allowed power levels from the Pilot Channel of the cell. In addition, the UE evaluates the path loss occurring compared to the figures received from the CCH-1. Based on this difference, the UE is able estimate the correct-enough power level to initialize the connection.
7.6.2
Closed Loop Power Control
When the radio connection is established, the power control method is changed. During the connection, the method used is called the closed loop power control. Within this method, the Node commands the UE either to increase or to decrease its transmission power with the pace of 1.5 kHz (1500 times per second) in the FDD mode. The decision whether to increase or decrease the power is based on the received SIR estimated by the Node B.
7.6.3
Outer Loop Power Control
Due to the macro diversity, the UE is simultaneously attached to the network through more than one cell. The RNC must be aware of the current radio link conditions and quality. The RNC knows the allowed power levels of the cell and target SIR.
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Fig. 38 WCDMA Power Control Mechanisms
Principles of UMTS Terrestrial Radio Access (UTRA)
In order to maintain the quality of the radio link, the RNC uses this power control method to adjust the SIR of the connection. By doing this, the network is able to compensate changes in the air interface propagation conditions and to achieve the target quality for the connection. The target quality can be measured with the help of Bit Error Ratio (BER) and Frame Error Ratio (FER) observations.
7.7
Packet Scheduler
Packet scheduler is a general feature, which handles scheduling radio resources for Non-Real-Time (NRT) radio access bearers for both uplink and downlink directions. Packet access is implemented for both dedicated (DCH) and common control transport channels Random Access and Forward Access Channels (RACH/FACH). Packet scheduler makes the decision of the used channel type for the downlink direction. For uplink direction the decision of the used channel type is made by the UE. Figure 38 illustrates function of the packet scheduler:
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Fig. 39 Function of the packet scheduler
In Release 3, the actions of the packet scheduler are driven by the load control function. The gap between Real-Time (RT) traffic and the load target of the cell can be filled by the packet scheduler. As IPv6 is implemented, and Quality of Service (QoS) becomes a key part of the interface, the scheduler no longer sees the traffic as real-time and non-real-time, but instead uses a priority system on the packets being transmitted.
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7.8
Handover Control and Macro Diversity
UMTS handovers can be intra-system, (inside the WCDMA radio network) or inter-system (from WCDMA to GSM 900/1800). The Inter-System Handovers (ISHO) are of the traditional type, which are also used in GSM. The ISHO are also known as a hard handover, because the UE does not maintain simultaneous connections, in practice it breaks the old connection and then establishes a new connection.
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Figure 39 illustrates The Intra-System and Inter-System Handovers:
Fig. 40 The Intra-System and Inter-System Handovers
The intra-system handovers of UMTS are classified as being inside the same WCDMA band (intra-frequency) or being from one frequency band to another. The inter-frequency handover could be a handover from one cell layer to another. The inter-frequency handovers are hard handovers and are similar to the inter-system handovers. The intra-frequency handovers, on the other hand, could be so-called soft handovers. In a soft handover, the signal is received in both the new and the old channel for a period of time. One characteristic of a UMTS network is that the network will communicate with the UE through different base stations (Node Bs). An active set is a list of cells, through which the UE has a connection to the network, that is, through which the radio link set-up has been made.
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This is, the UE may have active radio connection between itself and the network through three cells simultaneously. In soft handover, the UE is connected to the at least two Node Bs at the same time. In the uplink direction, the two signals come via the base stations to the RNC. In the RNC the signal to be transported forward to the core network is selected. The selection is done frame by frame for the speech, and in smaller blocks for data. In the downlink direction, the UE uses the RAKE receiver to combine signals from two different base stations. Figure 40 illustrates the Soft Handover and Active Node B Set:
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Fig. 41 Soft Handover and Active Node B Set
If the subscriber moves from cell site 1, Node B1 to cell site 2, Node B2, first the UE has a connection through Node B1. The power level and Signal to Interference Ratio decreases as the UE moves towards Node B2. At some point the Node B2 signal is high enough and the UE starts to talk via both Node B1 and Node B2. The signal via Node B2 gets clearer and the signal via Node B1 gets worse. Therefore, when the UE talks through two Node Bs, we have macro diversity.
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Figure 41 illustrates the soft handover:
In the next few sections, a clearer subdivision of the different types of handovers is presented. After that, the terms micro diversity and macro diversity are explained.
7.8.1
Soft Handover
Soft handover is performed between two cells belonging to different Node Bs but not necessarily to the same RNC. The source and target cell of the soft handover has the same frequency. In case of a circuit switched call, the terminal performs soft handovers at all times if the radio network environment has small cells.
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Fig. 42 The UE is moving from cell cite 1 to cell site 2. In the middle we have the soft handover window.
Principles of UMTS Terrestrial Radio Access (UTRA)
Figure 42 describes Principle of WCDMA Soft Handover:
Fig. 43 Principle of WCDMA Soft Handover
Soft handover is performed between two cells belonging to different Node Bs but not necessarily to the same RNC. The source and target cell of the soft handover has the same frequency. In case of a circuit switched call, the terminal performs soft handovers at all times if the radio network environment has small cells. Figure 43 describes Principle of WCDMA Softer Handover: zezenenu.und.lmm/cajaqara.en.slo
Fig. 44 Principle of WCDMA Softer Handover
In softer handover, the Node B transmits through one sector, but receives from both the sectors. In this case, the UE has active uplink radio connections with the network through two cells populating the same Node B.
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7.8.2
Hard / Inter-Frequency Handover
The UMTS hard handover is a ‘GSM-like’ handover performed between two WCDMA frequencies. In case of a hard handover, the connection through the old cell is cleared and the connection with the radio network continues through the new cell. Hard handover should be avoided if possible because it often results in increased interference. Figure 44 describes Principle of UMTS Hard Handover:
The UMTS hard handover is a ‘GSM-like’ handover performed between two WCDMA frequencies. In case of a hard handover, the connection through the old cell is cleared and the connection with the radio network continues through the new cell. Hard handover should be avoided if possible because it often results in increased interference. The hard handover performed if the Iur interface is not available. For example, between the RNCs coming from two manufacturers.
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Fig. 45 Principle of UMTS Hard Handover
Principles of UMTS Terrestrial Radio Access (UTRA)
Figure 3.45 illustrates Hard / Intra-Frequency Handover :
Fig. 46 Hard / Intra-Frequency Handover
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7.8.3
Intersystem Handover from GSM
The handover between GSM and UTRAN can be performed for a number of reasons, for example, to provide specific high bit rate services. The handover is possible because a dual mode UE receives the UTRAN neighbour cell parameters on GSM system information messages. The parameters that enable the UE to measure the neighbouring UTRA FDD cell are: downlink centre frequency, downlink bandwidth (currently only 5 MHz), downlink scrambling code, or scrambling code group for the CPICH, and reference time difference for the UTRA cell.
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Figure 46 illustrates Intersystem Handover from BSS to UTRAN:
The sequence of events in the intersystem handover to BSS to UTRAN is as follows: 1. 2. 3. 4.
5. 6.
The UE/MS creates a measurement report that the BSC evaluates to make the handover decision. The reservation messages are sent to the UTRAN if the BSC decides to hand over to a UTRA cell resource, The UTRAN acknowledges the resource reservation and provides a UTRAN handover command. The BSC sends the GSM intersystem handover command to the UE. In this command, a UMTS Handover to UTRAN command is included, which contains all the information needed to set up a connection to the UTRA cell. The message contains reference number to UTRA parameters not the real values to cater to a situation when the configuration information is more than a GSM message can handle. The UE completes the procedure of Handover to UTRAN by a sending complete message to the RNC. Finally, the RNC commands resources to be released by the BSC.
7.8.4
Hard / Inter-Frequency Handover
The UMTS hard handover is a ‘GSM-like’ handover performed between two WCDMA frequencies. In case of a hard handover, the connection through the old cell is cleared and the connection with the radio network continues through the new cell. Hard handover should be avoided if possible because it often results in increased interference.
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Fig. 47 Intersystem Handover from BSS to UTRAN
Principles of UMTS Terrestrial Radio Access (UTRA)
Figure 47 illustrates UMTS Hard Handover:
Fig. 48 Principle of UMTS Hard Handover
The hard handover performed if the Iur interface is not available. For example, between the RNCs coming from two manufacturers. Figure 48 illustrates Hard / Intra-Frequency Handover:
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Fig. 49 Hard / Intra-Frequency Handover
7.8.5
Inter-System Handover
The possible co-existence of the different radio accesses in the UMTS network, the UE should be able to fluently change the radio access technology when required. In order to cater this situation, the 3GPP Specifications identify the combination of UMTS and GSM as one source for inter-system handovers. The possibility to perform an inter-system handover is enabled in the UMTS by a special functioning mode, slotted mode. When the UE uses Uu interface in the slotted mode, the contents of the Uu interface frame are compressed in order to
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open a time window, through which the UE is able to peek and decode the GSM BCCH information. In addition, both the WCDMA RAN and GSM BSS must be able to send the identity information of the other on the BCCH and BCH channels to enable the UE to perform the decoding properly. Figure 3.49 illustrates UMTS/GSM Inter-System Handover:
7.8.6
Intersystem Handover from UTRAN
The handover between GSM and UTRAN can be performed for a number of reasons, for example, to provide specific high bit rate services. The handover is possible because a dual mode UE receives the UTRAN neighbour cell parameters on GSM system information messages. The parameters that enable the UE to measure the neighbouring UTRA FDD cell are: downlink centre frequency, downlink bandwidth (currently only 5 MHz), downlink scrambling code, or scrambling code group for the CPICH, and reference time difference for the UTRA cell.
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Fig. 50 UMTS/GSM Inter-System Handover
Principles of UMTS Terrestrial Radio Access (UTRA)
Figure 50 illustrates Intersystem Handover from UTRAN to BSS:
Fig. 51 Intersystem Handover from UTRAN to BSS
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The sequence of events in the intersystem handover to UTRAN to BSS is as follows: 1. 2. 3. 4. 5. 6.
Based on the measurement report including both UTRAN and BSS values the RNC makes the handover decision. Resource reservation messages are sent to the BSC. The BSC acknowledges the resource reservation and includes a GSM handover command. The RNC sends an Intersystem handover command message to the UE. In this message, the GSM Handover command is included. The UE switches to GSM RR protocol and sends the GSM handover access message to the BSC. The BSC finally initiates resource release with message to the UTRAN.
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7.8.7
Micro diversity
With reference to the soft handover and active set, the two terms that describe the handling of the multi path components are micro diversity and macro diversity. Micro diversity means the situation where the propagating multi path components are combined in the Node B. Figure 51 illustrates the Micro Diversity in Node B:
WCDMA utilizes the Multi path Propagation, which means that the Node B receiver is able to determine, differentiate and sum up several signals received from the radio path. The receiver used for Multi path Propagation is equipment called a RAKE receiver. In Multi path Propagation, a signal sent to the radio path is reflected from, for example, ground, water and buildings, and the sent signal id displayed as many copies at the receiving end. Each of the signal reaching the receiver at a different phase and time. The micro-diversity functionality at the Node B level combines (sums up) different signal paths received from one cell and, in case of sectored Node B, the outcomes from different sectors (softer handover).
7.8.8
Macro diversity
As the UE may use cells belonging to different Node Bs or even different RNCs, the macro-diversity functionality also exists on the RNC level. The figure depicting Macro Diversity in RNC presents a case in which the UE has a 3-cell active set in use and one of those cells is connected to another RNC. In the case, the Node Bs performs summing of the signal concerning their own radio paths. At the RNC level, the serving RNC evaluates the frames coming from the Node Bs and chooses the best signal to send towards the CN domains.
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Fig. 52 Micro Diversity in Node B
Principles of UMTS Terrestrial Radio Access (UTRA)
Figure 52 illustrates the Macro Diversity in RNC:
Fig. 53 Macro Diversity in RNC
In case of the soft and softer handovers, subjective call quality will be better when the final signal is constructed from several sources (multi path). In GSM, the subjective call quality depends on the transmission power used. In other words, the more power the better quality. zezenenu.und.lmm/cajaqara.en.slo
In UMTS, the terminals cannot use much power because if they do the transmission levels that are very high will start blocking the other users away. Therefore, the better way to gain better subjective call quality is to utilize the Multi Path Propagation. The soft and softer handovers consume radio access capacity because the UE is occupying more than one radio link connection in the Uu interface. The added capacity gained from the interference reduction is also bigger and as a result the system capacity is increased if soft and softer handovers are used.
7.9
Handover Decision-Making Mechanism
During the connection, the UE continuously measures some parameters such as signal strength, quality, and interference, concerning the neighboring cells and reports the status of these items to the network up to the RNC. These parameters are measured from the neighboring cells PICHs. The RNC checks whether the values indicated in the measurement reports trigger any criteria set. As the result of the trigger, the new Node B is added to the Active Set.
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Figure 53 illustartes the Handover Decision-Making Mechanism:
An Active Set is a list of cells, through which the UE has a connection to the network or through which the radio link set-up is established. The minimum size and maximum size of the Active Set is one cell and three cells respectively. The UE can have active radio connection with the network through three cells simultaneously.
7.10
Load Control in the RNC
The Radio Resource Management mechanisms Admission Control, Packet Scheduler and Load Control are important components when controlling the load in the UTRAN network. The purpose of load control is to optimize the capacity of a cell and prevent an overload situation to maintain the stability of the system. Load control consists of Admission Control (AC) algorithms, Packet Scheduler (PS) algorithms, and Load Control (LC), which updates the load status of the cell based on resource measurements and estimations provided by AC and PS.
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Fig. 54 Handover Decision-Making Mechanism
Principles of UMTS Terrestrial Radio Access (UTRA)
Figure 3.54 illustrates how the load control works logically in the RNC:
Fig. 55 Load control works logically in the RNC
If the system is overloaded, LC returns the system to normal load state in a fast and controlled way. LC can be divided into two functions: 1. 2.
Preventive control, which guards the system from overload. Overload control, which returns the system from an overload state to normal state.
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Interference is the main resource criteria for the CDMA system the following load control measures are practiced: 1. 2. 3.
UL total received wideband interference power DL total transmission power One RNC on cell basis periodically under.
RRM acts according to these measurements and parameters set by radio network planning.
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Figure 55 illustrates Capacity in the Uplink Limited by Interference:
In the downlink, the capacity is limited by the transmission power of the site. As more subscribers are added to a cell and as the subscribers move further away from the site towards the cell edge, the more power is needed to achieve a certain quality. At this point the capacity of a cell is filled in the downlink because the power/signal quality to assure a quality connection is not enough. In the uplink, the capacity is limited to amount of power or interference that is present in a cell. Therefore, the loading of a cell is based on the combination of these two directions. Figure 56 illustrates the Model of Cell Loading Against Traffic Profile:
Fig. 57 Model of Cell Loading Against Traffic Profile
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Fig. 56 Capacity in the Uplink Limited by Interference
Principles of UMTS Terrestrial Radio Access (UTRA)
The traffic in a cell can be categorized by priority, depending on the traffic type, for example, Conversational, Streaming, Interactive, and Background. The categories can be subdivided into Real Time (RT) and Non-Real Time (NRT) traffic. The figure above displayes a simple example of Release 99 implementation of real time and non-real time services. In practice, the real time traffic is given priority over non-real time traffic. The packets are scheduled to fill in the gaps between the real-time traffic and the load target. The traffic profile in UMTS is variable, therefore, overload values are used. As in displayed in the figure above, the system can handle moments of traffic peaks, but if the traffic is constantly above a certain limit, then certain load reduction measures, such as handovers, are taken. Figure 57 illustrates the relationship of AC, LC and PS, given a certain load:
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Fig. 58 How the AC, LC and PS work together
The parameters on the right-hand side specify the behavior of the load control.When the load on the cell is not much, the AC allocates real time bearers, and the PS is flexible with the packet load. When the load increases, no more real time bearers are allocated and the PS does not increase the load. If the load continues to grow, or at the most stay the same (remember, that the subscribers are still moving, which is affecting the power levels), then the LC takes actions, such as traffic reason handovers. The PS decreases the bit rate of the non-real time bearers in an effort to decrease load simultaneously.Under extreme conditions of the cell being overloaded, the LC may take actions, such as dropping the NRT bearers.
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8
Multi Carrier CDMA / UTRA / Time Division Synchronous CDMA
8.1
MC-CDMA and UTRA
UMTS as the 3G successor standard to GSM and Multi Carrier CDMA (MC-CDMA) as the 3G successor standard to IS-95 are compatible with each other. The compatibility is intended to facilitate the development of chipsets for UE that can Access the three major terrestrial IMT-2000 modes.
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MC-CDMA is downward-compatible with IS-95 B. The chip rate is 1.2288 Mchip/s and the carrier bandwidth is 1.25 MHz, which is same as in IS-95,. However, n carriers (where n = 1, 3, 6, 9, 12) can be commonly used for a user connection in DL transmissions. The data is de-multiplexed in this case on n carriers and can therefore be transmitted simultaneously.
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Figure 58 describes difference between MC-CDMA and UTRA:
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Fig. 59 Difference between MC-CDMA and UTRA
For UL, the DS-CDMA principle is used with a carrier transmission rate of n x 1.2288 Mchip/s and a bandwidth of n x 1.25 MHz. three MC-CDMA carriers, including two guard bands, each 625 kHz wide, can be used in a 5-MHz frequency band. Therefore, the frequency bands that were used for 2G systems can be replaced by MC-CDMA. MC-CDMA uses the same modulation method as UTRA (QPSK). The Orthogonal Walsh codes of variable length (comparable to UTRA) are used as channelization codes for spreading. Finally, the result is superimposed with a PN sequence to distinguish it from neighboring base stations. The PN sequence is identical to that used for IS-95 and explains the reason for compatibility between IS-95 and MC-CDMA. Only one sequence is required to distinguish between the base stations in IS-95 and MCCDMA because both systems Global Positioning System (GPS) have synchronized networks. The offset of the PN sequence is used for clear distinction of the neighboring base stations.
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The UTRA FDD and TDD networks are not synchronized similar to GSM networks.. As a result, they are not dependent on other systems, such as GPS. Consequently, different scrambling codes are needed to distinguish between neighboring base stations.
8.2
Time Division - Synchronous CDMA / Low Chip Rate Time Division Duplex Mode
From UMTS Release 4 on, a new RTT option, Time Division - Synchronous CDMA (TD-SCDMA) , which was originally developed by the Chinese SDO CATT, has been included into the UMTS standard:. TD-SCDMA is included as a second TDD option with a lower chip rate. Therefore, it is called Low Chip Rate TDD mode (LCR-TDD). 1. 2. 3. 4. 5. 6. 7. 8.
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Bandwidth: 1.6 MHz. Chip Rate: 1.28 Mchip/s. Spreading Factor: 1, 2, 4, 8, 16. Radio Frame Length: 10 ms, subdivided into two 5 ms sub-frames. Time Slot: 0.675 ms duration; 7 TS per sub-frame. Data Rate Variation: SF-variation; TS combining; change of modulation. A speed of maximum of 2 Mbit/s can be supported (theoretically). Modulation: QPSK (Quadrature Phase Shift Keying) and 8PSK (8 Phase Shift Keying).
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The key characteristics of LCR-TDD are:
Principles of UMTS Terrestrial Radio Access (UTRA)
Figure 59 illustartes the TD-SCDMA:
Fig. 60 TD-SCDMA zezenenu.und.lmm/cajaqara.en.slo
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9
High Speed Downlink Packet Access and High Speed Uplink Packet Access
9.1
Introduction to High Speed Downlink Packet Access
HSDPA is the first evolutionary step for the 3GPP WCDMA architecture and is specified in the Release 5 of the 3GPP standards. HSDPA enhances the peak download data rate from the current 384 kbps up to a theoretical maximum downloading peak rate of 14.4 Mbps. In RAS05 the maximum supported peak downloading rate is 1.8 Mbps.
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The introduction of HSDPA to the 3G network mainly affects the Radio Access Network, which consists of the Base Station (BTS), the RNC, and the UE. Figure 60 illustrates the basic functionality of HSDPA:
Fig. 61 The basic functionality of HSDPA
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HSDPA contains several technological enhancements. The increase in the downlink data rate and the actual cell throughput are due to three main factors; adaptive modulation and coding, fast scheduling, and fast retransmission. For HSDPA, the data rates used in the module are mainly peak data rates. The actual data rates experienced by the user will be lower because the radio channel used to transmit data to the subscribers is time shared between all HSDPA users in the cell. The channel conditions may also vary and cause more interference, which in turn decreases downloading speeds.
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Figure 3.61 explains the data rate in HSDPA:
In HSDPA, adaptive modulation and coding means that the modulation used, and the number of codes and code rate (factors that affect the downlink data rate) are optimized dynamically during the mobile connection according to the channel quality information (CQI) received from the UE. The modulation is Quadrature Phase Shift Keying (QPSK). In addition, the number of codes available is limited to five out of the maximum of 15 codes available, resulting in a maximum download peak data rate of 1.8 Mbps.
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Fig. 62 The data rate in HSDPA
Principles of UMTS Terrestrial Radio Access (UTRA)
Figure 62 illustrates the Adaptive Modulation in HSDPA:
Fig. 63 Adaptive Modulation in HSDPA
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Future RAN releases will introduce a new modulation method – 16 Quadrature Amplitude Modulation (16QAM), which is defined in the 3GPP Release5 specifications. The 16QAM modulation, together with a maximum of 15 codes, allows the maximum HSDPA downlink peak data rate of around 10 Mbps. Fast scheduling in HSDPA technological enhancements, includes a faster Transmission Time Interval (TTI) reduced from 10 ms to 2 ms and packet scheduling handled by the BTS. The third HSDPA technological enhancement, fast retransmission, results from the fact that data retransmissions are now primarily handled in the BTS in layer 1. The TCP layer and RLC layer retransmissions are still used when needed. In layer 1 retransmission, a process called Hybrid Automatic Retransmission Quest (HARQ) is used to transmit the correct information to the UE. In addition to the layer 1 retransmissions the BTS is also responsible for the Iu-b interface flow control.
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Figure 3.63 illustrates the Hybrid Automatic Retransmission Quest:
HSDPA also introduces new radio channels that include a transport channel, HSDSCH, and physical channels, HS-PDSCH, which is used to carry HS-DSCH, HSDPCCH for uplink control data purposes and HS-SCCH, which is used to carry downlink control information. The Iub-interface is also used more efficiently because the time-shared channel used to carry HSDPA data and also due to the fact that HSDPA does not support soft handover. Besides the capacity and data rate improvements, HSDPA requires only marginal investments to the current WCDMA network because it can be deployed using small upgrades and does not require a completely new network structure. Therefore, HSDPA protects the investments made to the network. HSDPA is also compatible with earlier RAN releases and enables the gradual introduction of the technology. All of these improvements allow operators to offer services at a lower cost per delivered bit.
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Fig. 64 Hybrid Automatic Retransmission Quest
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Figure 64 explain the new radio channels in HSDPA:
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9.2
Introduction to High Speed Uplink Packet Access
High Speed Uplink Packet Access (HSUPA) defines a new radio interface for the uplink communication. HSUPA was introduced in Release 6. The first standard was improved in December 2004, and the 3GPP Release 6 core specifications defining the enhanced uplink were completed in May 2005. HSUPA is also known as FDD Enhanced uplink or E-DCH. As with HSDPA, the aim with HSUPA has been to increase capacity and throughput while reducing delay. Following key features are introduced with HSUPA to achieve this:
4. 5.
A new dedicated uplink channel Enhanced Dedicated Channel (E-DCH) Introduction of HARQ (Hybrid Automatic Retransmission request) Fast Node B Scheduling in uplink - introduction of MAC-e/es (Page 16 HSUPA) Support of Macro diversity ( Soft Handover) Shorter TTI of 2 ms
Introduction of MAC-e in Node B and UE and of MAC-es in RNC and UE.The MAC-es/e sublayer was introduced to handle the E-DCH specific functions. On the UE side the MAC-e/es entity provides the HARQ functionality, multiplexing of multiple MAC-D PDUS into MAC-es and MAC-e PDUs and setting of the Transmissions Sequence Number (TSN). Furthermore the MAC-e/es entity is responsible for the selection of the E-TFC (Transport Format Combination) according to the scheduling information. The MAC-e in the Node B controls access to the E-DCH and is connected to MAC-es located in the s-RNC. That means MAC-e in the Node B performs the E-DCH Scheduling and the HARQ - functionality. Additionally the MAC-e demultiplexes the MAC-e PDUs to their corresponding MAC-d flows into MAC-es PDUs and forwards them to the s-RNC. Note that the soft combining for the possible multiple Radio Links of a Node B takes place in the Node B. The MAC-es entity in the s-RNC performs reordering functions and Macro Diversity Selection in case of soft handover with multiple Node Bs. Then it disassembles the MAC-es-PDUs to MAC-d PDUs and forwards them to MAC-d. Benefits of the HSUPA The user data rates, the delay properties, the cell throughput and the cell coverage are important properties that partly characterize the efficiency of the mobile network system. The HSUPA is designed to improve all these properties and thus enable improved user experience that brings added value for end users and network operators. It is estimated that the User Data rates are improved by 20 – 100 % depending on the network conditions. Round trip times as short as 50 milliseconds are to be attained. The cell throughput is estimated to improve by 20 – 50 %.
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1. 2. 3.
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The coverage gain is between 0.5 and 1.5 decibels. As with the HSDPA, the coding rate can be changed dynamically in order to adapt dynamically to the channel conditions. In the HSUPA, the half rate, three to- four ratio rate and four-to-four ratio coding rates are defined by the 3GPP specifications. The implementation of the HSUPA functionality requires changes in the layer 1 signalling between the User Equipment and the Base Transceiver Station. The new signalling must be able to handle the acknowledgements sent over the air interface, scheduling information and the actual retransmissions of the data packets. The introduction of the HSUPA will also cause certain changes in the Iub interface and in the Uu interface for layer 2 and 3 functionality. Figure 65 explain the Transmission in HSUPA:
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Fig. 66 Transmission in HSUPA
The retransmission concept in the HSUPA resembles that of the HSDPA case. The three layers of transmissions include retransmission over the air interface, RLC layer retransmission between the User Equipment and the Radio Network Controller, and the retransmission in the TCP layer between the User Equipment and the application server. In the HSUPA case, all the base stations that are in the soft handover mode will send acknowledgements independently.
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Figure 66 explain the retransmission concept in the HSUPA:
Unlike HSDPA, HSUPA remains based on a dedicated channel. The Enhanced Dedicated Channel (E-DCH) is introduced as a new transport channel for user data in the uplink direction. To support the E-DCH, two new physical channels in the uplink directions have been specified: E-DCH Dedicated Physical Data Channel (E-DPDCH) E-DCH Dedicated Physical Control Channel (E-DPCCH) The E-DCH Dedicated Physical Data Channel is used to carry uplink user data. The E-DCH Dedicated Physical Control Channel transmits control information for E-DPDCH including information to enable the Node B to decode the transmitted user data (Scheduling and Transport Format Related Information). E-DPDCH and E-DPCCH are transmitted simultaneously. In the downlink direction two new physical channels are introduced to perform scheduling tasks: E-DCH Absolute Grant Channel (E-AGCH) E-DCH Relative Grant Channel (E-RGCH) The E-AGCH and E-RGCH are used for the uplink Fast Scheduling mechanism. Another physical channel is introduced in the downlink direction to support the HARQ functionality: E-DCH HARQ Acknowledgement Indicator Channel (E-HICH) Similar to the HS-DPCCH in HSDPA in the uplink direction the E-HICH offers feedback about the received data from the Node B to the UE in form of ACK (Acknowledgement) or NACK (Negative Acknowledgement).
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Fig. 67 Retransmission concept in the HSUPA
Principles of UMTS Terrestrial Radio Access (UTRA)
Figure 67 explains the type of channels in HSUPA:
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Fig. 68 Type of channels in HSUPA
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Appendix
10.1
UMTS radio network planning
In this course module, we have been dealing with quite general information that is useful to everybody within the operator's technical organisation. In the remaining parts of this module, we will have a closer look at some important issues related to radio network planning.
10.1.1
Introduction to UMTS radio network planning
Major steps in all UMTS network planning will be in most part identical to current 2nd generation network planning. These steps are summarised as follows: 1. Basic network dimensioning
2. Site selection Because most new WCDMA operators are also 2nd generation PDC or GSM operators, the site selection will be done in co-operation with site acquisition and existing sites. 3. Detailed network planning More detailed WCDMA network planning will be done after preliminary site selection, including issues like coverage/capacity planning, propagation model tuning, parameter planning, and soft/softer handover overhead analysis and optimisation. Preliminary capacity simulations estimate around 250 - 300 Erlangs per cell using three sectors. This could be enhanced further by, for instance, using beam forming intelligent antennas or several scrambling codes (frequencies) within the same cell. Because actual capacity of a single cell is dependent from much larger variety of different, and changeable, factors and parameters than with current 2nd-generation systems, we call this soft capacity. 4. Network testing and tuning Interference level testing (intra-cell, inter-cell, etc.) and related power level tuning will play a major part in the process of trying to get maximum capacity from any WCDMA type of network.
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This will be in most parts similar to previous cellular networks, but the difference will be that the main traffic type for the next five years is estimated to be medium to high speed data, not low speed (8-16 kbit/s) speech. Hence, new packet switched services conveyed by the GPRS/packet core network will have an effect on dimensioning.
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10.1.2
Issues of UMTS planning compared with GSM planning
The frequency planning is a very important planning area in GSM networks. The frequency band available for GSM purposes is relatively limited and it must be used as efficiently as possible. As there is a limited amount of carriers available, the operator must repeat those frequently. The aim of frequency planning is to create and maintain suitable methods of how this frequency repeating can be done so that the same frequencies are not repeated too often and too close to each other. In other words, the frequency planning aims to maintain radio connection quality at an adequate level with limited resources. As a basic assumption, the WCDMA frequency re-use factor is 1, that is, every cell uses the same frequency. This has a remarkable effect on the radio network planning and the principles are completely different than in case of GSM. In GSM systems, interference is a bad obstacle, but in WCDMA systems a certain level of interference is actually required to have an optimally functioning UTRAN. However, when working with GSM and UMTS networks, the use of GSM for coverage provision, handovers and the direction of traffic to GSM vs. UMTS must be considered. zezenenu.und.lmm/cajaqara.en.slo
UMTS networks work in a multi-service environment, where the bit rates vary from around 8 kbit/s to (theoretically) 2 Mbit/s depending on the subscribers' activities. Furthermore, UMTS provides bearers based upon quality classes where traffic is asymmetric in the uplink and downlink directions.
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10.1.3
Basic difference between GSM and WCDMA
There are many obvious differences between the GSM and UMTS air interface. For the reasons of simplicity, we can say that there are two distinct categories of differences in UMTS: the multi-services to a subscriber and the air interface itself. The UMTS multi-service environment can support bit rates from 12.2 kbit/s to 2 Mbit/s, at variable rate (unlike the GSM fixed rate). In NSN's RAN 1 release the maximum bit rate is 384 kbit/s. The services in RAN 1 are divided to Real Time (RT) and Non-Real Time (NRT), each of these having a different quality class and different error ratios, BLER (Bit Loss Error Ratio), and BER (Bit Error Ratio). The delay sensitivity is from 100 ms to seconds. There is asymmetric traffic in the uplink and downlink traffic. As a result, more transmission capacity is needed.
In WCDMA, cell capacity is based upon load and neighbour cell interference. Also neighbouring cells using the same frequency, and therefore the concept of gain through soft handovers are introduced. The usage of soft handovers increases the load in a cell, but the overall effect is a gain since the interference is reduced. Also, in CDMA, fast power control commands are used to ensure high capacity. Very fast and accurate TX power control is required.
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In WCDMA the size of the cell actually changes. As more capacity (that is, more voice calls or higher data rates) is applied to a cell, the actual diameter will shrink. This phenomenon is thus referred to as cell breathing. Features are used in the Nokia solution to reduce its effects. In WCDMA, we also have several different physical channels, while as in GSM, we only have one (the timeslot).
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11
Exercises
Exercise 1 1. In UMTS, there are two methods used for transport through the air interface. The first is UMTS-FDD. What is the second one? TDD, Time Doubled Division CDD, Code Division Duplex TDD, Time Division Duplex CDD, Code Divided Data
Exercise 2 Which of the following is introduced in Rel 5 ? zezenenu.und.lmm/cajaqara.en.slo
HSUPA UMTS HSDPA EDGE
Exercise 3 Which release includes HSUPA? Rel 3 Rel 5 Rel 6 Rel 99
Exercise 4 Which statement best describes the phenomenon called cell breathing?
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When more capacity is used, the cell spreads in size. When more capacity is used, the cell shrinks in size. The cell will adjust its size in line with the furthest users. Cell breathing is the height of the cell, 2 - 3 km towards the atmosphere.
Exercise 5 Which statement is true of scrambling codes? To separate downlink physical channels in a cell.. To separate user data and signalling in the network. As security to check if the User Equipment (UE) is not stolen.
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To separate different cells in the downlink direction
Exercise 6 Which UMTS channel is NOT available at Physical Layer? BCCH CCPCH DPCH DPDCH
Exercise 7 What is the maximum data speed (Theoritical) in HSDPA? 2 Mb 14.4 Mb 8 Mb 10 Mb
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Exercise 8 What is the chip rate is MC-CDMA ? 3 Mcps 2 Mcps 1.228 Mcps 5 Mcps
Exercise 9 What is the bandwidth used in TD-SCDMA? 5 MHz 3.84 MHz zezenenu.und.lmm/cajaqara.en.slo
1.22 MHz 1.6 MHz
Exercise 10 Which statement is true for channelization? The lower the bit rate, the more data can be spread. Before spreading, an error-protection code needs to be added to the baseband data to ensure a safe path through the air interface. The channelisation code is added as part of the spreading function. The channelisation code depends on the spreading factor used. All of the above.
Exercise 11 Which modulation type is used in UMTS? GMSK
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QPSK 8PSK BPSK
Exercise 12 Which modulation type is used in HSDPA? 16QAM QPSK 8PSK BPSK
For which tasks is the RAKE receiver NOT responsible? (Choose two) Multipath Propagation Delay Listening to surrounding BTSs Channel coding Speech coding
Exercise 14 Which statement is true of Admission Control? The UEs handle resource allocation. The RNC makes the decision of resource allocation, based upon interference. The RNC will not limit the number of the users on a cell. As more users are allocated a code, the load on a cell remains the same.
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Exercise 13
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Exercise 15 Which statement is true when RNC is used to allocate codes? Each cell has a scrambling code that acts like a cell ID. Channelisation codes are dependent upon the subscribers' identity. Scrambling codes are generated randomly. Scrambling codes are used in channelisation.
Exercise 16 Which power control is used when a mobile phone is idle? Closed loop power control Outer loop power control zezenenu.und.lmm/cajaqara.en.slo
Internal loop power control Open loop power control
Exercise 17 Select the right handover type. 1. Soft 2. Softer 3. Hard 4. Inter-system 5. Not possible Sector 1 to Sector 2 (same Node B) _____ 2 Node B x to Node B y _____ 1 RNC to RNC with Iur interface _____ 1 RNC to RNC with no Iur interface _____ 3 UMTS-FDD to UMTS-TDD _____ 5 WCDMA to GSM _____ 4 WCDMA to IS-95 _____ 5
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Exercise 18 What is the difference between micro and macro diversity? There is no difference. Micro diversity is the combination of signals between the Node B and the UE, whereas macro diversity is the combination of signals from many Node Bs in the RNC. Macro diversity is the combination of signals between the Node B and the UE, whereas micro diversity is the combination of signals from many Node Bs in the RNC. Macro and micro diversity are UE-specific functions.
Exercise 19 What is the one difference between HSDPA and HSUPA ? zezenenu.und.lmm/cajaqara.en.slo
HSDPA supports Soft handover, HSUPA does not. HSDPA does not supports Soft handover, HSUPA does. Both of the support Soft Handover. None of the above
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11.1
Solutions
Exercise 1 (Solution) 1. In UMTS, there are two methods used for transport through the air interface. The first is UMTS-FDD. What is the second one? TDD, Time Doubled Division CDD, Code Division Duplex TDD, Time Division Duplex CDD, Code Divided Data
Exercise 2 (Solution) Which of the following is introduced in Rel 5 ? zezenenu.und.lmm/cajaqara.en.slo
HSUPA UMTS HSDPA EDGE
Exercise 3 (Solution) Which release includes HSUPA? Rel 3 Rel 5 Rel 6 Rel 99
Exercise 4 (Solution) Which statement best describes the phenomenon called cell breathing?
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When more capacity is used, the cell spreads in size. When more capacity is used, the cell shrinks in size. The cell will adjust its size in line with the furthest users. Cell breathing is the height of the cell, 2 - 3 km towards the atmosphere.
Exercise 5 (Solution) Which statement is true of scrambling codes? To separate downlink physical channels in a cell.. To separate user data and signalling in the network. As security to check if the User Equipment (UE) is not stolen.
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To separate different cells in the downlink direction
Exercise 6 (Solution) Which UMTS channel is NOT available at Physical Layer? BCCH CCPCH DPCH DPDCH
Exercise 7 (Solution) What is the maximum data speed (Theoritical) in HSDPA? 2 Mb 14.4 Mb 8 Mb 10 Mb
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Exercise 8 (Solution) What is the chip rate is MC-CDMA ? 3 Mcps 2 Mcps 1.228 Mcps 5 Mcps
Exercise 9 (Solution) What is the bandwidth used in TD-SCDMA? 5 MHz 3.84 MHz zezenenu.und.lmm/cajaqara.en.slo
1.22 MHz 1.6 MHz
Exercise 10 (Solution) Which statement is true for channelization? The lower the bit rate, the more data can be spread. Before spreading, an error-protection code needs to be added to the baseband data to ensure a safe path through the air interface. The channelisation code is added as part of the spreading function. The channelisation code depends on the spreading factor used. All of the above.
Exercise 11 (Solution) Which modulation type is used in UMTS? GMSK
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QPSK 8PSK BPSK
Exercise 12 (Solution) Which modulation type is used in HSDPA? 16QAM QPSK 8PSK BPSK
For which tasks is the RAKE receiver NOT responsible? (Choose two) Multipath Propagation Delay Listening to surrounding BTSs Channel coding Speech coding
Exercise 14 (Solution) Which statement is true of Admission Control? The UEs handle resource allocation. The RNC makes the decision of resource allocation, based upon interference. The RNC will not limit the number of the users on a cell. As more users are allocated a code, the load on a cell remains the same.
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Exercise 13 (Solution)
Principles of UMTS Terrestrial Radio Access (UTRA)
Exercise 15 (Solution) Which statement is true when RNC is used to allocate codes? Each cell has a scrambling code that acts like a cell ID. Channelisation codes are dependent upon the subscribers' identity. Scrambling codes are generated randomly. Scrambling codes are used in channelisation.
Exercise 16 (Solution) Which power control is used when a mobile phone is idle? Closed loop power control Outer loop power control zezenenu.und.lmm/cajaqara.en.slo
Internal loop power control Open loop power control
Exercise 17 (Solution) Select the right handover type. 1. Soft 2. Softer 3. Hard 4. Inter-system 5. Not possible Sector 1 to Sector 2 (same Node B) _____ 2 Node B x to Node B y _____ 1 RNC to RNC with Iur interface _____ 1 RNC to RNC with no Iur interface _____ 3 UMTS-FDD to UMTS-TDD _____ 5 WCDMA to GSM _____ 4 WCDMA to IS-95 _____ 5
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Exercise 18 (Solution) What is the difference between micro and macro diversity? There is no difference. Micro diversity is the combination of signals between the Node B and the UE, whereas macro diversity is the combination of signals from many Node Bs in the RNC. Macro diversity is the combination of signals between the Node B and the UE, whereas micro diversity is the combination of signals from many Node Bs in the RNC. Macro and micro diversity are UE-specific functions.
Exercise 19 (Solution) What is the one difference between HSDPA and HSUPA ? zezenenu.und.lmm/cajaqara.en.slo
HSDPA supports Soft handover, HSUPA does not. HSDPA does not supports Soft handover, HSUPA does. Both of the support Soft Handover. None of the above
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UMTS Identity and Traffic Management
Contents
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1
Module Objective.......................................................................................3
2 2.1
Databases in Traffic Management...........................................................4 Network Databases.....................................................................................4
3 3.1 3.2 3.3 3.4 3.5 3.6
Characteristics of the Bearer................................................................... 7 Identify the Bearer .......................................................................................7 Characteristic of a Network Bearer .............................................................8 Types and Configuration of Bearers........................................................... 9 Bearer Transmission in the Network .........................................................11 Managing the Bearer Through The Network ............................................ 12 Managing the Bearer over UTRAN........................................................... 13
4 4.1 4.2
Area Identifier .......................................................................................... 15 Hierarchy of GSM/UMTS Service Areas and Codes ................................ 15 User and User Equipment Identities......................................................... 19
5 5.1
Subscriber Identity ..................................................................................21 Subscriber Addressing and Identities....................................................... 21
6 6.1 6.2 6.3
Procedures...............................................................................................24 Initially Accessing the Network ................................................................. 24 Simplified Bearer Establishment for a Call ............................................... 25 IMSI Attach for an Existing Subscriber..................................................... 27
7
Radio Resource Control States, Mobility Management, and Connection Management................................................................ 29 RNC: RRC States and Location Information ............................................ 29 Mobility Management................................................................................ 33 Cellular Architecture..................................................................................34 Mobility Procedure - Location Updating.................................................... 36 Location Info Retrieval in the CS and PS Domains..................................42
7.1 7.2 7.3 7.4 7.5
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7.6 7.7 7.8 7.9
Management of the UTRAN Registration Areas....................................... 43 Paging the Subscriber...............................................................................43 Roaming in Another Network .................................................................... 44 Mobility Management Procedures.............................................................46
8 8.1
Session Management..............................................................................47 Initially Accessing the Network ................................................................. 47
9
The Session Management of Real Time and Non-Real Time Bearers are Handled Through the Network................................ 57 Managing a Real Time Bearer in Circuit-Switched Domain..................... 57 Managing a Non-Real Time Bearer in the Packet-Switched Domain......................................................................................................60
9.1 9.2
Communication Management................................................................ 67 Call Control for Circuit- Switched (Real Time) Calls .................................67 Generation and Collection of Charging Data ............................................ 69 Handling Emergency Calls ........................................................................70
11
Appendix.................................................................................................. 71
12 12.1
Exercises..................................................................................................73 Solutions....................................................................................................77 zezenenu.und.lmm/kucusiqa.en.slo
10 10.1 10.2 10.3
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1
Module Objective
The aim of this module is to give the student the conceptual knowledge needed for explaining how traffic management is visualized in a UMTS network. Topics to be covered in this module include understanding the network databases and the information stored within them. At an overview level, you we will look at the different management layers in the network. After completing the module, the participant should be able to: List and identify the databases used within the UMTS network. Identify the subscriber addressing information. Name the characteristics of a bearer. Describe how the connection moves with the subscriber when a bearer is in use. Explain Identities Related to Subscriber in UMTS. List the procedures used to maintain mobility management in the network. List the procedures done when the mobile gains access to the network. Identify how the network selection is made. Describe how the session management of real time and non-real time bearers are handled through the network. zezenenu.und.lmm/kucusiqa.en.slo
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2
Databases in Traffic Management
2.1
Network Databases
The databases are used to control UMTS network activities such as paging, channel set-up, and authentication. They are also used to store other information about the subscriber, such as rights to services, security data, and identification numbers.
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Figure 1 summarizes the databases that are found within a mobile network:
Fig. 1 Mobile Network Databases
Since the core network will not change dramatically in the first release of UMTS, the registers are similar to those in Global System for Mobile Communication (GSM) and General Packet Radio Service (GPRS).
2.1.1
Visitor Location Register
Visitor Location Register (VLR) database contains temporary copies of the active subscribers, who have performed a location update in its area. VLR is considered to be an integral part of the Serving Mobile Switching Center (MSC). The VLR maintains mobility management related procedures such as location update,
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location registration, paging, and security activities. A mobile phone is roaming in the supply area of an MSC, which is controlled by a VLR. When the Mobile Station (MS) enters the VLR supply area, it is automatically in a new location area. The MS starts the location update or registration process. It gets registered in the VLR, which also holds the information of the mobile phone’s current location. If the MS is in the supply area of the VLR for the first time, interaction with the HLR is required to retrieve data required for authentication and the subscription profile. If the location update request takes place within a VLR supply area, an interaction with the HLR is only required when the VLR does not have valid data to perform the authentication procedure. Given the subscriber profile in the VLR, the VLR is also involved in the call set-up process. It holds the relevant information for authorization. The VLR stores crucial data such as the: International Mobile Subscriber Identity (IMSI) Mobile Station International ISDN number (MSISDN) Temporary Mobile Station Identity (TMSI), if applicable Last known location area (LAI) zezenenu.und.lmm/kucusiqa.en.slo
2.1.2
Home Location Register
Home Location Register (HLR) contains permanent data of the subscribers. One subscriber can always be in only one HLR. The HLR is responsible for mobility management related procedures in both the circuit switched and packet switched domains. The circuit-switched network elements MSC and Gateway MSC (GMSC) are connected to the HLR through the interfaces C and D, while the packet-switched network elements Serving GPRS Support Node (SGSN) and Gateway GPRS Support Node (GGSN) are connected to it through the interfaces Gr and Gc. MSC and SGSN are serving the User Equipment (UE) locally. They have to interact with the HLR to retrieve information necessary for service provisioning. GMSC and GGSN require location information to route mobile terminated call to the serving MSC and SGSN.
2.1.3
Authentication Centre
Authentic Centre (AuC) is a database handling the Authentication Vectors. These vectors contain the parameters that the VLR uses for security activities performed over the Iu interface. AuC is connected only with the HLR through the non-standardized interface H. The HLR requests data for authentication and cipher setting from the AuC. The HLR can store this data and make it available to the VLR and SGSN on demand. The data delivered from the AuC is used for the following three functions:
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1. 2. 3.
Mutually authenticating the Subscriber Identity Module (SIM) card through IMSI and the serving Public Land Mobile Network (PLMN). Delivering a key to check the communication integrity over the radio path between the UE the Visited Public Land Mobile Network (VPLMN). Ciphering over the radio path between the user equipment and the Radio Network Controller (RNC).
2.1.4
Equipment Identity Register
Equipment Identify Register (EIR) maintains the security information related to the UE hardware. This optional database is used to verify the International Mobile Equipment Identity (IMEI) numbers. The EIR is organized in the following three lists: Black list - Holds IMEIs, which are forbidden in the PLMN Grey list - Holds IMEIs under supervision by law enforcement agencies White list - Holds IMEIs, which are allowed to access the PLMN
The Short Message Service Centre (SMSC) is an intermediate store for the received/sent short messages. Therefore, it has signaling connections with the VLR, GPRS Support Nodes, and Gateway/Interworking MSC. The Intelligent Network (IN) Service Control Point (SCP) nowadays has Intelligent Network Application Part (INAP) and/or Camel Application Part (CAP) connections towards the Core Network-Circuit Switched (CN-CS) domain elements. The CN-CS domain elements having the IN connection are called Service Switching Points (SSPs). In the packet-switched domain, the HLR is still a centralized source of information. However, two service nodes are used to supply the required Internet Protocol (IP) access information, the Domain Name Server (DNS) and Firewalls. The DNS is used for Access Point Name (APN) to GGSN IP address translation. The SGSN needs to find out which GGSN that supports access to this a specific access point. The role of the DNS is therefore to give the SGSN the IP address to the GGSN. After this, the GGSN is able to route the subscriber’s request further. The border between the corporate networks, public IP, and 3G Core Network-Packet Switch (CN-PS) domain is maintained by the GGSN which may use the RADIUS database for user authentication. Firewalls are used for security control of external network connections. Other nodes such as voice mail systems and application servers can also contain subscriber and network information.
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A mobile phone can be also classified as to be unknown in the EIR. The interface F connects the EIR with the VLR, while the Gf interface links it with the SGSN.
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3
Characteristics of the Bearer
3.1
Identify the Bearer
A bearer is similar to a tunnel that goes through the different network elements and is carried on the different network interfaces. Figure 2 describes the Network Bearer:
Fig. 2 Network Bearer
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An application, such as video, in a mobile has a point-to-point connection to a remote application, such as video, on another terminal. From the physical network's point of view, the UMTS Radio Access Network (UTRAN) must ensure that the bearer is maintained over the Air Interface and is correctly routed to the core network. The core network ensures that the bearer is connected into either the service platform, or the Internet, or an external network, or in the case of a voice/video call, onto the Public Switched Telephone Network (PSTN). In the case of the PSTN, the information/data in the bearer pipe must be converted to a form that is understood by the outside world.
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Figure 3 explains data and speech is routed through the bearer:
Fig. 3 Data and Speech Routing through the Bearer
Characteristic of a Network Bearer
If you think in terms of GSM, you probably consider the traffic channel to be the same as a bearer in the Air Interface. However, the bearer does not share all the characteristics of a traffic channel. For example, unlike the traffic channel, the bearer can carry different types of data such as speech and circuit-switched data. The fundamental difference between GSM and UMTS is that in UMTS, the bearer is flexible. The type of the bearer is reserved and the way it is routed through the network depends on the subscriber's service need. To better understand this concept, consider two examples. Example 1: Voice Traffic Suppose that voice data requires a data speed of 12.2 kb/s. Note: The bit rate depends on the speech coding method used for the voice data. To ensure quality, if we add error correction information/data, the total amount of data needed in the Air Interface is approximately 24 kb/s. For the interfaces within the radio access network (Iub, Iur) and towards the circuit switched-core network (Iu), the bit rate required is around 16-19 kb/s, including overhead. Therefore, you need a connection from the mobile to the Media Gateway that can support these bit rates. In addition, you have to take the delay factor into account. As subscribers you are not tolerant of delays in speech or video conversations.
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Example 2: Internet Connection Consider the example of connecting to the Internet using your mobile. Internet traffic is often burst and asymmetric because there is usually more to download than to upload. In addition, the delay factor is not as significant for Internet connection as for conversation and therefore, more variable bit rates can be tolerated. However, in this case the data may be very sensitive to errors as compared to voice transmission. From the preceding two examples, you can conclude that the network will allocate the bearer based upon the request of the subscriber's need. To be more precise, it is the RNC that makes the decision about the bearer allocation.
3.3
Types and Configuration of Bearers
As with all mobile systems, the largest bottlenecks in allocating resources to a mobile subscriber are in the Air Interface. This is the reason why the RNC is responsible for the bearer allocation. The Air Interface is limited in terms of the maximum amount of subscribers, the maximum data rates, the coverage area, and quality of data transmission. In UMTS, all of these factors are linked together. If you introduce more people to a cell, then the size and bit rate reduces. The UMTS specification defines four classifications of bearers. zezenenu.und.lmm/kucusiqa.en.slo
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Fig. 4 Different Air Interface Classifications of Bearers
Figure 5 illustrates typical data speeds needed for common 3G services:
Fig. 5 Typical Data Speeds Needed for Common 3G Services
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Figure 4 shows the different Air Interface classifications:
UMTS Identity and Traffic Management
It is necessary that the transmission and core networks must be capable of supporting the data speed different needs. Consequently, one of the important tasks for the network planners is to dimension the accurate capacity in the network beyond the Air Interface. For example, if a video call has to be made through the network. A dedicated traffic channel for the Air Interface must then be requested. The UE must also inform the network about the required bearer classification and data speed. It is then the RNC's responsibility to allocate an Air Interface channel and to establish the connections through to the core network.
3.4
Bearer Transmission in the Network
During transmission throughout the network, the bearer resides in a physical channel. On connection between the BTS and the RNC and towards the MSC/SGSN, a frame-structure protocol, typically ATM, is used. Figure 6 demonstrates this transmission through the use of pipes between elements in the network:
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Fig. 6 Transmission through the Network using Pipes
The Air Interface also has physical channels, which are used to carry signaling messages and data between the terminal and the network. The network elements ensure that the right data is moved from one pipe to another. In the Circuit Switched-Core Network (CS-CN) domain, there is always a dedicated circuit for the connection and it is only released at the end of the call.
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In the Packet Switched-Core Network (PS-CN), tunneling is used to make a virtual connection between IP network elements. Although tunneling ensures a semi-dedicated channel in an IP network, it is still not the same as having a dedicated circuit in the network. Basically, the tunnel enables a virtual circuit between the RNC through the SGSN, and towards the GGSN.
3.5
Managing the Bearer Through The Network
The UMTS network is responsible for establishing a flexible bearer for subscriber data transport between the Mobile Terminal (MT) and the external networks. In the bearer set-up phase, the Quality of Service (QoS) parameters must be known, so that the individual network elements within the UMTS network are able to set-up the bearer.
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Figure 7 explains the QoS management in the control plane:
Fig. 7 QoS Management in the Control Plane
To establish a bearer in accordance to the QoS requirements of the user’s circuit switched application, a peer-to-peer Bearer Service (BS) signaling between the MT, MSC, and GMSC takes place. In case of a packet-orientated service request, bearer related signaling and control information/data must be exchanged between the MT, SGSN, and GGSN. The peer-to-peer signaling is necessary, so that the affected network elements can determine the required QoS parameters for the end-to-end bearer. If one network element is not capable of establishing the bearer, a re-negotiation can be initiated to find an alternative bearer. However, re-negotiation is possible only if the subscriber’s application permits it, or if the UMTS PLMN is not capable of
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offering the requested service. If the UMTS BS manager uses the GPRS Tunneling Protocol (GTP) for QoS negotiation between each other. If BS manager agreed on the QoS parameters for the bearer, the UMTS BS manager of the CN informs the CN BS manager about the QoS parameters for the bearer between SGSN and GGSN. It is then the responsibility of the CN BS manager to negotiate on how to make the bearer available and which route to take between the SGSN and GGSN. If BS manager agreed on the QoS parameter at their level, they inform the Backbone Network Service (BB NS) manager about the set QoS parameter. Within the backbone, any transmission technology such as IP over ATM or IP over Frame Relay may be applied. Depending on the underlying transmission technology and signaling protocols used, the network elements must conduct signaling to step-by-step establish the bearer between SGSN and GGSN. A bearer also must be established between the MT and the SGSN. The RNC is responsible for the resource management within UTRAN. The RNC manages Radio Access Bearer (RAB). A RAB refers to one bearer/connection between an MT and a core network edge element such as SGSN or MSC.
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The RNC must establish the bearer on Uu, Iub, Iu, and, if required, on Iur. After determining the internally used QoS parameter from the QoS parameters set by the manager in the SGSN, it informs its Iu BS manager to negotiate and establish the bearer between itself and the SGSN. The RAB manager also informs the Radio BS manager about the required QoS parameter. The Radio BS manager then determines the radio QoS parameters. The physical parameters for the transmission through the radio interface, such as spreading codes, spreading factor, type of convolution coding, are then determined in the underlying UTRA physical BS manager. The whole process is conducted to establish a bearer on every physical link within the UMTS operator’s network, in accordance with the QoS required for the subscriber’s application. Bearers for signaling can also be negotiated. However, they are often made available during operation and maintenance.
3.6
Managing the Bearer over UTRAN
In UMTS there may be a number of connections between the core network and the mobile. As an example, a subscriber may have a video, voice, and Internet connection bearer open. This means that the subscriber will be using multiple bearers to support each service. As explained before, each of these connections is known as a RAB. The RABs for an individual subscriber are grouped together into a Radio Resource Control (RRC). RRC is a stack structure in which the RABs are located. Therefore, if you need to move the RRC, for example in the case of a handover from one BTS to another, then you need to move the whole RRC.
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Figure 8 shows how the different RABs are received by the RNC and combined together to form a single RRC connection:
The 3G specifications make provision for procedures that allow for the RAB to be added, modified, and removed in an RRC. This may be required if a subscriber needs an additional service, for example, downloading e-mail messages. To control the connection between the network and the mobile, a signaling protocol called RRC is used. By using the protocol, the network can carry messages that are required to set up, modify, and release RRC.
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Fig. 8 Relationship between the RAB and RRC in the UTRAN
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4
Area Identifier
4.1
Hierarchy of GSM/UMTS Service Areas and Codes
The GSM/UTMS service areas and codes have the following hierarchical levels:
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International GSM/UMTS Service Area - The international GSM/UMTS Service Area refers to the world-wide area where access to GSM or UMTS networks is possible. It is sub-divided into National Service Areas. National Service Area - The National Service Area is the area of a country or a region. It is identified by the Mobile Country Code (MCC) and the Country Code (CC) and is sub-divided into one or more PLMN Service Areas. Location Area (LA) - An LA is the most precise UE location information, which is stored in the circuit-switched domain in the VLR of UMTS. An LA is uniquely identified world-wide by its Location Area Identity (LAI). The LAI is composed of the MCC with 3 digits, the MNC with 2 or 3 digits, and the Location Area Code (LAC) with2 bytes. The LAC identifies an LA within a PLMN. The LAI is used as CN-CS Domain Identifier (Domain -Id). A CN Domain-Id is used within UTRAN to identify a CN-CS Domain Node for relocation purposes. Routing Area (RA) - An RA is a sub-set of LA. One LA may contain one or more RAs. The RA is the most precise UE information, which is stored in the PS-domain in the SGSN of UMTS. It is uniquely identified world-wide by the Routing Area Identity (RAI). The RA is sub-divided into the Cell Areas. The RAI is composed of the MCC, the MNC, the LAC, and the Routing Area Code (RAC), with 1 byte. The RAC identifies an RA uniquely within an LA. The RAI is used as CN-PS (Domain -Id). PLMN Service Area - A PLMN Service Area is the service area of a single PLMN. It is identified by the Mobile Network Code (MNC) and the Network Destination Code (NDC) and is sub-divided into one or more MSC and SGSN Service Areas. An MSC Service Area is served by a single MSC in the circuit-switched domain and SGSN Service Area is served by a single SGSN in the PS-domain. MSC and SGSN service areas are on the same hierarchical level. The MSCs and SGSNs have their own identities or addresses for signaling and user data transfer. The MSC Service Area is sub-divided into one or more LA and the SGSN Service Area is sub-divided into one or more RA. Cell Area - The Cell Area means the area, where the UE is located. It is the most precise data to be stored in the PLMN, in the RNC. The Cell is uniquely identified world-wide by the Cell Global Identity (CGI).
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The CGI is composed of the MCC, the MNC, the LAC, and the Cell Identity (CI) with 2 bytes. The CI identifies a cell uniquely within an LA. LAI, RAI, and CGI are very important LAIs. Many other areas are also specified in UMTS.
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Figure 9 illustrates hierarchy of GSM/UMTS Service Areas / Codes:
Fig. 9 Hierarchy of GSM/UMTS Service Areas / Codes
The smallest entity within the radio network is known as a cell, which is served by a base station. The operating size of the CI can change geographically depending on the parameters used. The cells are grouped together geographically into LA, RA, and URA.
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Figure 10 illustrates the structure of the network:
Fig. 10 UMTS Cellular Architecture
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The reasoning behind the structure of the network is to make UMTS backward compatible with GSM and GPRS. The location areas are used in the CS Domain as the routing areas are used in the PS Domain. A single cell can belong to both a LA and RA and this information is used by the core network for routing information to the Radio Access Network (RAN). In GSM, two separate connections are made for circuit-switched and packet-switched data. In UMTS, there is a single connection that can carry multiple bearers. Therefore, to reduce the excessive amount of signaling that may occur, an URA is introduced to monitor the location of a subscriber in the RAN. Note that, one MSC can have many LAs, but an LA cannot be used across MSCs. An RA can be used cross Base Station Controllers (BSCs), but not MSCs. A cell cannot belong to different LA or RA, they must be unique. A cell can belong to more than one URA.
4.1.1
Network Location Areas
The LA is used in the CS Domain. The LA consists minimum of one cell and the maximum limit is all the cells under one VLR. Therefore, the maximum size of one LA could be the same as the VLR area. In the location update procedure the location of the UE is updated in the VLR with LA accuracy. This information is needed in case of a mobile terminated call. The VLR pages the desired UE from the location area it has performed the latest location update on. The LA does not have any other hardware bindings other than the VLR. For example, one RNC may have several LAs or an LA may cover several RNCs.
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LAI is unique number throughout the world. LAI is composed of the following parts: LAI = MCC + MNC + LA Code Where: MCC = Mobile Country Code (3 digits) MNC = Mobile Network Code (2 digits) LA code = A number identifying the LA. To globally separate cells from each other, the identity is expanded and called CGI. CGI is composed of the following parts and in this case it is called: CGI = MCC + MNC + LA Code + CI Where: MCC = Mobile Country Code (3 digits) MNC = Mobile Network Code (2 digits) LA code = A number identifying the LA. Cl= Cell number within the network
Network Routing Areas
An RA is the area where the UE may move without performing the routing area update in the PS Domain. On the other hand, the RA is kind of a subset of LA. One LA may have several RAs within it, but not vice versa. In addition, one RA cannot belong to two LAs. The reason RA and LA co-exist is the possibility to have a UE supporting either circuit or packet traffic, but not both. At the core network side, the VLR and the SGSN can have a common optional interface, Gs, through which these nodes may change location information. For example, if the UE performs a location update, the VLR may inform SGSN through the Gs interface that the UE should also perform routing area update in order to guarantee packet traffic.
4.1.3
UTRAN Registration Areas
The reason for having the CIs, Las, and RAs is to ensure compatibility to GSM and GPRS networks. In 3G/UMTS, an additional grouping of cells URA is introduced. As the RNC has greater mobility management functions, and it controls handovers between RNCs, it must identify which cells belong to which RNC. As a subscriber moves into the geographical range of the RNCs serving area, the subscriber is allocated into the serving URA. Only when the subscriber moves from the control or supervision of one RNC to another, the information has to be updated.
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When transmitting the paging signal, the RNC can limit the paging to the URA area, therefore, reducing the amount of signalling in the network. SGSN uses the RNC address when routing packets for a designated user. With URA, it is also possible to create more accurate demographic areas within the network, which means that a URA can be defined more flexibly than LA or RA with respect to the subscriber location and the pattern of movement. Figure 11 illustrates the RNC and URA architecture in the network:
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Fig. 11 RNC and URA Architecture in the Network
The MSC and the VLR still use the LA-based method for mobility management functions for circuit-switched operations, such as CS call set-up. For GPRS, the 3G-SGSN still works on the basis of RAs. Therefore, the only new entities are the URA and UTRAN positioning services. Unlike in GSM, the RNC can handle inter-RNC handovers through the Iur interface. In GSM, the MSC is always responsible for inter-BSC handovers. As UMTS networks are designed to work with different types of core network, the only way that the network can identify the cells belonging to specific RNC is based on the use of URA.
4.2
User and User Equipment Identities
The user and user equipment identities are as follows: IMSI MSISDN IMEI The IMSI is the quasi-permanent subscriber identity in GSM/UMTS. The IMSI is composed of the MCC with 3 digits, MNC with 2 digits, Mobile Subscriber Identification Number (MSIN) with 10 digits. The total length of the IMSI is 15 digits.
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The MSISDN is an ISDN telephone number of the GSM subscriber. The MS international ISDN numbers are allocated from the CCITT Recommendation E.164 numbering plan, see also CCITT Recommendation E.213. The number consists of the CC with 1 to 3 digits of the country in which the MS is registered, followed by the National mobile number consists of NDC with 2 to 3 digits and Subscriber Number (SN). The maximum length of the MSISDN is 15 digits. For GSM applications, a NDC is allocated to each GSM PLMN. In some countries more than one NDC may be required for each GSM PLMN. The IMEI is used as the Mobile Equipment identity. The IMEI can be checked at the start of a connection by the EIR. The IMEI with 15 digits consists of a Type Approval Code (TAC) with 6 digits, the Final Assembly Code (FAC) with 2 digits, which identifies the place of manufacture or final assembly, the serial number with 6 digits and a spare digit.
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Figure 12 illustrates the User and UE Identities:
Fig. 12 User and UE Identities
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5
Subscriber Identity
5.1
Subscriber Addressing and Identities
Each subscriber has to be uniquely identified. As in 2G networks, in UMTS unique addressing codes are used to identify the subscriber. Figure 13 illustrates the identities used to identify the subscriber and the location where the information is stored:
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Fig. 13 IMSI and MSISDN Addresses in the Network
The unique identity for the mobile subscriber is the IMSI, which is the same as in GSM. The IMSI is composed of three parts as shown below: IMSI = MCC + MNC + MSIN Where: MCC = Mobile Country Code (3 digits) MNC = Mobile Network Code (2 digits) MSN = Mobile Subscriber Identity Number (normally 10 digits) This number is stored in the SIM card or USIM. The MSISDN is used for service separation. One subscriber may have several services provisioned and activated, using one IMSI. For example, the mobile user may have one MSISDN number for speech service and another MSISDN number for facsimile.
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The MSISDN is composed of three parts as shown below: MSISDN = CC + NDC + SN Where: CC = Country Code (1 to 3 digits) NDC = National Destination Code (1 to 3 digits) SN = Subscriber Number This number format follows the E.164 numbering specification. Often, the MSISDN number is called directory number or subscriber number. It is important to avoid the unique identity, which is the IMSI or International Mobile User Identity (IMUI),being transferred in a non-ciphered mode due to security reasons. For the same purpose, the UMTS system uses TMSI number, which is also called Temporary Mobile User Identity (TMUI). Due to security reasons, the packet-switched domain of the core network also allocates similar temporary identities called Packet Temporary Mobile Subscriber Identity (P-TMSI).
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Figure 14 explains temporary information stored in the UMTS network:
Fig. 14 Temporary Information Stored In the UMTS Network
TMSI/TMUI and P-TMSI are random-format numbers with limited validity time and validity area. The TMSI/TMUI numbers are allocated by the VLR and are valid until the UE performs the next location update procedure. The TMSI/TMUI may change earlier and this pace of change is controlled by the network. The P-TMSI
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is allocated by the SGSN and is valid for the SGSN area. The P-TMSI is changed when the UE performs routing area update. IMEI is the number, which uniquely identifies the hardware of the user equipment. Aseparate register called EIR handles these identities. The network may or may not ask the UE to identify itself with the IMEI number for every transaction or for the cases defined by the network operator occasionally. Figure 15 shows terminal equipment security:
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Fig. 15 Ensuring Terminal Equipment Security
As explained before, all the IMEI numbers are handled in three lists, white grey, and black, within the core network. White listed IMEI numbers are normal identities, which do not have any troubles. The grey listed IMEI numbers are under observation, and every time a UE with grey listed IMEI is used, the network produces an observation report about the transaction. If the accessed UE is on the black list, the network rejects the transaction, except in case of an emergency call. There are several other addresses that are used. For example, Mobile Subscriber Roaming Number (MSRN), which is used for call routing purposes. The format of the MSRN is the same as of MSISDN. This means that the MSRN consists of three parts, CC, NDC, and SN and follows the E.164 numbering specification. The MSRN is used during a call set-up between the network and a subscriber on another MSC.
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6
Procedures
There are procedures used to obtain a bearer through the network and a terminal is also capable of determining one network from another. Each country has its own MCC and each operator within a country has a unique MNC. This information is broadcasted by every cell in the network. Therefore, when the mobile is activated, it is able to distinguish between operators by checking this information. Through co-operation of the operators, the frequencies and codes used and shared in inter-boarder areas are selected for network planning to reduce conflict.
6.1
Initially Accessing the Network
When the mobile is switched on, it starts the network selection procedure. The mobile is aware of the possible frequencies that are available in UMTS and all the possible codes that are used by the cells.
Once the scanning process is over, the mobile selects its home network as the first choice. The information for the home network is on the SIM. If the home network is not present, then it can choose a preferred network, which is usually set by the home network operator. If the preferred network is not available, the mobile randomly selects another network that provides the adequate signal level. The procedure of network selection is usually performed automatically, but it can also be made manually.
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First, the mobile checks the last frequency and code used to identify the cell to check if it is still valid. If the cell cannot be found, the mobile starts applying each code to each possible frequency in an attempt to detect a signal that indicates the presence of a cell.
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Figure 16 shows the initial network access when the mobile is switched on:
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Fig. 16 Initial Network Access: Mobile Switched On
On the selection of the network, the mobile will request a location update or IMSI attach for its position. The RNC will then request for the location update. If the home network is present the first time, the update is made. For the update, the information on the subscriber is copied to the serving VLR for the MSC area and the current information on the subscriber is updated to the HLR. The subscriber is also be registered into the current URA.
6.2
Simplified Bearer Establishment for a Call
The UMTS BS manager in the SGSN requests a bearer set-up between the MT and itself. It sends a RAB Assignment request to the radio resource control unit RNC. The bearer control messages are exchanged between SGSN and RNC with Radio Access Network Application Protocol (RANAP) messages. First, the Iu-PS bearer between SGSN and RNC is set up in accordance to the required quality of service parameter by following the UMTS specific RAB Assignment Request message. Currently, the Iu-PS bearer between SGSN an RNC t is an AAL5 virtual channel. Then, an Iu-b bearer between Node B and RNC is established. This bearer is an AAL2 virtual channel and later on will be used for user data transport.
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A signaling connection already exists between the UE and the RNC. This connection is used to send the Radio Set-up Bearer message to the UE. The UE is informed about the physical layer characteristics, MAC layer characteristics, for example puncturing, and data rate, RNC modus, for example, acknowledged/unacknowledged mode. Then, the Radio Link Reconfiguration message informs the Node B among other Node Bs about the physical and MAC layer characteristics of the Uu interface transmission. The Node B confirms this message by returning a Radio Link Configuration Complete message. Next, the UE confirms the Radio Bearer Set-up message with the Radio Bearer Set-up Complete message. Now the bearer between the UE and the RNC exists. Finally, The RNC returns the RAB Assignment Complete message to the SGSN, with which the UMTS bearer between UE and SGSN is established. Note the bearer establishment within UTRAN is very complex and allows a wide range of different options.
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Figure 17 illustrates a simplified example of RAB establishment:
Fig. 17 RAB Establishment (Simplified)
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6.3
IMSI Attach for an Existing Subscriber
If the subscriber is already registered in the network and is still registered in the same VLR, the information is updated. Also the HLR is informed of the new information. Figure 18 shows the how the information about the subscriber is moved between two VLRs:
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Fig. 18 Moving the Subscriber Information Between VLRs
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Assume that the mobile has moved between two VLR areas while being switched off. The sequence of events will be as follows: When the subscriber switches on the mobile again, a location update request will be transmitted to the new VLR. Then the authentication and IMSI information is copied between the old and the new VLR. Similar set of events will take place between the UE and the SGSN in case of a routing area update. The authentication is performed. After a successful authentication , the HLR is updated with the new location information, after which the HLR sends the subscriber information to the new VLR . The old VLR is cancelled the old VLR. Finally, an acknowledge message is sent to the mobile, together with the TMSI/TMUI number. The packet core domain is also updated with the new location information.
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Moreover, the RNC constantly keeps track of all the connected subscribers' current URAs.
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7
Radio Resource Control States, Mobility Management, and Connection Management
7.1
RNC: RRC States and Location Information
For the exchange of any information between the UE and its Serving RNC, UE location information must be stored in this RNC. There are two basic modes of RRC Connectivity are as follows: 1. 2.
RRC Idle RRC Connected
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In the RRC Idle mode no UE location information are stored in UTRAN. The UE location information is only stored in CN and the UE is identified by NAS identifier, for example, IMSI, TMSI, and P-TMSI. No exchange of signaling information is possible. Before any signaling information can be exchanged and Radio Bearer can be established, the UE has to establish a RRC connection. This transition can only be initiated by the UE and can be triggered by the network with a paging request. The UTRAN Connected mode is entered when the RRC connection is established. In the RRC Connected mode, UTRAN stores UE location information and signaling connection between the UE and UTRAN exists. The four different States that exist in the RRC Connected mode are as follows: 1. 2. 3. 4.
Cell_DCH Cell_FACH Cell_PCH Cell_PCH
In the Cell_DCH state, a Dedicated Channel is allocated to the UE. The UEs cell is known in the Serving RNC. Handover is used to track the movement of the UE. In case of low activity, theRNC can decide to change from the Cell_DCH to the Cell_FACH state In the Cell_FACH state, no dedicated resources are allocated to the UE. Common channels are used for transmitting signaling messages and small amounts of user data. The UE location is known on cell level. If there is higher load, a transition to the Cell_DCH is performed. If there is no activity, a transit to the Cell_PCH is possible.
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In the Cell_PCH state, the UE is still known on cell level, Cell Updates are performed, but it can only be reached through Paging. The UE battery consumption is less than in the Cell_FACH due to Discontinuous Reception (DRX) functionality. If a Cell Update time counter exceeds a threshold, a transition to the URA_PCH through the Cell_FACH is performed. In the URA_PCH state, similar to the Cell_PCH state, but the UE is only known on URA level. Only the URA updates are performed to reduce the Uu signaling load. The following four methods are used to store the location information: UTRAN Registration Area (URA) UMTS Mobility Management (UMM) CN domain: CS and PS Service States UMTS Session Management States
The URA is a set of cells, specified by the network operator. The UE location is stored in the Serving RNC on cell or URA level. A Packet UE is tracked at the URA level when no data are actively transferred, but the probability of data transfer is high. In case of network side packet data delivery, a UE registered at URA level must be paged by UTRAN. The URA is an UTRAN internal area and is not visible outside UTRAN. There may not be any relation between URA and LA or RA. URA updating is a radio network procedure. Figure 19 shows the four states of RRC and Location Information:
Fig. 19 Four States of RRC and Location Infomation
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1. 2. 3. 4.
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The task of the UMM is used keep track of the UEs location. Different UMTS CN network elements store location information. In the CS Domain, the VLR stores location information on level of the LA. In the Packet Switched (PS) Domain, the SGSN stores location information on level of the RA. In the HLR, the actual location of the UE is stored on basis of the MSC area, which is the VLR address or the SGSN area, which is the SGSN address. Location Update Procedures (LUP) and Routing Update Procedures (RUP) are triggered by the UE to inform the CN about changes of the UEs location. In the integrated UMTS CN architecture, the CN consists of a CS and a PS service domain. The main PS and CS service states are as follows: 1. 2. 3.
CS or PS Detached Cs or PS Idle CS or PS Connected
In the CS or PS Detached state, the UE is not reachable by the network for CS or PS services. No LA or RA updates are initiated by the UE.
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In the CS or PS Idle state, the he UE is reachable by Paging for CS or PS Services. LA or RA updates are initiated by the UE periodically and at LA or RA change. In the CS or PS Connected state, a UE – CN signaling connection for CS or PS services is established. The UE initiates no LA updates; RA updates when the RA changes, which means there is no periodic RA Update. The transition between the states are performed as follows: 1. 2.
Between the Detach state and Connected state - Through the UE Attach or Detach procedures Between the Idle and Connected state - Through the Signaling Connection Establishment or Release procedures
From the Idle to Detach state through the UE Detach procedure Figure 20 shows the CS and PS service states in CN domain:
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A UMTS PS subscription contains the subscription of one or more Packet Data Protocol (PDP) addresses. Each PDP address is described by one or more PDP contexts in the UE, SGSN, and GGSN. Every PDP context exists independently in one of two PDP states. The PDP state indicates whether packet data transfer is enabled for a specific PDP address or not. The two PDP states are as follows: 1. 2.
Inactive state Active state
The Inactive state implies that the data service for a certain PDP address of the subscriber is not activated. In the inactive state, the PDP context contains no routing information and no packet data can be transmitted. If the GGSN receive Mobile-terminated Packet Data Units (PDUs) in an Inactive state, the Network-Requested PDP Context Activation procedure may be initiated if allowed for that PDP address. Otherwise, the PDUs may be discarded. The UE initiates the transition from Inactive to Active state by initiating the PDP Context Activation procedure. In the Active State, the PDP context for the PDP address in use is activated in the UE, SGSN, and GGSN. Routing information for transmission of packets exist between the UE and GGSN. The Active state is permitted only if the UMM is PS-Idle or PS-Connected. An Active PDP context for an UE moves to Inactive when the Deactivation procedure is initiated. Figure 21 shows the UMTS PS subscription and different PDP states:
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Fig. 20 CS and PS Service States in CN Domain
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Fig. 21 UMTS PS subscription and PDP States
7.2
Mobility Management
As the user terminals are not fixed to certain positions, the network must keep track of the location of the mobile. The system must at least be able to know the geographical area in which the subscriber is located. As in GSM networks, UMTS has a cellular architecture that allows the network to identify the subscriber. Therefore, the network maintains information about the location of a subscriber, and the procedures are specified to allow a constant updating of the databases as the subscriber moves around the network, and also from one network to another.
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Figure 22 illustrates the role of the HLR as the centralized database:
Fig. 22 Role of the HLR as the Centralized Database
The HLR is the central database that stores information on the subscriber, such as the IMSI and MSISDN. The HLR also stores information about the serving MSC and SGSN of the subscriber. In addition, the HLR stores information on the subscriber's service profile. In other words, the record of the different services, for example, teleservices, supplementary, and packet services, that the subscriber can or cannot use. Therefore, if the network needs to locate the subscriber in case of a mobile terminated call, or if the network needs to check if the subscriber is valid, then all requests are sent to the HLR.
7.3
Cellular Architecture
7.3.1
Location Based Information Services
Another characteristic of a 3G/UMTS network is that it is possible to determine the accurate position of the subscriber by using the UTRAN positioning service. Unlike the URA, LA, and RA that are used for controlling mobility management or the subscriber location for call set-up, the future for UTRAN positioning service is
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for the provisioning of services that are based upon the exact location of the subscriber. For example, emergency calls, viewing maps, and locating the nearest doctor. The aim of these services is to be able to locate the subscriber within a 50 - 70 m range. There are different techniques that can be used, such as Global Positioning System (GPS). However, this technique may have limitations due to line of sight, indoor coverage, and even political reasons. There are other techniques that use the triangulation between base stations to measure the delay in signals. Figure 23 illustrates the different service possibilities:
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Fig. 23 Service Possibilities
When location updating is active, the mobile is constantly informing the network of its current location. This information can then be accessed by different types of service applications. For example, if an emergency call is made, the mobile's location can be given to the police or ambulance services. Not that the subscriber can enable the location updating with the exception of law enforcement.
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7.4
Mobility Procedure - Location Updating
As the network maintains three layers of information on the subscriber's location, LA, RA, and URA, there are multiple procedures used to track the movement of the subscriber. The following are three basic types of location update procedures: 1. 2. 3.
Location registration (power on / cell attach) Movement between area Periodic update
In a GSM network, the BSC did not perform any mobility management function; instead the mobile contacted the core networks directly to inform about a change in location.
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In UMTS, the situation is different as the RNC not only keeps information about the subscribers and the URA they are in, but also updates location in the core network.
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Figure 24 shows the location update generic procedures and the corresponding information in the Network:
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Fig. 24 Location Update Generic Procedures and Information in the Network
As the RNC receives a location updating message, it takes responsibility for informing the core network. The RNC updates its own information about the subscriber within the URA and informs the SGSN and VLR, respectively, if the routing area or location area has also changed. The reason for updating a location is that the VLR and SGSN databases of the network are only temporary. Depending on the parameters that the operator use, the information is only stored for a certain time. If there are no updates, it is assumed that the information is old. Therefore, avoid storing a large amount of useless data in the network, the information is removed.
7.4.1
Location Area Based Procedures
Location registration or IMSI attach takes place when a UE is turned on and informs the VLR that it is now back in service to receive the calls. The network then sends the UE two numbers that are stored in the USIM or SIM card of the
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UE. These two numbers are the current LAI and the TMSI. The network sends the LAI through the control channels of the air interface. The TMSI, temporary identity, which regularly changes, is used for security purposes, so that the IMSI of a subscriber does not have to be transmitted over the air interface. Every time the mobile receives data through the control channels, it reads the LAI and compares it with the LAI stored in its USIM card. A generic location update is performed if they are different. The mobile starts the location update process by accessing the MSC or VLR that sent the location data.
Periodic location update is carried out when the network does not receive any location update request from the mobile in a specified time. This kind of situation is created when a mobile is switched on but no traffic is carried and the mobile is only reading and measuring the information sent by the network. If the subscriber is moving within a single location area, the MS does not need to send the location update request. A timer controls the periodic updates and the operator of the VLR sets the timer value. The network broadcasts this timer value so that a UE knows the periodic location update timer values. The location registration procedure is similar for both CS and PS Domains. In case of PS Domain, the MSCs or VLRs are replaced with SGSNs. When the VLR or SGSN is changed, the new VLR or SGSN sends information about this change to the HLR. The HLR responds by sending the subscriber information to the VLR or SGSN. Any earlier location information of the subscriber present in the HLR is cancelled.
7.4.2
IMSI Attach/Detach in the CS Domain
In the CS Domain, the UE may have the following two states: 1. 2.
Attached Detached
In the attached state, the UE is able to handle transactions and is active in the network. The UE continuously analyses its radio environment for LAC and cell identities being visible. When the UE is switched off or detached, it stores the latest radio environment information into its memory and informs the network that it is now being switched off. The VLR stores this state change and does not try to reach the UE for mobile terminated transaction. When the UE is switched on again, it first checks whether
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A channel request message sent contains the subscriber identity, which can be the IMSI or TMSI, and the LAI stored in the USIM card. When the target MSC or VLR receives the request, it reads the old LAI, which identifies the MSC or VLR that has served the mobile up to this point. A signaling connection is established between the two MSCs or VLRs and the subscriber's IMSI is transferred from the old MSC to the new MSC. Using this IMSI, the new MSC requests the subscriber data from the HLR and then updates the VLR and HLR after successful authentication.
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the radio environment matches to the one it has in its memory. If the radio environment matches, the UE informs the VLR that it is now attached again and able to handle transactions. If the radio environment does not match, the UE performs a location area update.
7.4.3
Routing Area Update in the PS Domain
As a procedure, the routing area update is very similar to the location update and serves the same purpose. Periodic routing area update is used for checking that a UE that has not performed any routing area updates for a period is still reachable. The UE performs a cell update and cell reselection when it changes cell within a routing area in Ready mode. This could be compared to a handover in UMTS or GSM for PS connections. Cell update and routing area updates halt possible reception or sending of data. In such cases, there is a possibility of buffering data in the Serving SGSN. Figure 25 illustrates the routing area update:
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Fig. 25 Routing Area Update
When the UE changes cells between the different routing areas, it performs a routing area update. The two types of routing area updates as follows: 1.
Intra-SGSN routing area update - One SGSN can manage many routing areas. If the new routing area is managed by the same SGSN as the old one, an intra-SGSN routing area update is performed.
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Inter-SGSN routing area update - If the new routing area is managed by a different SGSN, an inter-SGSN routing area update is performed. The old SGSN then forwards user packets to the new SGSN.
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2.
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7.4.4
Cell Attach/Detach
In the core network packet domain, the MM-state changes during the PS connection. The MM-state mostly depends on the activity of the connection. This means that when there are packets to send or receive, the MM-state of the connection is MM-connected. When there is nothing to transmit, the MM-state of the connection is MM-idle. The MM-detached state has the same meaning in both the CN domains. Figure 26 describes the mobility management states in PS Domain:
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Fig. 26 Mobility Management State Diagram in Packet Domain
In order to utilize the 3G network resources, such as radio bandwidth effectively, the MM-state management is not enough for the PS traffic. In PS traffic, the traffic delivered can be presented as occasional packet bursts. Between these bursts, the connection is not used, which leads to a situation where it is reasonable to cut the connection through the network in order to make the network resources available for other active connections. The method to suppress the packet connection, but at the same time retain the necessary information in both ends of the connection is called cell attach / detach.
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7.4.5
GPRS Evolution to UMTS
If you are familiar with GPRS, figure 25, which shows the different states may seem confusing. In UMTS, the RNC has different RRC states depending on the traffic situation. Therefore, the two states are from the point of view of the UE and the SGSN. From the point of view of SGSN, it is in MM-connected state when there is a packet attach or received message. Signaling may be opened to the RNC, but the MM-connected state is only used when there is actual traffic.
7.5
Location Info Retrieval in the CS and PS Domains
In case of mobile terminated transaction, the Gateway MSC, which is the first MSC to realize that the transaction must be terminated to the network to which the called subscriber belongs to, performs the location info retrieval procedure. The procedure starts when a MSC requests routing information for the called subscriber from the HLR. The HLR checks its database and finds out the destination MSC or VLR where the called subscriber has performed the location update. The HLR then asks the destination VLR to provide MSRN for call path connection purposes. The VLR responds by giving a MSRN, which the HLR forwards to the requesting MSC. Now the MSC can start the activities for call path connection towards the target MSC or VLR. When the call path is established up to the MSC or VLR, the called subscriber can be paged. In case of the PS domain: The procedure starts when the GGSN requests routing information for the called packet data subscriber from the HLR. The HLR checks its database and finds out the latest SGSN where the subscriber has performed the routing area update. The address of this SGSN is submitted to the GGSN for the data connection establishment. Now the GGSN has address information, with which it is able to establish the GTP tunnel between itself and the SGSN. When the GTP tunnel is established up to the SGSN, the paging of the called subscriber can be started.
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In case of the CS Domain :
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7.6
Management of the UTRAN Registration Areas
In UMTS, the RNC can handle simultaneous CS and PS connections to the subscriber. Both domains use the LA and RA respectively to track the subscriber's location. The RNC must track the URA in which the subscriber is. In networks where the RNCs are connected through Iur interfaces as opposed to the MSC controlling handovers, the subscribers drift through the radio network passing from one RNC to another. Therefore, the serving RNC must identify in which URA a subscriber is located when it receives traffic for itself in a circuit switched connection.
7.7
Paging the Subscriber
From the HLR, the network is able to determine area or routing area where the subscriber is located. The network, for example, MSC will contact the MSC or SGSN serving that area and request contact to the mobile. The VLR or SGSN will then send a paging message, which contains the ID of the subscriber on a dedicated channel in the air interface. A mobile in idle mode is always listening to this channel. zezenenu.und.lmm/kucusiqa.en.slo
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Fig. 27 Paging in the Network
If the mobile is able to detect that the network is trying to contact it, the mobile will request access to the network to gain a signaling channel and determine what the network is asking for, for example, set up a call or receive the SMS. In GSM, the VLR or SGSN asks every cell in a certain location area to send the same paging message. In UMTS, if the subscriber is known to be located in a certain URA, the RNC can intelligently page for the subscriber in the URA, therefore, reducing the signaling in the network.
7.8
Roaming in Another Network
When a subscriber is in a foreign network, the procedures are the same. When the subscriber registers in the visiting network, it will in turn contact the home network. A part of the IMSI code specifies the home network. If the two operators have a roaming agreement and the subscriber is valid, the subscriber information is copied into the serving VLR of the MSC and the information on the subscriber is stored in the HLR. Every VLR in the world has a unique address. As a subscriber moves from one network to another, the location updating proceeds as normal. The HLR is always informed of the unique VLR, in which the subscriber was last seen.
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Figure 27 illustrates paging in the network:
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Figure 28 illustrates roaming in another network:
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Fig. 28 Roaming in Another Network
If a subscriber is roaming in another network and the network needs to contact the subscriber to receive a video call, the location of the subscriber is checked from the HLR. The HLR will then contact the serving MSC to check if the subscriber is still located in the VLR. This is called the HLR request. Then, the information is returned to the MSC and a call is routed to the foreign MSC to begin the paging process. Even if the calling subscriber is located in the foreign network, the call still has to be initially placed back to the home MSC.
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7.9
Mobility Management Procedures
There are several different mobility management procedures. Following is a short list of UMTS specified procedures: Paging (CS) Paging (PS) Location update (CS) Cell attach/detach (PS) IMSI attach/detach (CS) Routing area update (PS) UE identity checking (CS/PS) Ciphering procedure (CS/PS) Location registration (CS and PS) Authentication procedure (CS/PS)
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Location info retrieval (CS and PS) UE hardware (IMEI) checking (CS/PS)
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8
Session Management
In the previous topic we looked at the mobility management and how the network keeps track of the location of the subscriber and the procedures it performs. In this topic we wil look at how the mobile is able to access the network and to obtain a bearer. We will also cover two simplified cases of how real time and non-real time bearers are set up in the network. There are procedures used to obtain a bearer through the network and terminal is also capable of determining one network from another. Each country has its own MCC and each operator within a country has a unique MNC. This information is broadcasted by every cell in the network. Therefore, when the mobile is activated, it is able to distinguish between operators by checking this information. Through co-operation of the operators, the frequencies and codes used and shared in inter-boarder areas are selected for network planning to reduce conflict.
8.1
Initially Accessing the Network
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When the mobile is switched on, it starts the network selection procedure. The mobile is aware of the possible frequencies that are available in UMTS and all the possible codes that are used by the cells. First, the mobile checks the last frequency and code used to identify the cell, to check if it is still valid. If the cell cannot be found, the mobile starts applying each code to each possible frequency in an attempt to detect a signal that indicates the presence of a cell. Once the scanning process is over, the mobile selects its home network as the first choice. The information of this is on the SIM. If the home network is not present, then it can choose a preferred network, which is usually set by the home network operator. If the preferred network is not available, the mobile randomly selects another network that provides the adequate signal level. The procedure of network selection is usually performed automatically, but it can also be made manually.
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Figure 29 shows the initial network access when the mobile is switched on:
Fig. 29 Initial Network Access: Mobile Switched On
On the selection of the network, the mobile will request a location update or IMSI attach for its position. The RNC will then request for the location update. If the home network is present the first time, the update is made. For the update, the information on the subscriber is copied to the serving VLR for the MSC area and the current information on the subscriber is updated to the HLR. The subscriber is also registered into the current URA.
8.1.1
IMSI Attach for an Existing Subscriber
If the subscriber is already registered in the network and is still registered in the same VLR, the information is updated. In addition, the HLR is informed of the new information.
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Figure 30 shows the how the information about the subscriber is moved between the two VLRs:
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Fig. 30 The Subscriber Information being transfered between VLRs
If the mobile has moved between to VLR areas while being switched off. The sequence of events will be as follows: 1. 2.
3. 4.
5. 6.
When the subscriber switches on the mobile again, a location update request will be transmitted to the new VLR . Then the authentication and IMSI information is copied between the old and the new VLR . Similar set of events will take place between the UE and the SGSN in case of a routing area update. The authentication is performed. After a successful authentication, the HLR is updated with the new location information, after which the HLR sends the subscriber information to the new VLR . The old VLR is cancelled.. Finally, an acknowledge message is sent to the mobile, together with the TMSI/TMUI number. The packet core domain is also updated with the new location information.
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Moreover, the RNC is constantly keeping track of all the connected subscribers's current URAs.
8.1.2
IMSI Attach when Roaming
The procedure for updating the VLR or SGSN when the subscriber is in a visiting network is the same as for a subscriber in the home network. If the two operators have a dedicated signaling link, then information is copied into the visiting network. The HLR is updated with information on the unique VLR or SGSN address where the subscriber is located.
8.1.3
Requesting for a Dedicated Bearer
When the mobile does not have a RRC to the network, it is known to be in the idle mode. For a service, a bearer is required. Therefore, when the subscriber requests a service, such as a video call or Internet connection, the mobile needs to make a request to the network. In the air interface there is a special physical channel that is used to receive request messages from the mobile, namely the Random Access Channel (RACH). Depending on the type of channel that the subscriber is interested in, the network attempts to secure a bearer. zezenenu.und.lmm/kucusiqa.en.slo
Figure 31 shows a mobile requesting a bearer from the network:
Fig. 31 Requesting a Bearer from the Network
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8.1.4
Gaining Access Without Interfering with Other Mobiles
When a mobile attempts to gain access to the network, it is not aware of the power level to use. Therefore, it estimates an appropriate level. Then the mobile sends a short burst of information, which includes a random sequence to the random access channel. When the network receives the request, the mobile re-transmits the random part of the initial burst on a separate channel. If the mobile detects this signal, it assumes that the network has acknowledged. If not, the mobile re-transmits again using more power. This process continues until the power level set by the network is reached or the network responds. Then, the network transmits information about the channel that the mobile can use on a different channel, provided a channel is available.
8.1.5
Access Security in UMTS
In UMTS, requirements for access security are not changed. It is required that end users of the system are authenticated, for example, the identity of each subscriber is verified because subscriber will not want to pay for calls that are made by a cheating impostor. zezenenu.und.lmm/kucusiqa.en.slo
The confidentiality of the voice calls and the transmitted user data is protected in radio access network. Therefore, the subscriber can choose the parties to communicate with. The subscribers also want the assurance that the confidentiality protection is applied; therefore, visibility of applied security mechanisms and privacy about the whereabout of the subscriber is required. An average person does not care about being tracable, but if persistent tracking would cause irritation. Similarly, exact information about location of certain people can be useful, for example, burglars. Privacy of the subscriber data is a critical issue when data is transferred through the network. Note that in this context, privacy and confidentiality are largely synonymous. Availability of the UMTS access is clearly important for a subscriber who is paying for it. For Network operators, reliability of the network functionality is important; therefore, they prefer to control the core network to ensure effective functionality. Network functionality is guaranteed by integrity of all radio network signaling. It is also ensured that all control messages are created by authorized elements of the network. Integrity checking protects against any manipulation of a message, for example, insertion, deletion, or substitution. An important method of providing security for network operators and subscribers is cryptography. Cryptography consists various techniques, which have roots in the science and art of secret writing. It is sometimes useful to make communication deliberately incomprehensive, for example, to use ciphering or, encryption, which is the most effective way to protect communications against malicious purposes.
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Figure 32 illustrates the UMTS security features:
Fig. 32 Network Authentication
8.1.6
UMTS Security Features
The most important security features in the access security of UMTS as follows: Mutual authentication of the user and the network Use of temporary identities Radio access network encryption Protection of signalling integrity inside UTRAN Note that publicly available cryptographic algorithms are used for encryption and integrity protection. Algorithms for mutual authentication are operator-specific.
8.1.7
Mutual Authentication
There are three entities involved in the authentication mechanism of the UMTS system. The three entities are as follows: 1. 2. 3.
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Home network Serving Network SN Terminal, which is USIM in a smart card
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The SN checks the identity of the subscriber as in GSM by a technique called challenge-and-response. , A new feature in UMTS is that the terminal checks that the SN is authorized by the home network and the mobile is connected to a legitimate network. The security is based on the Quintet, UMTS authentication vector, which is temporary authentication and key agreement data that enables a VLR or SGSN to engage in UMTS AKA with a particular user. A quintet consists of five elements as follows: 1. 2. 3. 4. 5.
A Network Challenge Random Access Number (RAND) An Expected User Response (XRES) A Cipher Key (CK) An Integrity Key (IK) A Network Authentication Token (AUTN)
The cornerstone of the authentication mechanism is a master key, K, which is shared between the USIM of the subscriber and the home network database. This is a permanent secret with the length of 128 bits. The key, K, is never transferred out from the two locations and the subscriber has no knowledge of the master key.
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At the same time, with mutual authentication, keys for encryption and integrity checking are derived. These are temporary keys with the same length of 128 bits. New keys are derived from the permanent key, K, during every authentication event. It is a basic principle in cryptography to limit the use of permanent keys to minimum and instead derive temporary keys from it for protection of bulk data. In the Authentication and Key Agreement (AKA) mechanism, the authentication procedure is started after the user is identified in the serving network. The identification occurs when the identity of the user, which can be the permanent identity, IMSI, or temporary identity, TMSI, is transmitted to VLR or SGSN. Then, the VLR and SGSN send an authentication data request to the AuC in the home network. The AuC contains master keys of the users and based on the knowledge of IMSI the AuC is able to generate authentication vectors for the user. The generation process contains executions of several cryptographic algorithms. The generated vectors are sent back to VLR or SGSN in the authentication data response. These control messages are carried on the MAP protocol.
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Figure 33 illustrates the generation process of authentication data request and authentication data response:
In the serving network, one authentication vector is needed for each authentication instance, for example, for each run of the authentication procedure. In other words, the potentially long distance signaling between SN and the AuC is not needed for every authentication event and the authentication events can be performed independently without the user actions after the initial registration. The VLR or SGSN can obtain new authentication vectors from AuC before the number of stored vectors runs out. The serving network, VLR or SGSN sends a user authentication request to the terminal. This message contains two parameters from the authentication vector, called RAND and AUTN. These parameters are transferred into the USIM that exists inside a tamper-resistant environment, for example, in the UMTS IC card (UICC). The USIM contains the master key, K, and uses it with the parameters RAND and AUTN as inputs for carrying out a computation that resembles the generation of authentication vectors in AuC. This process also contains executions of several algorithms similar to the corresponding AuC computation. As the result of the computation, USIM is able to verify whether the parameter AUTN was indeed generated in AuC and the computed parameter RES is sent back to VLR or SGSN in the user authentication response. Now, the VLR or SGSN is able to compare user response RES with the expected response XRES, which is part of the authentication vector. In case the responses match, authentication ends positively.
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Fig. 33 Authentication Data Request and Authentication Data Response
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Figure 34 shows the process of user authentication request and user authentication response:
Fig. 34 User Authentication Request and User Authentication Response
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The keys for radio access network encryption and integrity protection, CK and IK, are created as a by-product in the authentication process. These temporary keys are included in the authentication vector and are transferred to the VLR or SGSN. These keys are later transferred further into the RNC in the radio access network when the encryption and integrity protection start. Simultaneously, the USIM is also able to compute CK and IK after it has obtained RAND and verified it through AUTN. The temporary keys are subsequently transferred from USIM to the mobile equipment where the encryption and integrity protection algorithms are implemented. The Sequence Number (SQN) is a counter. There are two SQNMS and SQNHE respectively to support network authentication. The sequence number SQNHE is an individual counter for each user and the sequence number SQNMS denotes the highest sequence number the USIM has accepted.
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Figure 35 shows ciphering in UMTS/UTRAN:
Fig. 35 Ciphering in UMTS/UTRAN
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9
The Session Management of Real Time and Non-Real Time Bearers are Handled Through the Network
9.1
Managing a Real Time Bearer in Circuit-Switched Domain
At the first stage of any mobile originated action, a signaling channel needs to set up between the mobile and the RNC. This channel is used to verify the USIM, to identify the subscriber, to find out what the subscriber needs, and to perform the authentication procedures. The sequence of events for allocating the real time bearer is as follows:
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1. 2. 3. 4.
5.
6. 7. 8.
9.
The mobile requests a connection. The RNC instructs a BTS to reserve a signaling channel and through a common channel, which all mobiles in the area can share. The RNC informs the mobile about the channel to use. The mobile can use the signaling channel to communicate with the RNC and inform the RNC about the service or bearer requirements. If the mobile only wants to perform signaling, the dedicated channel already available will be sufficient for location update. If the subscriber wants a QoS assured service, for example, voice, the RNC forwards the call set-up message to the CS-CN. Depending on how the network is configured, the identity of the subscriber is checked before any bearer set-up proceeds. These transactions are usually performed not by using the subscribers IMSI, but by the TMSI. If TMSI is not available, then the IMSI is used. The network checks if the subscriber is allowed to use the service. It is also possible that the user equipment can be crosschecked to ensure that it is valid. In case of a call, the RNC informs the CS-CN or MSC that a traffic channel is needed. The MSC responds to the RNC with information about the bearer it should provide . In return, the RNC allocates the correct bearer service to mobile in the radio network. Once the connection is made, the RNC informs the MSC that the connection is complete and the transaction can start . The system knows when a voice or video call is required, as a result, MSC or Media Gateway (MGW) also understand where the end point should be. When the subscriber wants to call to another mobile, the procedure will be the same as in GSM, where the HLR enquiry is sent from the MSC or VLR .
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10. The HLR requests the MSRN from the target VLR. 11. The HLR informs the requesting MSC of the MSRN of the target subscriber. 12. The serving MSC contacts the target MSC to make the final connection to the subscriber. 13. The target MSC pages the called party and as the VLR only knows the location area of the subscriber, all the cells in the target LA are requested to send a paging message. Then, the mobile answers by requesting a signaling channel. If the call terminates in a UMTS network, a similar bearer assignment procedure will happen as described in steps 1 to 8 above. The set-up procedure for the target subscriber starts with the allocation of a bearer for a signalling channel. The subscriber identity is checked and a bearer for the traffic channel is allocated. Once the radio access bearer is in place, the RNC will respond with a confirmation of the set-up. Now, the two parties can start the conversation. This process enables UMTS to be added to an existing GSM network. In case of services such as, video, the core network will have a direct connection through an Asynchronous Transmission Mode (ATM) network or through a server that supports video streaming.
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Figure 36 shows a simplified UMTS originated - GSM terminated call set-up case:
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Fig. 36 Simplified UMTS Originated – GSM Terminated Call Set-Up
Figure 36 shows that specifications are based on the GSM procedures as much as possible. The summary of the steps in the figure 36 is as follows: 1. 2. 3. 4. 5.
A radio resource connection request for a signalling channel is requested. The RNC sets up the radio link between the base station and itself. The downlink RRC set-up Uplink RRC set-up complete messages. Call set-up message sent to the MSC or VLR. Security procedures are also performed.
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6.
7.
8. 9.
Bearer assignment request is created. The bearer parameters are defined and a binding identification number is allocated. Binding ID is used to combine the control information with user data for a certain connection. Radio access bearer set-up and radio link modification is performed. With the inputs from the MSC or VLR concerning the bearer, the RNC allocates an appropriate RAB in the air interface. The radio link between the BTS and the RNC is also modified in accordance with the bearer needs. The RNC informs the MSC or VLR that the bearer has been assigned. In steps 9 to 16, the CS-CN is common for UMTS and GSM, the call set-up procedures within the CN are the same, including HLR enquiry and MSRN allocation. For calls terminating in a UMTS network, a bearer and a radio link in the terminating side should be allocated in a similar way as in the originating side. GSM Evolution in the Nokia Solution.
The MGW for 3G-MSC (3G-IWU) also has to convert the ATM connection into PCM to make it compatible with the MSC. The Iu interfaces offer more service possibilities than the A-interface. Therefore, MGW also supports these services. Unlike in GSM, the voice transcoders, which are based upon Adaptive Multi-Rate (AMR) codecs are located in the Media Gateway. It is stated in the 3GPP Specifications that the transcoding function also logically belongs to the core network and is the most logical solution, as it allows cost-efficient transmission.
9.2
Managing a Non-Real Time Bearer in the Packet-Switched Domain
As the CS management is based upon GSM, the management of PS bearers is based upon GPRS. The sequence of events in the process of context activation as shown in Figure 37 are as follows: 1. The mobile first requests a signaling channel from the network. 2. In step 2 and 3, the RNC is not yet aware of the service required by the subscriber; therefore, it allocates a dedicated signaling channel and informs the mobile about the channel to use. An acknowledgement is also sent from the mobile. 4. The mobile requests a bearer. This request is for both, Access Point Name (APN) and the IP address. If the field is empty, then a dynamic IP address needs to be allocated. The APN is a symbolic name for a network interface in the GGSN. The interface leads to an external packet network. One GGSN can have several different access points to different networks.
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The function of the MSC is the same as in GSM. The new element MGW for 3G-MSC is responsible for converting the Iu (UMTS) messages to be compatible with the MSC (A-interface). The effect is that the MSC recognizes and treats UMTS calls in a similar way as the GSM calls.
UMTS Identity and Traffic Management
5. The SGSN checks the subscription data. Earlier, when the subscriber made a routing area update, the SGSN received the subscriber information from the HLR. In addition, security information for authentication and encryption is stored in the SGSN; therefore, it is possible to authenticate the UE or USIM. The IMEI checking may also be performed. If IMEI checking is performed, the EIR in HLR is interrogated. 6. In step 6 and 7, the requested GGSN is obtained and the request for context creation is sent to it. The SGSN gets the GGSN IP address from the DNS . The DNS finds the correct GGSN IP address based on APN. 8. The SGSN now sends a message to the GGSN. The request includes the APN and the proposed Tunnel Identification (TID). TID consists of the IMSI number and the Network Service Access Point Identifier (NSAPI). NSAPI is used as a reference number of the PDP context.
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The GGSN now selects the access point it will. The APN is associated with the external network the subscriber wants to use. It is a physical or logical interface in the GGSN. The access point is similar to the default gateway defined for a normal IP-subnetwork. It is a point outside the subnetwork. For the UE, the access point is its default gateway. In case of a dynamic address, the GGSN or an external network element can issue the IP address. The external element can be a Dynamic Host Configuration Protocol (DHCP) server, which issues dynamic addressing information. Alternatively, the external element can be a Remote Access Dial In User Service (RADIUS) server. The primary function of RADIUS is user authentication. 9. The GGSN sends a back to the 3G-SGSN, which includes the given IP address, TID confirmation, and a charging ID. 10. The 3G-SGSN sends a bearer assignment request, doing, to the RNC. 11. The RNC modifies the radio link and sets up the bearer over the air interface. 12. The RNC sends a message to 3G-SGSN to notify that the bearer assignment is completed. 13. Finally, the 3G-SGSN sends an message to the UE. The 3G-SGSN is now ready to route user traffic between the user equipment and the GGSN.
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Figure 37 shows PDP context activation:
Fig. 37 PDP Context Activation
A very important concept of the PS session management is PDP context The PDP context is used for two purposes, for PDP address allocation to the user and to make a logical connection with the required or desired QoS level through the 3G network. The PDP context is an entity that defines all required information for the UE – network connection establishment. From the session management (SM) point of view, the PDP context has the following two states: 1.
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2.
Inactive
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In SM active state, the network has routing information available and it is possible to transfer data between the UE and the network. In addition, the UE location information is updated in the PDP context. The inactive state means that the packet data services related to a certain PDP address are not active. The network does not have any routing information available for that PDP address, therefore, it is not possible to transfer any data. the PDP context information is not updated when the location of the UE changes.
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Figure 38 shows how the different PDP context procedures are used in different session management states:
Fig. 38 PDP Context States
One allocated PDP address may have many PDP contexts and one PDP context always has one QoS class or QoS profile. This makes it possible to have many packet data connections with each of them having a different QoS simultaneously. The UE can be used for software downloading and web browsing at the same time. As the network connection is established, packets of data in the PDU are transferred through the network by using different types of protocols. Between the mobile and the RNC, the packet data protocol is used. Between the RNC, 3G-SGSN, and the GGSN the packet of Internet data is transferred in the GTP.
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Figure 39 illustrates the GTP tunnel:
Fig. 39 The GTP Tunnel
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The user data packets are carried from RNC to GGSN through 3G-SGSN in containers. When a packet from an external packet network arrives at the GGSN, it is inserted into a container and sent to the SGSN. The container is then opened and packed into a new container towards the RNC. The stream of containers from RNC to the GGSN is transparent to the user. It seems as if the subscriber is connected directly through a router to an external network, or to an application. In data communications, this type of virtual stream of containers is called a tunnel. The SGSN and RNC perform tunnelling of user packets.
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Figure 40 illustrates the process of the deactivating the PDP context and quitting the connection:
Although the connection may remain active for some time, the mobile may deactivate the PDP context. The summary of the steps in the Figure 40 is as follows: 1. 2. 3.
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Steps 1 and 2 - A request is sent from the mobile, through the RNC to the 3G-SGSN to release the resources. Steps 3 and 4 - Once the mobile is deactivated, the radio resources are then released. Step 5. Finally, the RNC sends an acknowledgement to the 3G-SGSN.
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Fig. 40 Subscriber Quitting the Connection
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10
Communication Management
A UMTS network is a platform, which provides the best solution to the operators to in turn provide a varied amount of services. The applications of the subscriber applications and control components placed upon the bearer. Therefore, communication management in UMTS is all about managing mobility, security, and charging of a bearer. The role of communication management is to route the bearer to the high application layers, manage the connection through mobility management, handle the bearer security, and charge for the session. Figure 41 illustrates the services and control of the services that sit upon the physical connection:
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Fig. 41 Functions of Communication Management
The communication management requires the services of the lower layers, as the lower layers maintain the bearer.
10.1
Call Control for Circuit- Switched (Real Time) Calls
Call control describes the functions required for incoming and outgoing call handling within a switch at a high-level. The switch should perform three activities before a call can be connected. The activities are number analysis, routing, and charging. Call control can functionally be divided into three phases, which the call attempt must pass in order to perform through a connection.
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Number analysis is a collection of rules for handling the incoming calls.. Number analysis investigates both the calling and called numbers and makes decisions based on the rules defined. Number analysis is performed both in call control Phase I and Phase II. In Phase I, the switch checks whether the called number is reasonable and if any restriction, such as, call barring needs to be applied with the calling number.
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Figure 42 shows the call control principles:
Fig. 42 Call Control Principles
In call control Phase II, the system concentrates on the called number. The nature of the call is investigated to check if the call is international or national and if there is any routing rule defined for the called number. In addition, the system checks if the call requires any inter-working equipment, such as, a modem, to be connected and if the call is chargeable. The statistics for the call is also initiated in this phase. As a successful result of call control Phase II, the system knows where the call attempt should be routed. When the correct destination for the call is known, the system starts to set up channel(s) or bandwidth towards the desired destination by using an ISUP signaling protocol. During the call, the switch stores statistical information about the call and its connection and collects charging information if the call is chargeable. When the call is finished, call control Phase III handles the release of all the resources related to the call.
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10.2
Generation and Collection of Charging Data
The 3GPP Specifications give a detailed list of requirements for the type of Charging Data Record (CDR) to collect. The Charging Gateway, MSC, HLR and many elements within the service platform generate CDRs, which describe different events in the network. An event can be a call, SMS, data usage, location update, or any different type of network activity. Operators select what causes a CDR to be generated. The CDRs are transferred to the Billing Centre where the information is collected and priced. Figure 43 shows the collection of charging data:
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Fig. 43 Collection of Charging Data
As part of the evolution from GSM or GPRS towards UMTS, the amount of information contained in the CDR is increased to include details of the service quality and the network elements used. In addition, the UMTS Specifications describe features that allow the subscriber to view more information on the cost of a service. This network feature is called Advice of Charge (AoC) and is a supplementary service, which provides the subscriber with the details of the service cost immediately.
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10.3
Handling Emergency Calls
In UMTS and in the evolved GSM, when location based servers are in place, it will be possible to locate the subscriber within 50-70 m. In case an emergency call is received, the operator will be able to check the location where the subscriber is based and then direct the emergency services to the location faster than it happens currently.
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Figure 44 shows the handling of emergency calls:
Fig. 44 Handling Emergency Calls
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11
Appendix
The End-to-End Service and UMTS BS On its way from the Terminal Equipment (TE) to another, the traffic has to pass different bearer services of the network(s). A TE is connected to the UMTS network by use of a MT. The end-to-end service on the application level uses the bearer services of the underlying network(s). As the end-to-end service is conveyed over several networks (not only UMTS), it is not subject for further elaboration in the present document. The end-to-end-service used by the TE is realized by using a TE or MT local BS, a UMTS BS, and an external bearer service. TE/MT local bearer service is not further elaborated here as this bearer service is outside the scope of the UMTS network. The UMTS operator provides various services or UMTS QoS offered by the UMTS BS. The external bearer service is not further elaborated here as this bearer may be using several network services, such as another UMTS bearer service. The Radio Access Bearer Service and the Core Network BS zezenenu.und.lmm/kucusiqa.en.slo
The UMTS bearer service consists of two parts, the radio access BS and the core network BS. Both services reflect the optimized way to realize the UMTS bearer service over the respective cellular network topology taking into account aspects such as, mobility and mobile subscriber profiles. The radio access BS provides confidential transport of signaling and user data between MT and CN Iu Edge Node with the QoS adequate for the negotiated UMTS BS or with the default QoS for signaling. This service is based on the characteristics of the radio interface and is maintained for a moving MT.
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The Radio BS and the Iu-BS The radio access bearer service is realized by a radio bearer service and an Iu-BS. The role of the radio BS is to cover all the aspects of the radio interface transport. This BS uses the UTRA FDD or TDD. UMTS Terrestrial Radio Access (UTRA) or FDD forms the physical layer in the first phase of UMTS. TDD Time Division Duplex is also expected to be implemented later. To support unequal error protection, UTRAN and MT should have the ability to segment and reassemble the user flows into the different subflows requested by the radio access BS. The segmentation or reassembly is given by the SDU payload format signaled at radio access bearer establishment. The radio BS handles the part of the user flow belonging to one subflow, according to the reliability requirements for the subflow. The Iu-BS together with the physical BS provides the transport between UTRAN and CN. Iu-BS for packet traffic shall provide different BS for variety of QoS. The core network BS uses a generic backbone network service. The backbone network service covers the Layer 1 or Layer 2 functionality and is selected according to the choice of the operator in order to fulfill the QoS requirements of the core network BS. The backbone network service is not specific to UMTS but may reuse an existing standard.
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The Backbone Network Bearer Service
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12
Exercises
Exercise 1 Which UMTS network element contains the security information? USIM RNC AuC SGSN Node B
Exercise 2 Which parameter identifies the subscriber? (Choose three) zezenenu.und.lmm/kucusiqa.en.slo
IMSI IMEI MCC P-TMSI TMSI PIN
Exercise 3 Which location information is known in the UE? (Choose three) LA RA URA 3G-MSC supply area 3G-SGSN supply area
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Exercise 4 Which of the following is/are characteristic(s) of a UMTS bearer? (Choose three) Transparent through the RAN Different lengths of delay Asymmetric connection Variable data rate None of the above.
Exercise 5 Which statement about location update is NOT true?
Location/routing area update takes place when a subscriber moves between LAs and/or RAs. Periodic location updates are not used in UMTS. URA updates are not used in UMTS.
Exercise 6 The URA is used by the core network to keep track of subscribers in the network. True False
Exercise 7 Which statement about the RRC is true? It is only used in GPRS networks. It is a collection of radio access bearers over the air interface. It is a wireless protocol.
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IMSI attach is always made when the terminal is switched on.
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All of the above.
Exercise 8 Which term defines process of requesting a subscriber to contact the network? IMSI attach Location update Paging Bearer allocation
Exercise 9 Which statement best describes authentication? Security of the user information on the air interface zezenenu.und.lmm/kucusiqa.en.slo
IMSI and IMEI checking Supplementary service status checking (by the subscriber) A process used by the GGSN to determine firewall access
Exercise 10 Which equipment performs a cell update and cell reselection when it changes cell within a routing area in Ready mode? UE MSC BSC Node B
Exercise 11 During a PDP context activation process, which information us transmitted from the UE to the SGSN?
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APN PDP GGSN address DNS address TID
Exercise 12 When a subscriber triggers an event in the network, a CDR is generated. What is a CDR? a. Charging data record which is sent to a Billing/Charging Centre b. Caller digital reset to the MSC c. Customer data receipt, which is a bill that is sent to the customer
Charging data record which is sent to a Billing/Charging Centre Caller digital reset to the MSC Customer data receipt, which is a bill that is sent to the customer All of the above.
Exercise 13 SMS messages can be sent via the SGSN. True False
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d. All of the above.
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12.1
Solutions
Exercise 1 (Solution) Which UMTS network element contains the security information? USIM RNC AuC SGSN Node B
Exercise 2 (Solution) zezenenu.und.lmm/kucusiqa.en.slo
Which parameter identifies the subscriber? (Choose three) IMSI IMEI MCC P-TMSI TMSI PIN
Exercise 3 (Solution) Which location information is known in the UE? (Choose three) LA RA URA 3G-MSC supply area 3G-SGSN supply area
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Exercise 4 (Solution) Which of the following is/are characteristic(s) of a UMTS bearer? (Choose three) Transparent through the RAN Different lengths of delay Asymmetric connection Variable data rate None of the above.
Exercise 5 (Solution) Which statement about location update is NOT true?
Location/routing area update takes place when a subscriber moves between LAs and/or RAs. Periodic location updates are not used in UMTS. URA updates are not used in UMTS.
Exercise 6 (Solution) The URA is used by the core network to keep track of subscribers in the network. True False
Exercise 7 (Solution) Which statement about the RRC is true? It is only used in GPRS networks. It is a collection of radio access bearers over the air interface. It is a wireless protocol.
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IMSI attach is always made when the terminal is switched on.
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All of the above.
Exercise 8 (Solution) Which term defines process of requesting a subscriber to contact the network? IMSI attach Location update Paging Bearer allocation
Exercise 9 (Solution) Which statement best describes authentication? Security of the user information on the air interface zezenenu.und.lmm/kucusiqa.en.slo
IMSI and IMEI checking Supplementary service status checking (by the subscriber) A process used by the GGSN to determine firewall access
Exercise 10 (Solution) Which equipment performs a cell update and cell reselection when it changes cell within a routing area in Ready mode? UE MSC BSC Node B
Exercise 11 (Solution) During a PDP context activation process, which information us transmitted from the UE to the SGSN?
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APN PDP GGSN address DNS address TID
Exercise 12 (Solution) When a subscriber triggers an event in the network, a CDR is generated. What is a CDR? a. Charging data record which is sent to a Billing/Charging Centre b. Caller digital reset to the MSC c. Customer data receipt, which is a bill that is sent to the customer
Charging data record which is sent to a Billing/Charging Centre Caller digital reset to the MSC Customer data receipt, which is a bill that is sent to the customer All of the above.
Exercise 13 (Solution) SMS messages can be sent via the SGSN. True False
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d. All of the above.
Signaling Protocols Overview
Signaling Protocols Overview
Contents
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1
Module Objectives.....................................................................................3
2 2.1 2.2
Introduction to UMTS Signaling.............................................................. 4 Understanding the Bearer and the Need for Signalling .............................. 4 UMTS Network Structure............................................................................ 7
3 3.1 3.2 3.3
Transport Plane: Access Stratum........................................................... 9 What is ATM?..............................................................................................9 Common Channel Signaling - 7 (CCS7)...................................................16 Implementation of the Transport Layers ................................................... 20
4 4.1 4.2
Control Plane: Serving Stratum.............................................................25 Iub Interface Control Plane: Node B Application Part.............................. 25 Iur Interface Control Plane: Radio Network Subsystem Application Part......................................................................................... 26 Iu Interface Control Plane: Radio Access Network Application Part......................................................................................... 29
4.3 5
User Plane: Application Stratum........................................................... 35
6
UMTS Release 4 Architecture................................................................ 38
7 7.1
UMTS Release 5 Architecture................................................................ 44 Basic IMS signaling flows ......................................................................... 46
8 8.1 8.2 8.3 8.4 8.5 8.6
Appendix.................................................................................................. 50 Internet Protocol ........................................................................................50 Internet Protocol Version 4 ....................................................................... 53 Internet Protocol Version 6 ....................................................................... 56 IP Routing and Routers.............................................................................58 Port Numbers and Network Address Translation..................................... 61 Components in IP networks...................................................................... 64
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Function of the UMTS Interfaces – A Summary ....................................... 72
9 9.1
Exercises..................................................................................................75 Solutions....................................................................................................80
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1
Module Objectives
The aim of this module is to give the students the conceptual knowledge needed for explaining how basic signaling protocols are implemented in a Universal Mobile Telecommunications System (UMTS) network. Topics to be covered in this module include understanding signaling and visualizing the different layers and protocol stacks. For each layer in the signaling stack the student is expected to give short explanation of its function. After completing this module, the participant should be able to: Explain the concept of signaling and its bearer. Explain in briefly Transport Plane, Control Plane, and User Plane signaling protocol. Explain NBAP, RNSAP, and RANAP. Briefly explain signaling protocols on UMTS Network Release 4 and 5.
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2
Introduction to UMTS Signaling
You can visualise a UMTS network in different ways from different perspectives. One way tovisualize a UMTS network is through the function of the network in terms of how the traffic is handled. Another approach is to study the functions of the network elements. In this module, you will learn about the network from the point of view of the functions and structure of the interfaces.
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Figure 1 shows the Release 99 of the UMTS architecture with the different interfaces:
Fig. 1 Combined GSM/UMTS Network Architecture (Release 99)
2.1
Understanding the Bearer and the Need for Signalling
The user traffic, known as the user plane, is carried through the network from the mobile to the core network on a bearer. In GSM, the traffic channel is the bearer. In UMTS, a bearer is a varied bit rate and is allocated depending on the needs of the subscriber. The actual data in the bearer is transparent to the network.
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As the bearer is passing through the network elements, you need to control its activities. Therefore, one network element must be capable of sending and receiving activity control related messages to other network elements. The messages can contain control-related information, such as the channel allocation, about an activity. This process of sending messages to control the activity of a bearer is called signaling. Signaling is used between the User Equipment (UE) and the core network elements, Serving GPRS Support Node (SGSN) and Mobile Switching Center (MSC) or Visitor Location Register (VLR), to perform mobility and session management functions such as a location or paging. The UE and the MSC/VLR conduct peer-to-peer signaling to manage the UE’s mobility. Other network elements are within the transmission path of the mobility management signaling information, such as the Node B, the Radio Network Controller (RNC), and other switching network elements. In the case of mobility management signaling, all the network elements between the UE and the MSC/VLR transparently transmit the mobility management signaling information as messages; they are not the end-points of these messages. Figure 2 illustrates the creation of bearer through the network elements:
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Fig. 2 Creation of Bearer in Network
The higher-layer signaling messages found in mobility management, such as a location update, are used between the UE and the core network elements MSC/VLR and SGSN. However, the UE is not connected directly to the core network, but through the Radio Access Network (RAN). As a result, the lower-layer signalling to control the connection is needed to ensure that the higher-layer connections are possible. This is the concept of the stack. The mobility management messages can only be transmitted if the connection through the RAN exists. Therefore, another signaling layer is used to control the radio
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connection through the RAN. In addition, an even lower level of signaling is used to control the actual radio link. There are basically two types of information, the user data and the control information. In the case of the Radio Access Bearer (RAB), the data is the user plane. A signaling link is required between network elements including Node B to RNC, RNC to CN, and RNC to RNC, to instruct the RNC, Node B, and/or core network elements MSC and SGSN on how to manage the signaling link.
Fig. 3 Relationship between the RAB and the RRC
As shown in Figure 3, a signaling protocol is used to control the RABs and RRC connection in the Air Interface.
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Figure 3 shows the user plane information between the terminal and the core network elements through the UMTS network by use of the RAB:
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2.2
UMTS Network Structure
Functionally a UMTS network can be presented as an arrangement of layers containing the message flows and procedures performed between separate access points. Each layer in the network is called a Stratum. The complete view of Stratums is presented in the UMTS 3GPP 23.101 specification. In this context, the following three are the most important Stratums are: 1.
2.
3.
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Access Stratum - Contains the message flows and procedures needed to establish the connection between the Mobile Terminal (MT) and network (roughly RNC in this case). Serving Stratum - Handles message flows and procedures where the USIM+MT, which is the same as UE, and the network establish a service. Service in this context means, for instance, setting up a bearer for further purposes. These message flows are transmitted transparently over the Access Stratum. Application Stratum – Handles message flows and procedures related to the user's applications. Therefore, the scope of this layer is wider as compared to Access and Serving Stratum. For example, the UE requests a certain URL over an Internet browser application. The UMTS network only provides the 'pipe' through the Serving Stratum. However, the actual HTML page associated with the requested URL is downloaded from the Internet service provider.
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Figure 4 shows the three important Stratums in the UMTS network:
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Fig. 4 Access, Serving, and Application Stratum
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3
Transport Plane: Access Stratum
Transport plane provides a means to establish the physical connection is between the MT and the network. As the network consists of separate entities limited by the open interfaces, the transport plane is adapted to those interfaces, too. In UMTS transport plane, different physical connections can be used. However, the specifications have based the main connection on Asynchronous Transfer Mode (ATM).
3.1
What is ATM?
The basic idea behind ATM is to split the information flow to be transmitted into small pieces called packets, attach address tags to those packets, and then transfer the packets through the physical transmission path. The receiving end collects the transmitted packets and retrieves the original information flow from the contents of the packets. The packet containing transmitted information is officially called the ATM cell. zezenenu.und.lmm/sumeyeqi.en.slo
Figure 5 shows the structure of an ATM cell:
Fig. 5 ATM Cell
One ATM cell consists of two parts, a 5-byte-long header that contains the address information and payload that contains the transmitted data. The header in an ATM cell is short as compared to other, conventional protocols and messages. As a result, the limitations are set on what can be done using header information. However, at the same time, the effectiveness of data transmission is high. The addressing overhead is 5 / (5+48) 9.5 %. ATM cells are of the following two types: 1.
2.
User-Network Interface (UNI) cell - UNI cell is used for communication between ATM endpoints and ATM switches. For example, between Node B and RNC. Network-Node Interface (NNI) cell - NNI cell is used for communication between ATM switches. For example, between two MGW or two RNCs.
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3.1.1
Virtual Path and Virtual Channel
One ATM transmission path may consist of several Virtual Paths (VP), which further contain Virtual Channels (VC). One ATM transmission path may consist of several VP, which further on contain VC. Figure 6 shows the Transmission path, VP and VC in ATM:
A virtual path is a semi-permanent connection simultaneously handling many VCs. Actual data is transferred in ATM cells over the VCs. From the point of view of UMTS, an ATM transmission path is between the Bearer Services (BSs) and the RNC. In case of a loop transmission, the transmission path contains many VPs, for example one per BS, and the VCs in the VP are set up on per call basis. The bandwidth of the VC varies depending on the BS used. Figure 7 illustrates the concept of VCs and VPs in the transmission of an ATM cell:
Fig. 7 VP and VC in the Transmission of an ATM Cell
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Fig. 6 VP and VC in an ATM Transmission Path
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3.1.2
ATM Header Content
Figure 8 shows how the UNI cell is structured:
Fig. 8 ATM UNI Cell Structure
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One main objective has been to establish a very lightweight transmission system. As a result, the payload of an ATM cell is not protected with checksum method(s). Nowadays this is possible because the networks adapting ATM already have high quality and the terminals used are able to perform error correction themselves, if required. The header of an ATM cell contains address information. The most essential fields in the header are: Virtual Path Identifier (VPI) – Is the identifier for a VP. In general terms, it is an identifier for a constantly allocated semi-permanent connection. Virtual Channel Identifier (VCI) – Is the identifier for a VC. This field is long because there may be thousands of channels to be identified within one VP. For example, multimedia applications may require several VCIs simultaneously; one VC per multimedia component. Payload Type (PT) - Indicates whether the 48-byte payload field carries user data or control data. Cell Loss Priority (CLP) - Is a flag that indicates the priority of the ATM cell. If CLP = 1, the priority of the cell is considered low. The system may lose this less important ATM cell, if required. Header Error Control (HEC) – Is a byte long field that contains data for performing error detection on the ATM cell header. The ATM cell header is error protected instead of the payload because the failure in the ATM cell header is more serious than in payload. For example, due to a header error, the ATM cell may be delivered to the wrong address. The error correction mechanism used is the ATM cell header is able to detect all errors and one failure can be corrected.
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3.1.3
The ATM Layers
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Figure 9 shows ATM can be divided into three main protocol layers:
Fig. 9 Layered Protocol Structure of ATM
The three main layers of the ATM protocol stack are: 1.
2.
3.
The physical layer, which is responsible for defining the physical transmission medium, such as E1 at 2 Mbps or SDH STM-1 at 155 Mbps. Issues like electrical characteristics and coding and decoding are handled by this layer. The ATM layer, which takes care of insertion and extraction of the cell header to and from the 48-octet payload. In addition, multiplexing and switching of the ATM cells is performed in this layer. The ATM Adaptation Layers, (AAL) which are responsible for mapping the data from higher layers to the ATM cells and bringing the data from the ATM cells to the higher layers. There are four different AALs. These will be described later in this document.
Note: Further subdivision and explanations can be made, but it is outside the scope of this chapter to examine these different layers further.
3.1.4
ATM Adaptation Layers
An ATM layer as such is a very simple bit transport media and, in theory, suitable for transmission purposes. In practice, the ATM layer must be adapted to the higher protocol layers and the lower physical layer. ITU-T has defined ATM service classes for ATM adaptation layers. The original idea was that each
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service class from A to D should correspond to one AAL from 1 to 4.
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Figure 10 shows the four AALs:
Fig. 10 ATM adaptation layers
The four service classes of the ATM are: 1.
2. 3. 4.
Constant Bit Rate Service (CBR) - The CBR may be used by any transparent data transfer, and the resources are allocated on the peak data rate basis. Unspecified Bit Rate Service (UBR) - The UBR uses free bandwidth when available. If there are no resources available, queuing may occur. Available Bit Rate Service (ABR) - The ABR is used when the user service has a minimum bit rate defined. Otherwise, the bandwidth is used as in UBR. Variable Bit Rate Service (VBR) - The VBR provides variable bit rate based on statistical traffic management.
Corresponding to the preceding four services, the five AALs are: 1. 2. 3. 4.
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AAL1 offers synchronous mode, connection-oriented connection and constant bit rate for the services requiring this kind of adaptation. AAL2 offers synchronous mode, connection-oriented connection with variable bit rate for the service using this adaptation. AAL3/4 offers asynchronous mode, connectionless connection with variable bit rate. AAL5 offers asynchronous mode, connection-oriented connection with variable bit rate.
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From the point of view of UMTS, AAL2 and AAL5 are interesting alternatives. AAL2 can be used for Iu-Circuit-Switched (CS), Iur, and Iub user plane connections. AAL5 can be used for control information and Iu-Packed-Switched (PS) user plane data transmission. The main difference between AAL2 and AAL5 is that AAL2 requires strict timing between the source and destination. Due to this, AAL2 is especially suitable for real-time services, such as speech or video. AAL5, unlike AALs, enables efficient transmission capability for non-real-time services and applications, towards the PS core network. Generally speaking, AAL is divided into two sub layers: Convergence Sub Layer (CS) - The CS sub layer adapts AAL to the upper protocol layers. Depending on the case, the CS sub layer may be divided further on into smaller entities. Segmentation and Re-Assembly Sub Layer (SAR) - The SAR sub layer splits data to be transmitted into suitable payload pieces. In addition, in the receiving direction it collects payload pieces and merges them back to original data flow. Figure 11 shows the two AAL sub layers: zezenenu.und.lmm/sumeyeqi.en.slo
Fig. 11 General Structure of AAL
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ATM Example
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Figure 12 shows a simplified example of ATM use in the Iub interface:
Fig. 12 Example of ATM Use
Note the relationship between VC, VP, and ATM transmission path.
3.2
Common Channel Signaling - 7 (CCS7)
Note: This section repeats CCS7 information from the GSM courses (GSM SYSTRA, DX, and NSS courses), and may be considered as an optional topic. CCS7 is a widely used signaling method in telecommunications.
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Figure 13 shows the basic CCS7 implements the protocol stack:
Fig. 13 CCS7 Protocol Stack zezenenu.und.lmm/sumeyeqi.en.slo
The CCS7 signaling connections are usually 64 kb/s timeslots of the Pulse Code Modulation (PCM) trunks. However, this is not always the case. Due to the increasing demand, a broadband version of the CCS7 basic protocol stack also exists. The CCS7 basic protocol stack provides signaling connections, their control, and basic signaling routing functionality. If more sophisticated requirements exist, one must add functionality by adding more protocols to the protocol stack. For example, to offer connection-oriented and connectionless services within a CCS7 environment, Signaling Connection Control Part (SCCP) protocol is required. This protocol lies on top of the basic CCS7 protocol stack. The CCS7 uses three types of messages: 1.
2.
3.
Fill-In Signalling Unit (FISU) - FISU only contains sequence and indicator bits for acknowledge purposes; it does not contain any upper-layer information. The signaling channel must be populated all the time. Therefore, if no data needs to be sent, the signalling node sends FISU. Link Status Signalling Unit (LSSU) - LSSU is sent when the CCS7 nodes need to negotiate or change a signaling channel status, or when they have to inform each other about other maintenance activities. Message Signalling Unit (MSU) - MSU is sent when there is some upper layer information to be delivered.
The basic element for CCS7 signaling information transmission is the signaling link. Signaling link is a data link layer connection between two signaling nodes. Both nodes identify a signaling link with a unique number, Signaling Link Code (SLC). The SLC or Signaling Link Set (SLS) should be same in both ends of the
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signaling link. Checking whether the SLCs are the same is one of the functions for which the LSSU messages are used. SLS is group of signaling links wherein one SLS contains a maximum of 16 signaling links. Further a group of SLS can be termed as Route set. Figure 14 shows CCS7 signaling link:
One signaling link between two nodes is able to handle certain amount of signaling traffic. However, eventually more links will be required. The set of signaling links between two signaling nodes is called a signaling link set. Figure 15 shows a signaling link set:
Fig. 15 CCS7 – Signalling Link Set
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Fig. 14 CCS7 – Signaling Link
Signaling Protocols Overview
For proper SLS, every signaling link within a signaling link set must have a unique SLC. The signaling traffic is carried through all the signaling links within the signaling link set. Usually, a signaling session, such as the signaling related to ISUP call set-up, is carried through using the same signaling link for all messages. If load sharing is used, the MTP level is able to distribute messages of one signalling session over several links. In CCS7 it is possible that the actual traffic path is geographically allocated in a different way from the related signaling. That is, two nodes may have direct traffic connections, but the signaling related to those connections may be handled through other nodes. In this case, the signaling node that handles the rerouting of the messages is called Signaling Transfer Point (STP). In the originating signaling node, the routing entity on the MTP level is called signaling route set. Signaling route set is the collection of the signaling routes, through which a certain SPC can be achieved.
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Figure 16 shows a signaling route set:
Signaling route is in practise the same as the signaling link set, but the difference here is that signaling link set is not aware of the STP facility whereas the signaling route is.
3.3
Implementation of the Transport Layers
3.3.1
Air (Uu) Interface
The transport plane of the Uu Interface covers the three lowest layers of the OSI stack. Layer 1, the physical layer, uses Wideband Code Division Multiple Access (WCDMA) – Frequency Division Duplex (FDD)/Time Division Duplex (TDD) technology. The Layer 1 is controlled by Layer 2, the data link layer. The structure of Layer 2 in the Uu Interface is different from other interfaces. Layer 2 has the following two sub layers in the Uu Interface: 1.
2.
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Media Access Control (MAC) - Physically implements radio link management tasks, such as, radio link set-up, maintaining the physical radio channel configuration, error protection, encryption, and radio link deletion. Radio Link Control (RLC) - Mainly performs flow control-related activities such as instance data block sequencing. The functionality of the RLC is similar to Layer 2 of other interfaces.
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Fig. 16 CCS7 – Signaling Route Set
Signaling Protocols Overview
The Layer 3 of the Uu Interface contains functions needed for the transport plane control. The control entity is called Radio Resource Control (RRC). RRC manages the physical layer and its activities whenever required. If, for example, a radio link is to be set up, the RRC gives a command to perform this activity. The command is delivered through the RLC to MAC, and MAC performs the activity. Finally, the radio link set-up is carried through the Layer 1. The idea behind this kind of protocol stack in the Uu Interface is to carry normal Layer 2 functions, and at the same time make the system able to carry the extra control functions required by the Radio Interface (MAC – RLC division).
3.3.2
Iub, Iur, and Iu Interfaces
In the Iub Interface the transport plane consists of ATM and its adaptation layer(s) located on top of the physical layer. The physical layer could be any media providing constant bit rate with adequate bandwidth such as PCM(s), Plesiochronous Digital Hierarchy (PDH), or Synchronous Digital Hierarchy (SDH). Figure 17 shows the transport plane of the Iub Interface:
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Fig. 17 Iub Interface Transport Plane
In the Iur Interface between Serving RNC (SRNC) and Drift RNC (DRNC) the construction of the transport plane is similar to the Iub. Figure 18 shows the transport plane in the Iur Interface:
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Signaling Protocols Overview
In the Iub and Iur Interfaces ATM uses two adaptation layers, AAL2 and AAL5.
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Fig. 18 Iur Interface Transport Plane
Signaling Protocols Overview
Figure 19 illustrates the same solution is implemented in the Iu CS Interface:
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Fig. 19 Iu-CS Interface Transport Plane
In the Iu-PS Interface, only AAL5 is used. In other respects the transport plane is similar as in the Iu-CS, Iur, and Iub Interfaces.
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Figure 20 shows the transport plane in the Iu PS Interface:
To conclude, in UMTS the transport plane provides variable speed packet type of transmission media over constant-bit-rate physical layer. Because the services using the transport plane set different Quality of Service (QoS) requirements, such as real time, non-real time, and delay, for the connection, the transport plane must use different adaptation layers in order to handle the requirements correctly.
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Fig. 20 Iu-PS Interface Transport Plane
Signaling Protocols Overview
4
Control Plane: Serving Stratum
The control plane carries signaling that facilitates the functions of the Service Stratum. These are transparent for the transport plane.
4.1
Iub Interface Control Plane: Node B Application Part
In the Iub Interface the control plane is maintained by the signaling protocol Node B Application Part (NBAP). NBAP is a Layer-3 protocol at the Iub interface. In order to adapt the NBAP properly on top of AAL5, some convergence protocols are required. Figure 21 shows the control plane in the Iub Interface:
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Fig. 21 Iub Interface Control Plane
NBAP procedures are divided into the following two groups: 1. 2.
Common Dedicated
Common NBAP procedures are used to create new UE contexts and to control Broadcast Control Channel (BCCH) broadcast information. The Iub Interface always contains one signaling link for the common NBAP procedures and there may be several signaling links for dedicated NBAP procedures. When a UE establishes connection to the network, the control plane is used. Because the UMTS network uses very sophisticated signaling methods, all seven layers of the OSI model are required for this purpose. After establishing the control plane, the UE may start to use its own applications, which may also require signaling (user plane).
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Signaling Protocols Overview
Control plane means the signaling resources attached for signaling connection set-up issues between two signalling nodes. In case of Iub Interface, the control plane is established between the Base Station (BS) and the RNC. The signaling connection set-up case is radio link set-up.
4.2
Iur Interface Control Plane: Radio Network Subsystem Application Part
Between the RNCs, the control plane is maintained by the signaling protocol Radio Network Subsystem Application Part (RNSAP).
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Figure 22 describes some convergence protocols are required to make RNSAP suitable over the ATM:
Fig. 22 Iur Interface Control Plane
In UMTS-RAN, the RNC nodes may have direct connections among themselves. This connection implements the Iur Interface between the SRNC and the DRNC. The term Serving RNC (SRNC) means, the RNC controlling the connection that is, performing the bearer – radio link mapping. The DRNC means an RNC involving radio link addition, deletion, or reconfiguring procedure without the bearer–radio link mapping control. The Iur Interface procedures are controlled by the RNSAP signalling protocol. The most important Iur Interface procedures are involved in: 1. 2. 3. 4.
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Radio link Radio link Radio link Radio link
set-up addition reconfiguration deletion
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Figures 23 illustrates the radio link set-up:
Fig. 23 RNSAP: Radio Link Set-Up
Figure 24 illustrates the radio link addition: zezenenu.und.lmm/sumeyeqi.en.slo
Fig. 24 RNSAP: Radio Link Addition
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Figure 25 illustrates the radio link reconfiguration:
Fig. 25 RNSAP: Radio Link Reconfiguration
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Figure 26 illustrates the radio Link Deletion:
Fig. 26 RNSAP: Radio Link Deletion
In addition to these procedures that handle the activities related to the DRNC Iub Interface, the Iur Interface and RNSAP handle the situation where the SRNC functionality is transferred from the original SRNC to a DRNC. This type of a case will occur if the first radio link, which is opened when the UE context was created, has to be deleted due to changed radio conditions. An example of such as case where the first radio link has to be deleted is when the UE moves away from the SRNC coverage.
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4.3
Iu Interface Control Plane: Radio Access Network Application Part
In the Iu interface the control plane is maintained by the signaling protocol Radio Access Network Application Part (RANAP). Figure 27 some convergence protocols are required to use RANAP over the ATM:
Fig. 27 Iu Interface Control Plane zezenenu.und.lmm/sumeyeqi.en.slo
In UMTS Release 99, the convergence protocols are expected to be primarily CCS7-based. This is MTP either normal or broadband and Service Connection Control Protocol (SCCP), offering both connection-oriented and connectionless services for the RANAP over the Iu Interface. RANAP is a very important protocol containing numerous procedures. It maintains the Iu Interface control plane and handles activities between the RAN and the core network domains. Due to its location, it is able to handle both circuit-switched and packet-switched traffic-related activities.
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The RANAP performs two kinds of activities: 1. 2.
Connection management between the RNC and the core network domain. The Iu interface carries information related to the UE and the CN domain(s), they exchange signalling information on the control plane. Subscriber authentication could be this kind of procedure where the RNC has no role, but where it carries the related signalling information through itself.
The UMTS network is able to handle all kinds of traffic created by different services the subscribers use. Some of the services used Real Time (RT) services. These services require dedicated connection through the UMTS network. The connection should provide a constant, fixed bit rate for such cases. However, Non-Real Time (NRT) traffic does not require a constant bit rate.
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The dedicated connection established over RAN, between the UE and the core network, is called RAB. The core network domains are the entities setting up, modifying, maintaining, and deleting bearers. In the CN circuit domain, the bearer is established by the Serving MSC/VLR, which negotiates the RAB and its features over the Iu Interface with the SRNC. In the CN packet domain the same task is performed by the SGSN.
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Figure 28 shows the RAB and CN domains:
Fig. 28 RAB and CN Domains
Before the RAB can be allocated, there must be at least one active radio link established between the UE and the SRNC. The RAB can be considered to be a collection of resource point definitions attending to the connection between the UE and the core network. Examples of these types of resource points are AAL2 ID and bearer ID that uniquely defines the RAB in SRNC and Serving MSC/VLR or SGSN. zezenenu.und.lmm/sumeyeqi.en.slo
Bearer allocation always starts from the core network side. The signalling resources required for that purpose are supplied with the signalling protocol RANAP with the Iu interface. Inside the RAN, NBAP is also attending to the procedure In a UMTS network, the term bearer and its management has the same content in both of the core network domains delivering traffic. The procedures related to the RAB assignment are also the same. Consider examples of three procedures in which the RANAP is involved. The first one is the bearer assignment. As it was explained in transaction examples, the core network domain is responsible for bearer assignment. The procedure itself is somewhat simpler than in 2G. Figure 29 describes two messages, RAB Assignment Request and RAB Assignment Complete:
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Signaling Protocols Overview
The RAB Assignment Request may contain information about several bearers and the action to perform on them, such as create, modify, or delete. Therefore, there is no separate procedure for bearer modification or deletion. When the RAB Assignment Request message arrives at the RNC, the RNC actually binds together the bearer and related radio links, thereby enabling the user traffic between the UE and the core network. Figure 30 describes the RAB bearer deletion procedure:
Fig. 30 RANAP bearer deletion
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Fig. 29 RANAP Bearer Assignments
Signaling Protocols Overview
The deletion of the bearer may be initiated either by the RAN or by the core network. If the deletion is initiated by the RAN, the RAB Release Request message is used. If the deletion is initiated by the core network domain, the RAB Assignment Request message is used. From the RNC point of view, the RAB deletion means that the binding between the RAB and the radio links is released and the NBAP/RNSAP/RRC procedures for radio links release can be started. However, this can only be done provided that the UE does not have any traffic ongoing through other bearers. Figure 31 describes the RANAP Serving RNC relocation:
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Fig. 31 RANAP Serving RNC relocation
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Signaling Protocols Overview
When the UE moves in the RAN, there will be a situation where the UE context originally created is not controlled with a reasonable SRNC. Therefore, the SRNC functionality must be carried from one RNC to another. This procedure is called Serving RNC relocation and it requires activities to be performed in two interfaces, Iu and Iur. When the very first radio link created for the UE context is about to be released and the original Serving RNC identifies a need for SRNC relocation, it informs the desired new SRNC through the core network domain(s) about the need for the relocation. The new possible RNC acknowledges this request through the core network, and the core network starts preparations for bearer switching by assigning bearers towards the new Serving RNC.
When the new Serving RNC realises that the new bearers are working properly, it sends the message Relocation Complete thereby informing that the rest of the connections through the Iu Interface towards the original Serving RNC can be released.
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When the Relocation Command reaches the original Serving RNC, it indicates that the core network is aware of the issue and the bearers towards the new Serving RNC have been allocated. At this stage, the original Serving RNC starts the relocation in the Iur Interface by sending the Relocation Commit. After the new Serving RNC identifies that the relocation has started, the information about the readiness comes to the original Serving RNC through the core network in the message Relocation Detect. This is also an indication to start the bearer switching, such that new bearers towards the new Serving RNC are used, and the old bearers towards the original Serving RNC are released.
Signaling Protocols Overview
5
User Plane: Application Stratum
The user plane signaling takes place between the application(s) of the UE or user and the destination over the physical connection established on the transport plane. The signaling is performed using the facilities offered by the control plane. In the Uu interface, the user plane consists of the Dedicated Physical Data Channel (DPDCH) allocated for the connection and the data carried by the DPDCH. Forward Access Channel (FACH) carries the information coming from the Logical CCCH, CTCH and DCCH, that is, from common and dedicated control channels. Dedicated Channel (DCH) channel carries the combination of the user traffic(s) and control information. Random Access Channel (RACH), the transport channel carries initial access information when required.
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DCH is the only dedicated transport channel; the other channels are common ones. The DCH carries information coming from the Logical DTCHs and DCCH. It should be noted that one DCH may carry several DTCHs, depending on the case. For example, a user may have a simultaneous voice call and video call active. The voice call uses one Logical DTCH, and the video call requires another Logical DTCH. Both of these, however, use the same DCH. Figure 32 illustrates the Iub interface in User Plane:
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Fig. 32 Iub User Plane
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Figure 33 illustrates the Iur interface in User Plane:
Fig. 33 Iur Interface User Plane zezenenu.und.lmm/sumeyeqi.en.slo
Figure 34 illustrates the Iu interface user planes for CN circuit and packet domain:
Fig. 34 Iu interface user planes for CN circuit and packet domain
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Signaling Protocols Overview
6
UMTS Release 4 Architecture
UMTS networks are designed to offer a wide range of multimedia services. For a wide range of services to be offered, the core network must offer more efficient and flexible transport options compared to the Rel.99 network. Therefore, a wide range of bearers must be made available in the core and radio access network for the subscriber. Currently, the exchanges and MSCs are optimized for voice transport. An MSC is responsible for the following tasks: Call control Service provisioning Bearer control and bearer management
Beginning with UMTS Release 4, call control and bearer control and management are separated. The planes are separated in the UMTS Release 4 circuit switched domain. The UMTS Release 99 network elements MSC, VLR, and Gateway Mobile Switching Centre (GMSC) are substituted by certain network entities. The network entities are MSC-Server, GMSC-Server, and Circuit Switched – Media Gateway Function (CS-MGW). Figure 35 shows the release 4 architecture:
Fig. 35 Release 4 Architecture
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With the different tasks combined in one network element, any modification will be expensive and time consuming. Therefore, with a traditional MSC more flexible solutions are requires because it is difficult for operators to react quickly to changing demand in the market.
Signaling Protocols Overview
MSC-Server The MSC-Server is responsible for all the call control tasks of the MSC and VLR. The tasks are as follows: CDR collection. Call control in CS domain performs Call control of mobile originated and mobile terminated calls in the CS domain. VLR functionality temporarily hold the subscriber profile, location information, and identities for all subscribers in the MSC-Server supply area. Interaction with the CS-MGW determines the QoS parameters required for the subscriber’s application. It is then the responsibility of the CS-MGW to make the bearer available. The interaction between MSC-Server and CS-MGW is done via an open interface, based on the ITU-T H.248 standard. Termination of UE-network and network-network signaling: It performs the UE-network signaling through the Iu-CS interface. It performs the network-network signaling, by using signaling protocols such as, the Bearer Independent Call Control (BICC). GMSC-Server zezenenu.und.lmm/sumeyeqi.en.slo
The GMSC-Server adopts the call control tasks of the GMSC. The tasks are as follows: CDR collection Interrogation of the HLR Interaction with the CS-MGW Termination of network-network signaling CS-MGW The CS-MGW is responsible for bearer control. Its functions include: Bearer Control -The requirements for the bearer control are set in the (G)-MSC-Server. The CS-MGW gets this information through an open interface. The CS-MGW needs to determine, whether it can make bearers available in accordance to the QoS parameters set. Bearer Channel Termination - Different transmission technologies may be in use, for example, ATM and IP over Ethernet. Accordingly, the ATM bearer ends in the MGW and the IP bearer begins at the MGW for user data transport. Media Conversion and Payload Processing - If the CS-MGW is interfacing UTMS Terrestrial Radio Access Network (UTRAN), voice information must be processed. for example, voice may be transmitted with 64 kbps in the core network, but for the radio interface, a speed of 12.2 kbps. The UMTS specific voice codec is found in the MGW. The same is true for conference bridges, and echo cancellers. Mobile Specific Functions - A CS-MGW must support mobility specific functions, such as SRNC re-location and handover procedures.
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Figure 36 shows the tasks performed by MSC-Server, GMSC-Server, and CS-MGW:
Fig. 36 Tasks Performed by MSC-Server, GMSC-Server, and CS-MGW
Different Interfaces are explained as below: Nc : The Nc interface is located between two MSC servers. It transports the bearer independent call control protocol used to set up bearer segments between the two servers. The main protocol used here will be BICC. Mc : The Mc interface is between MSC server and MGW. It is used by the MSC server to request the set up, release and modification of transport bearer services. The MGW can issue event notifications towards MSC server on this interface. Nb : The Nb interface works between two MGWs.This interface is completely within the transport network plane and first of all carries the user data traffic. Therefore the Nb interface provides transport bearer services. The control of these transport bearer services is also done via Nb using a Bearer Control Protocol (BC) specific to the transport technology used. The Nb interface between two MGW of course has to transport user data. Hence there is a user plane. For ATM based CN this user plane consists of AAL2 virtual channel connections.
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Like on Iu-CS also here we need a special user plane protocols Nb User Plane (Nb UP) protocols. Nb UP allows like Iu UP to transport structured data through the network, this essential for Transcoder Free Operation (TFO). Because when using TFO for a mobile to mobile call the codec frame structure must be transported end-to-end unmodified. To configure the user data bearer service (AAL2 virtual channel connection), the AAL2 signalling protocol is required between the MGW. On Iu-CS this is called ALCAP, here on Nb these bearer configuration protocols are called BC protocol. In UMTS Release 4, we have signaling between MSC Server and MSC Server (Nc), between MSC Server and MGW (Mc), between MGW and MGW (Nb). In principle the basic method to implement these three interfaces is Direct Connection of Nc. In this case two MSC Servers will have a direct connection with each other. This direct connection implements the Nc interface which carries the bearer independent call control signaling. Mc and Nb interface are implemented as direct connections too. Especially when MGW and MSC Server are built in the same device or are extremely close to each other, the second solution is typically more cost efficient. Figure 37 shows Direct Connection of Nc: zezenenu.und.lmm/sumeyeqi.en.slo
Fig. 37 Direct Connection of Nc
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The Nc interface has to carry the signaling for logical call handling. This means it must be bearer independent. Classically ISUP is used for logical call handling, but ISUP is bearer PCM dependent. Hence, ITU-T has defined a modification of ISUP which is called BICC. In fact, BICC is a bearer independent version of ISUP. BICC works over SIGTRAN message transport. When the MSC Server is doing a logical call control procedure, then the result may be the decision to set up, release or modify transport bearer resources. But the MSC Server no longer is in control of that, but the MGW is. Hence on the Mc interface the MSC Server will instruct the MGW to prepare, establish, release or modify bearer services. The Call Bearer Control (CBC) protocol is used for this purpose. CBC is based on the general framework provided by H.248 including UMTS specific procedures and parameters. CBC can use SS7 over IP, SS7 over ATM for message transport. Here the protocol has the following main tasks: Retrieval of statistics about the bearer connection. Indication of events concerning the bearer connections. Control bearer connection setup, modification and release. Call bearer control CBC protocols are usually specific to the transport technology used, but are also dependent on the system. Therefore, a lot of different CBC are needed in telecommunication. Therefore, ITU-T defined a basic framework for CBC protocols based on the standard H.248. The same framework is also provided by IETF for IP environments, here H.248 is called Media Gateway Control (MEGACO) protocol. H.248 provides a generalized model how to perform bearer connection control between network control plane and transport network plane. CBC require four following elements: 1.
Framework: A framework specifies the functional architecture, interfaces and abstract models.
2.
Messages: Messages are the basic communication units exchanged between functional units defined in the framework.
3.
Procedures: Procedures define rules and actions associated with messages, parameters, signals and events. Parameters, Events, and Signals : Events describe what is detectable and reportable. Signals are various indications running on the bearer (e.g. busy tone). Parameters describe how bearers and related things can be described.
4.
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Trigger and detection of tones and signals on the bearer.
Signaling Protocols Overview
With H.248 especially the framework and the set of messages is defined. Also a basic set of parameters, events and signals comes within H.248. But because different technologies and systems require different parameters, events, signals and procedures it is possible to define so called H.248 packages, which are specific. A CBC now consists of H.248 and a set of mandatory and optional packages. Benefits of Release 4 Release 4 includes the separation of user plane from control plane. This makes it easier to provide efficient bearer services with variable characteristics. The purpose is to offer a better transport resource efficiency and a convergence with the Packet-Switched (PS) domain transport. Another benefit is that the architecture enables the use of a single set of layer 3 signaling protocols on top of different transport resources, such as ATM or IP, Synchronous Transfer/Transport Mode (STM). This feature aims to simplify the protocol stacks involved in mobile communication. The Release 4 architecture allows for a centralization of call control functions to lesser number of MSC servers comparatively. The actual user plane can be switched close to the end user, for example, physical network topology can reflect usage patterns better than before. zezenenu.und.lmm/sumeyeqi.en.slo
The network architecture provides opportunities to utilize statistic multiplexing gain for all services including real-time services, therefore, reducing transmission costs. Calls can be switched at MGW sites without being routed to the MSC server site increasing transmission efficiency further. Due to the higher switching efficiency of Release 4 compared to Release 99 new services can be provided at a low cost to the end users, for example, streaming services. The concept of GERAN is established with Enhanced Data Rates for GSM Evolution (EDGE) / General Packet Radio Service (GPRS). The GERAN standard supports all classical GSM CS voice services such as Full-Rate, (FR), Half-Rate (HR), Enhanced Full-Rate (EFR), and Adaptive Multi-Rate (AMR). Release 4 is a step further to the way to future UMTS architectures, in which advanced multimedia services will be offered. These advanced services require an efficient underlying control and user plane architecture.
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7
UMTS Release 5 Architecture
The UMTS Release offers a wide range of improvements compared to earlier releases. Two of the main new features are the IP Multimedia Subsystem (IMS) and the radio network improvement High Speed Downlink Packet Access (HSDPA). The objective of the IMS is to support applications involving multiple media components per session in a way that the network is able to dissociate different flows with potentially different QoS characteristics associated to the multimedia session.
The fixed Internet multimedia call control Session Initiated Protocol (SIP) defined by the Internet Engineering Task Force (IETF) is chosen as the IMS main protocol for its flexible syntax. SIP also allows for development of common applications and interconnectivity between 3G UMTS networks and fixed IP networks, such as Internet. To transport IMS signaling and user data, IMS entities use the bearer services provided by the PS domain and the UTRAN. With some exceptions, the PS domain and the UTRAN domain consider IMS signaling and IMS applications flows as user data flows. As a result, the impact on existing architecture on non-IMS entities is minimized. As part of the bearer services offered by the PS domain to the IMS, the PS domain supports the handover functionality for maintaining the service while the terminal changes the location. IMS can be used on bearer networks other than PS domain, but this is not defined in Release 5.
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These applications are called IP Multimedia applications. Examples of such applications are multimedia session offering the possibility to add and drop component(s), such as video, audio, end users, or tools as shared online whiteboards. The impact on the network is the creation of a set of new entities, the IMS, dedicated to the handling of the signaling and user traffic flows related to these applications. All IMS entities are located in the Core Network. The impact on non-IMS specific network entities is kept as low as possible.
Signaling Protocols Overview
Figure 38 shows the example of IP Multimedia Subsystem:
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Fig. 38 Example of IP Multimedia Subsystem
The main entities of IMS are as follows: Proxy-Call State Control Function (P-CSCF): This is the first contact point of IMS. It is located in the same network as the Gateway GPRS Support Node (GGSN). The network can be a visited network or the home network. Figure 49 shows the P-CSCF in the visited network. The main task of P-CSCF is to select the Interrogating-CSCF of the Home Network of the user. It also performs some local analysis, for example, number translation, QoS policing. Interrogating-CSCF (I-CSCF): This is the main entry point of the home network: it selects with the help of Home Subscriber Server (HSS) the appropriate Serving-CSCF (S-CSCF). Serving-CSCF (S-CSCF): performs the actual Session Control. This function handles the SIP requests, performs the appropriate actions, for example, requests the home and visited networks to establish the bearers. It also forwards the requests to the S-CSCF/external IP network of other end user as applicable. The S-CSCF might be specialized for the provisioning of a set of service or even a single service.
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The functions described are not network elements. These functions are logical entities of the IMS and the actual implementation may combine the functions in different hardware. The IMS provides the benefits of as follows: IP transport in UTRAN. End to end IP services. IP transport in the core network. Simpler service integration due to simplified protocol stacks. Easy integration and enabling of instant messaging, information, and real-time conversation services.
7.1
Basic IMS signaling flows
When a user has activated the signaling PDP context for SIP signaling towards IMS, it must select a Proxy CSCF. This Proxy CSCF will act a local IMS controller to locate the GGSN and related PDP context of a subscriber for mobile terminating services, to decide a about local quality of service policies for PDP context bandwidth allocation, act as proxy or redirect SIP server for SIP signaling from and to UE. To select this P-CSCF a lookup must be performed. This can be done using DHCP (Dynamic Host Configuration Protocol) or without DHCP. P-CSCF Lookup Using DHCP If Packet Data Protocol (PDP) configuration is done with DHCP also the P-CSCF lookup can be associated with it. The following would happen: Signaling PDP Context Activation First of all the UE must trigger a signaling PDP context towards IMS. The standard APN for this purpose is 'IMS' indicating that the IMS network is the destination. Additionally a flag in the Traffic Flow Template (TFT) description is set, which indicates that this PDP context may be used for SIP signaling purposes. Because DHCP is used, the GGSN will allocate an IP address (PDP Address) for the UE, so the invalid address 0 is sent instead.
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P-CSCF Lookup
Signaling Protocols Overview
DHCP Configuration Now the UE has to get the protocol configuration options for the IP stack using the established PDP context. Therefore it sends a DCHP multicast message Discover to the IMS network. The GGSN will intercept this message and route it to a (pre-configured) DHCP server. This one will now make an offer to the UE for IP configuration. This especially includes an IP address and for IMS this will also mean that the domain name of a P-CSCF is given. This offer is returned by the DHCP server to the GGSN which relays it to the correct PDP context of the UE. It can either accept or deny the offer. If it is accepted the UE must request the offer with the DHCP message Request. If the offer is still valid, the DHCP server grants it to the UE with Acknowledgement message. Now the UE IP protocol stack is configured. PDP Address Validation To make the received PDP address valid the GGSN triggers a PDP context modification towards SGSN and UE with the updated PDP address inside. P-CSCF Name-to-Address Resolution
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After PDP address validation, the UE has only the P-CSCF name. It still needs to get the corresponding IP address for it (if not already received instead of the name). This is done using a Domain Name Service (DNS). In general the resolution of the P-CSCF name is done in three steps: 1. 2. 3.
Transport layer determination (NAPTR query). Server name lookup (SRV query). Address lookup (A/AAA query).
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Figure 39 shows the P-CSCF lookup using DHCP:
Fig. 39 P-CSCF lookup using DHCP
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P-CSCF Lookup Without DHCP The P-CSCF lookup can also be done without DHCP. Then the GGSN is responsible to deliver a P-CSCF address. Note that in such a case rather the IP address of the P-CSCF than a name is returned. The P-CSCF address is derived by the GGSN at the time the IMS signaling PDP context is established by the UE. The GGSN may take the P-CSCF address from an internal data base or may request other IMS entities to deliver a P-CSCF address. The exact mechanism is out of scope of the protocol. Figure 40 explains P-CSCF lookup without DHCP:
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Fig. 40 P-CSCF lookup without DHCP
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8
Appendix
8.1
Internet Protocol
Data communications involve the transmission and reception of data between entities across different networks. An entity has the capacity to transmit and receive data. For an entity to function correctly, all entities must agree upon a protocol for successful communication. A protocol is a set of rules defining data communications between entities.
Figure 41 shows the examples of OSI and Transmission Control Protocol/Internet Protocol (TCP/IP) models:
Fig. 41 OSI-Model vs. TCP/IP
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A protocol can define many aspects of communications including what is the nature of communications, how will the entities communicate, and when will the communications take place. Most protocols can be represented in a layered architecture or layered model. Each layer performs a distinct function. Each layer receives a Protocol Data Unit (PDU) from the layer above to it, performs some processing on PDU. Then each layer adds a header to the PDU and sends the resulting PDU to the layer below it. The process of adding headers to the PDU is called encapsulation. If the PDU is larger than an acceptable maximum size due to technological limitations, the PDU may be broken into smaller PDUs. This process is referred to as fragmentation.
Signaling Protocols Overview
The International Organization for Standardization (OSI) model contains following seven layers: 1. 2. 3. 4. 5. 6. 7.
Application Presentation Session Transport Network or Inter-network Data link Physical layers.
Each layer performs a distinct function. The TCP/IP protocol family was originally developed for US military data networks in the late 1970s. The first network to use this protocol was called ARPANET. Since then, the TCP/IP family of networking protocols has grown to its current position as the most widely used data communications protocol both in interconnecting Wide Area Networks (WAN) and in office or corporate Local Area Networks (LAN). Due to the widespread use and relatively easy implementation, the usage of TCP/IP protocols is supported by every WAN and LAN technology that exists.
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Currently, TCP/IP protocols are developed and standardized by the Internet IETF. The website for IETF is www.ietf.org. IETF membership is free and there is no subscription fee for the documents either. Although TCP/IP can be mapped and explained with the classical layered OSI-protocol model, there are some differences. For example, there are no session or presentation layers defined, but the functionality of the session or presentation layers is built directly into application layer protocols. IP is a layer-3 protocol that is used to carry data over different types of network. Internet Protocol (IP) works in connectionless packet mode. In other words, data is transported to the destination without the establishment of a connection between the source and the destination similar to a postal system. Each packet will have an address for both sender and receiver, which is referred to as an IP address. There are two types of IP addresses, private IP addresses and public IP addresses. Public IP addresses are globally unique, in which all IP packets in a public network will have unique IP sender and receiver addresses.
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Figure 42 shows how IP addressing can be compared to street addressing:
Fig. 42 IP Addressing Compared to Street Addressing
IP is used as the interconnection protocol in the Internet. The use of unique addresses means that every machine connected to the Internet can send packets to any other machine connected to the Internet, assuming that this has not been denied for security reasons. Each packet will have an address for the sender and the receiver. Large deliveries may be divided or fragmented into several smaller packets to help transportation. The network does not guarantee when and how the packets will arrive. It is referred to as a best effort network.
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Figure 43 shows four different IP networks interconnected together. If Router 1 has packets that need to go to the Internet, it can send packets via Router 3 in IP Network A or through Router 4 in IP Network B.
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Fig. 43 Example of an IP Network
8.2
Internet Protocol Version 4
An IP address identifies a host on a network. The current version of IP is IP version 4 (IPv4). The length of the IPv4 address is 32 bits. Due to the fact that humans find it difficult to write 32 binary bits, IP address are written in a dotted decimal notation as A.B.C.D. Each number in this notation corresponds to an octet or 8 bits. Each octet has the decimal range of 0 (00000000) to 255 (11111111). For example, the IP address for NSN’s global web site, http://www.nsn.com, is 193.65.100.105. In this address, 193 represents the most significant octet of the IP address. As the range of each octet has been specified, the next issue is the availability of addresses. At the beginning of this section it was mentioned that an IP address consists of 32 bits, and each bit has a binary representation of 0 or 1. Therefore, 232 results in 4295 million addresses approximately. However, not all IP addresses are available because some are reserved for special purposes. For example, the IP addresses 0.0.0.0 and 255.255.255.255 are used for special purposes. The IP address 255.255.255.255 is used for local broadcasting to all hosts across a network.
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An IP address is composed of two parts, the Network ID (Net ID) and the Host ID. The Net ID represents the network to which the host or gateway belongs and the Host ID identifies the specific host within that particular network. The Net ID always precedes the Host ID. The number of bits used to represent the Net ID and the Host ID varies on whether a class or a classless IP addressing is used. All routing functions are based on the Net ID portion of the IP address.
8.2.1
Class Based IP Addressing
The Class based IP addressing was the original mode of allocating addresses. A detailed description of Class based IP addressing can be found in RFC 791. The five classes of IP addressing as follows were defined:
2. 3. 4. 5.
Class A - These addresses were designed for big organizations, which have large number of computers in their network. Class B - These addresses were designed for mid-size organizations, which have large number of computers in their network. Class C – These addresses were designed for small size organizations, which have small number of computers in their network. Class D – These addresses were designed for multicasting purposes. Class E – These addresses are reserved by the Internet for special use. Similarly, class E type addresses have no Net ID or Host ID.
Figure 44 summarizes the characteristics of different classes of IP addresses:
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1.
Signaling Protocols Overview
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Fig. 44 Characteristics of Class Based IP Addresses
In addition, these bits can be used to compute the number of networks supported by each class as well as the number of hosts per network supported by each class. The number of bits can be specified for Net ID and Host ID depending on the class.
8.2.2
Classless Based IP Addressing
The second type of addressing is known as classless addressing. Classless addressing was developed as one of many solutions to address the shortage of IP addresses in the earlier class based addressing. In this scheme, the Net ID is not confined to 7, 14, or 21 bits. The Net ID can be between 2 and 31 bits, therefore, the boundary between the Net ID and Host ID needs to be indicated. A classless IP address is represented as a.b.c.d / x. The ‘/x’ says that first x bits of the IP address is a Net ID. In this addressing scheme, a netmask is used to distinguish between the Net ID and Host ID bits of the IP address. A netmask contains a series of 1s corresponding to the Net ID followed by a series of 0s corresponding to the host ID. The examples of netmask are as follows: Example 1: If IP address = a.b.c.d/24 Then netmask = 11111111.11111111.11111111.0000000 = 255.255.255.0
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Example 2: If IP address = a.b.c.d/23 Then netmask = 11111111.11111111.11111110.0000000 = 255.255.254.0 Example 3: If IP address = a.b.c.d/22 Then netmask = 11111111.11111111.11111100.0000000 = 255.255.252.0
Fig. 45 Bit-wise Anding of IP Address and Netmask
The IP address and netmask are ANDed together bit-wise resulting in the binary representation of the network address
8.2.3
Static and Dynamic IP Addressing
A static IP address is similar to the passport number, which does not change. For example, a computer can be a host in a network that has unique and permanent IP addresses. Every time the user logs into the network the computer will use the same IP address. With a dynamic IP address every time the user log into the network, the network will assign a different address. This address is assigned on demand and can be used by different hosts at different times, but not simultaneously because IP addresses are unique. There is a lease time associated with a dynamically assigned address.
8.3
Internet Protocol Version 6
IPv6 is the latest version of the Internet Protocol developed by IETF. One of the main reasons for the introduction of IPv6 is that the number of IP addresses available with the current IPv4 is running short. The address size of IPv6 is 128
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Figure 45 shows the Bit-wise Anding of IP address and netmask:
Signaling Protocols Overview
bits, which is estimated to last a much longer than the 32 bits in IPv4. There are also other reasons for introducing IPv6 as highlighted in RFC1883: Expanded Addressing Capabilities The increased address space of 128 bits will allow IPv6 to support more levels of addressing hierarchy, more addressable nodes, and simple auto-configuration of addresses. IPv6 also includes a new type of address, anycast address, which is used to send a packet to any one group of nodes in a network. Header Format Simplification In contrast to the header format of IPv4, some of the header fields of IPv6 have been discarded or made optional. This change was invoked to reduce the common-case processing cost of packet handling and to limit the bandwidth cost of IPv6 header. Improved Support for Extensions and Options The changes implemented in IPv6 for header options permit increased efficiency in forwarding. In addition, less stringent limits on the length of options increases the chances of implementing more options in future. Flow Labelling Capability zezenenu.und.lmm/sumeyeqi.en.slo
This is a new capability feature. This feature allows the labelling of packets that belong to a particular traffic flow, for which the user had requested special handling. This includes non-default quality of service or real time service.
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Authentication and Privacy Capabilities IPv4 did not have any authentication and privacy capabilities. This was compensated by the development of IPsec. IPv6 contains many features of IPsec and other features to support authentication, data integrity, and data confidentiality.
8.4
IP Routing and Routers
Router is an IP device that can forward IP packets, which have a destination address other than its own, to other IP devices. The process of selecting the best data link and next hop on the route for the intended destination network is called routing.
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Figure 46 shows a router and the tasks performed by a router:
Fig. 46 A Router and Its Tasks
Routing can be either static or dynamic. In static routing, the router will have a fixed routing table, which includes the destination IP networks and corresponding next hops. In dynamic routing, the routers exchange information on the destination IP networks and corresponding next hops. This dynamic information is exchanged through routing protocols, such as Open Shortest Path First (OSPF), the Routing Information Protocol (RIP), the Interior Gateway Routing Protocol (IGRP), and the Border Gateway Protocol (BGP).
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It is impossible and not practical to know the route to every IP-network in the world, therefore, the routers and the hosts use a default gateway or default route. If accurate information about the destination IP-network is not known, then the packets are sent to the default gateway or default route. The default gateway or default route is typically marked with the address 0.0.0.0 or mask 0.0.0.0 -notation. Figure 47 shows a typical routing table for Router 1:
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Fig. 47 IP Routers and Routing Table
If Router 3 fails, Router 1 will have to find an alternative path to route its packets to the Internet. The alternative path can be used if, Router 1 corrects its routing table by incorporating a new route to the Internet through Router 4.
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Fig. 48 IP Routers and Routing Table
IP is a connectionless protocol and routing will be done individually for each and every packet even if they belong to the same data transfer. Every router between the sender and the receiver performs the routing function. Routers are needed in IP based LAN/WAN networks to interconnect IP network that employ similar or dissimilar lower layer or data link protocols. An IP packet arriving from a network using one type of data link can be easily forwarded to the next hop network, based on another type of data link. If both the sender and the receiver are connected to the same physical data link network or an Ethernet segment and are using IP addresses from different IP sub networks, the packets from one sub network to the other will have to be sent to a router, which has an interface to both sub networks. The router then forwards packets between the two IP sub networks.
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Figure 48 shows IP routers and routing table in case of malfunction:
Signaling Protocols Overview
8.5
Port Numbers and Network Address Translation
Once a packet is delivered to an IP device, the question arises to which application process the transport layer should deliver it. TCP and UDP provide an addressing method to separate different application processes inside the IP-capable devices, and this is referred to as port numbers. Each application will have one or several port numbers to identify the sender and receiver applications. Port numbers can be static or dynamic. On the server side port numbers are typically fixed, and on the client side they are allocated dynamically. Port numbers run from 0 to 65536. Figure 49 shows several applications running simultaneously on one host:
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Fig. 49 Several Applications Running Simultaneously on One Host
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Figure 50 shows that any data transmission between two IP devices is uniquely identified by the IP-address and port numbers using WWW traffic as an example:
Fig. 50 HTTP Request From a Web Browser
8.5.1
Sockets
A socket is simply a combination of the IP address and the port number. Using the port number for identification purposes would be difficult because the same port number can be used on a number of different clients. Sockets allow a server to uniquely identify the process running on a particular client.
8.5.2
Network Address Translation
For security reasons and to save addressing space, some networks have a different addressing space than the Internet. The hosts in these networks use private unregistered IP addresses inside the network. To connect to the Internet, a registered public address is required. Therefore, there has to be some device that performs the translation of a private unregistered address to a public registered address. This task is called Network Address Translation (NAT) and is performed in routers connected to external networks or firewalls.
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Figure 51 shows the NAT:
Fig. 51 Network Address Translation
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In order to save addressing space, network address and port translation can be used. For example, the GPRS backbone network is separated from the external networks. It has a separate address space from the public Internet and GPRS users. The IP addresses given to the users may be public addresses or private addresses from a private network address space other than the ones used for the GPRS backbone. If the users are allocated private or unregistered addresses, they have to be mapped or translated into one or more registered public IP addresses and port pairs. This process is called NAT. If more that one private address is mapped into one public address and different port numbers, the process is called Network Address and Port Translation (NAPT).
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Figure 52 shows the network address and port translation in a GPRS network:
There are two main reasons for using NAT as follows: 1. 2.
Security. The limited number of public IP address available to an operator.
Usage of NAT increases the security of the users, as the internal addresses are not visible to computers outside of the NAT device. From the mobile station's point of view, the NAT function and the GPRS core are transparent.
8.6
Components in IP networks
8.6.1
Domain Name System
The Domain Name System (DNS) is an application layer protocol, which is used to convert difficult-to-remember 32-bit IP addresses to more easily remembered symbolic names, and vice versa. An example of a DNS is gprs.ntc.nsn.com which maps to the IP address 192.168.0.1. The conversion from the symbolic name to the IP address is done in DNS servers. A DNS server is a database containing IP addresses and corresponding symbolic names. A single DNS cannot store the information on all address-name pair.
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Fig. 52 Network Address and Port Translation in a GPRS Network
Signaling Protocols Overview
Figure 53 shows the DNS is based on a hierarchical and distributed model:
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Fig. 53 DNS in Operation
As shown in Figure 50 , the host has to translate the IP address for gprs.ntc.nsn.com. For this, the following steps are performed: 1. 2.
3.
4. 5.
6.
The host sends a DNS query to its local DNS server , asking for the IP address of gprs.ntc.nsn.com. The local DNS server does not know the answer, because it only has a database of the local users. It forwards the query to a predefined root level DNS server . The root level DNS server replies with a list of IP addresses to .com -level DNS servers. The local DNS server sends the query to the .com DNS servers. The .com DNS server replies with a list of IP addresses of the nsn.com -level DNS servers. The local DNS server sends the query to one of the nsn.com DNS servers, which replies with a list of the addresses of ntc.nsn.com -level DNS servers. The local DNS server then forwards the query to one of the ntc.nsn.com DNS servers. The ntc.nsn.com - level DNS server replies with an IP address corresponding to the gprs.ntc.nsn.com DNS name. The local DNS server forwards the reply to the original host.
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To avoid repeating the preceding procedure for every request, all DNS servers and hosts will cache their replies for a short time. So, if the same host sends another request for the same symbolic name, the host would know the right IP address from its cached data without performing all the steps in the preceding procedure. If some other host using the same local DNS server needs the IP address of the same symbolic name, it can retrieve the IP address faster from the local DNS server’s cache.
8.6.2
Dynamic Host Configuration Protocol
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The Dynamic Host Configuration Protocol (DHCP) is used to provide automatic network configuration information from the DHCP server to the DHCP client. From the IP point of view, the important configuration parameters that a client needs to know are the IP address, netmask, and the default gateway. This means that IP addresses are not assigned permanently to any client, but instead they are allocated from a pool of addresses assigned to a DHCP server. In order to avoid ‘ghost’ users using IP addresses they no longer need, the given IP addresses and the other parameters are associated with a lease time. This lease time can be configured to be from few to several days. Before the lease expires, the client has to try to renew the lease. The client must stop using the IP address if the lease expires.
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Figure 54 shows the Distribution of IP addresses from a DHCP server to DHCP clients:
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Fig. 54 DHCP in Operation
A DHCP server can be a dedicated server only or it can be just a part of some other type of server. A DHCP client can be run directly on a host machine as normally is done in an office LAN environment. The DHCP client could be run on a Remote Access Server (RAS), and with some other technique, such as. PPP, the information could be forwarded to the right remote host. Note: Point to Point Protocol (PPP) is a data link protocol used commonly with dynamic serial links such as dial-up modems. In addition to normal datalink functionality, it is also capable of negotiating network layer parameters.
8.6.3
Remote Authentication Dial In User Service
Remote Authentication Dial In User Service (RADIUS) is a protocol used for the centralised control of remote users between several RAS. Each RAS is connected as a client to a central RADIUS server. The RADIUS server has a database that contains the information needed for authentication of the remote users. In addition, dynamic IP addresses can be assigned to remote users using RADIUS.
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8.6.4
Virtual Private Network
A Virtual Private Network (VPN) is a method of securely communicating between a VPN client, such as a user, and the user’s organisation’s network over a public non-secure network such as the Internet. The VPN concept has been around for some time. The concept of VPN was initially used in telephone networks. Only recently have they become popular due to the prevalence of the Internet and advances in security technologies. Nowadays many companies use Internet-based VPNs because it is more cost effective than using private networks. Companies use the Internet as a virtual backbone for creating a secure virtual link between their corporate offices and remote offices.
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VPN uses a variety of encryption and security mechanisms to make the virtual link secure and to prevent hackers or eavesdroppers from accessing or modifying the data without being detected. VPNs use a technique known as tunnelling to transport encrypted data over the Internet. Tunnelling involves encapsulating one protocol such as IPX, AppleTalk, or IP, encrypting it, and then encapsulating it into IP datagrams. Tunnelling offers the advantage of obscuring the original network layer protocol.
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Figure 55 shows the typical architecture of a VPN:
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Fig. 55 VPN Architecture Creating a VPN Connection
As shown in Figure 55, the following steps are performed to create a VPN connection: 1.
2. 3. 4. 5. 6. 7.
A VPN client dials up to the NAS –Network Access Server, located at the ISP using a Point-to-Point Protocol (PPP) through a PSTN or wireless connection. The NAS communicates with the security server to identify the VPN client. The NAS initiates a communication link using a tunnelling protocol over the Internet to the VPN client's organization gateway. The organization’s gateway decides either to accept or reject the established tunnel from the ISP's NAS. The organization gateway queries the organization security server to confirm the tunnel. Once the tunnel is accepted by the organization gateway, the ISP's NAS logs the acceptance/ traffic. The organization gateway exchanges information such as PPP with the VPN client and assigns the client an IP address.
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A secure tunnel is created between the VPN client and the organization gateway to tunnel the data.
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As mentioned earlier, tunnels are created to permit the VPN client to access their organization’s network. Tunnelling protocols create tunnels and there are different types of PPPs: Point-to-Point Tunnelling Protocol (PPTP) Layer 2 Forwarding (L2F) Layer 2 Tunnelling Protocol (L2TP) IP Security (IPSec) Protocol Suite In addition, the protocols mentioned above could be classified into two categories: 1. 2.
Layer 2 - PFT, L2F, and L2TP are categorised as Layer 2 tunnelling protocols. Layer 3P - IPSec Protocol Suite is a Layer 3 tunnelling protocol.
8.6.5
Firewalls
A firewall is a system that controls access to and from an insecure external network to the local network of an organisation. Firewalls are often implemented at a point where the local network of an organisation connects to an external network such as the Internet. This is often the weakest point since it is vulnerable to an attack. zezenenu.und.lmm/sumeyeqi.en.slo
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Figure 56 shows the Placement of a Firewall in Relation to the Secure Private Network and the Internet:
A firewall at this point will allow all the packets leaving and entering the local network to be examined thoroughly. The examination of packets is defined by the control access policy defined in the security policy of the network. Any packets observed by the firewall to come from an insecure source are discarded. As a result, the risk of an attack on the network is reduced.
8.7
Function of the UMTS Interfaces – A Summary
8.7.1
Radio Access Network
The open interfaces in the UTRAN are Uu and Iu. In addition to these two interfaces, UTRAN contains the Iub (BS - RNC), and the Iur (RNC - RNC) interfaces.
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Fig. 56 Placement of a Firewall in Relation to the Secure Private Network and the Internet
Signaling Protocols Overview
Figure 57 summarizes functions and interfaces of UTRAN:
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Fig. 57 UTRAN Functions and Interfaces
The functions of the RAN are subsets of the management entity Radio Resource Management (RRM). Referring to the UTRAN protocol stack reference model, UTRAN performs different tasks within the transport, control, and user plane. In the transport plane, the most important function is RRC, which contains procedures the set-up, addition, reconfiguration, and deletion of radio links. These procedures are performed both through the Iub and Iur Interfaces. In control plane, the main function is bearer and radio link mapping. In the user plane, the main function is bearer assignment signaling.
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8.7.2
CS and PS Core Network Domains
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Figure 58 summarizes the interfaces in the CN domains:
Fig. 58 UMTS-CN Interfaces
The transport plane in the CN-CS domain is CCS7. In the CN packet domain the transport plane can be ATM, Ethernet, and/or Point to Point Serial connections, with X.25 or Frame Relay on top. The control plane in the CN-CS domain consists of the signaling protocols using the CCS7 stack, which are ISUP, SCCP, MAP, Intelligent Network Application Part (INAP), and Customised Application for Mobile Enhanced Logic (CAMEL). In the CN-PS domain, the control plane is GPRS Tunnelling Protocol (GTP) over User Datagram Protocol/Internet Protocol (UDP/IP). In the CN-CS the user plane is inside the control plane. For example, the control plane protocol ISUP facilitates control plane activity of establishing the connection establishment between the subscribers. The applications of the subscribers can exchange data by using the ISUP facility called User-to-User Signaling (UUS), which is one of the ISUP internal facilities. In the CN-PS domain, the user plane exists and is actually IP carried over GTP over UDP/IP.
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Exercises
Exercise 1 In the below figure, fill in the name of the missing interfaces, transport, and control layers.
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Fig. 59
Exercise 2 Which statement of RAB is NOT true? The RAB carries a connection between the terminal and the core network. The RAB is not a radio link signaling protocol. Voice is the only information on a RAB. Signaling data is the only information on a RAB.
Exercise 3
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Which statement of RRC is TRUE? The RRC is the connection between the terminal and the core network, upon which traffic is transferred. The RRC is the connection between the terminal and radio access network and contains the radio access bearers. The RRC is the connection between the RAN and core network and contains all the RABs from different terminals. The RAB is a radio interface.
Exercise 4 Which statement of ATM connection is NOT true? The Transmission path contains many virtual paths. There is one virtual channel per data subscriber. zezenenu.und.lmm/sumeyeqi.en.slo
One virtual path contains at the most one virtual channel. One virtual path can contain many virtual channels.
Exercise 5 In the RNC, what is the function of the MAC? Selection of data to be inserted in Radio Frame. Selection of common channels. Multiplexing of logical channels to transportation channels. Ciphering for real-time traffic. All of above
Exercise 6 Which statement best describes the function and role of the NBAP protocol? It is the protocol used between the network and the PSTN and used for call set-up purposes.
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It is the protocol used between two RNCs. It is used when one RNC needs to signal a cell in an URA and when performing soft handovers. It is the protocol used between the core network and the RNC and used for the management of resources. It is the protocol used between the RNC and the BTS and used to control the allocation of resources.
Exercise 7 Which statement best describes the function and role of the RANAP protocol? It is the protocol used between the network and the PSTN and used for call set-up purposes. It is the protocol used between two RNCs and used when one RNC needs to signal a cell in an URA and performing soft handovers. zezenenu.und.lmm/sumeyeqi.en.slo
It is the protocol used between the core network and the RNC and used for the management of resource. It is the protocol used between the RNC and the BTS and used to control the allocation of resources.
Exercise 8 Which statement best describes the function and role of the RNSAP protocol? It is the protocol used between the network and the PSTN and used for call set-up purposes. It is the protocol used between two RNCs. It is used when one RNC needs to signal a cell in an URA and when performing soft handovers. It is the protocol used between the core network and the RNC and used for the management of resources. It is the protocol used between the RNC and the BTS and used to control the allocation of resources.
Exercise 9 Which statement best describes the function and role of the ISUP protocol?
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Signaling Protocols Overview
It is the protocol used between the network and the PSTN and used for call set-up purposes. It is the protocol used between two RNCs. It is used when one RNC needs to signal a cell in a URA and when performing soft handovers. It is the protocol used between the core network and the RNC and used for the management of resources. It is the protocol used between the RNC and the BTS and used to control the allocation of resources.
Exercise 10 What is the byte structure of ATM cell? 53 Bytes (48 payload + 5 header) 58 Bytes (50 payload + 8 header)
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53 bytes (45 payload + 8 header) 53 bytes (47 payload + 6 header)
Exercise 11 What is the most significant use of MSS in Release 4? Another up gradation of existing MSC. Calls can be switched at MGW sites without being routed to the MSC server site further increasing transmission efficiency. It can be used for generating CDR. It can be used for transcoding.
Exercise 12 Why ATM is proposed to be used in Release 99 and onwards over presently used conventional PCM links? ATM is cheaper and easier to implement. ATM switches and routers are more stable as compared to the ones presently used
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ATM is cell switching, which has a smaller Byte structure and hence is fast. ATM is packet switching, which is connection less and hence it is fast.
Exercise 13 What is a socket? A combination of the IP address and the port number. A combination of the Source IP and Destination IP address. A combination of the IP address and MAC address. A combination of Source MAC and Destination MAC.
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9.1
Solutions
Exercise 1 (Solution)
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In the below figure, fill in the name of the missing interfaces, transport, and control layers.
Fig. 60
Exercise 2 (Solution) Which statement of RAB is NOT true? The RAB carries a connection between the terminal and the core network. The RAB is not a radio link signaling protocol. Voice is the only information on a RAB. Signaling data is the only information on a RAB.
Exercise 3 (Solution)
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Which statement of RRC is TRUE? The RRC is the connection between the terminal and the core network, upon which traffic is transferred. The RRC is the connection between the terminal and radio access network and contains the radio access bearers. The RRC is the connection between the RAN and core network and contains all the RABs from different terminals. The RAB is a radio interface.
Exercise 4 (Solution) Which statement of ATM connection is NOT true? The Transmission path contains many virtual paths. There is one virtual channel per data subscriber. zezenenu.und.lmm/sumeyeqi.en.slo
One virtual path contains at the most one virtual channel. One virtual path can contain many virtual channels.
Exercise 5 (Solution) In the RNC, what is the function of the MAC? Selection of data to be inserted in Radio Frame. Selection of common channels. Multiplexing of logical channels to transportation channels. Ciphering for real-time traffic. All of above
Exercise 6 (Solution) Which statement best describes the function and role of the NBAP protocol? It is the protocol used between the network and the PSTN and used for call set-up purposes.
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It is the protocol used between two RNCs. It is used when one RNC needs to signal a cell in an URA and when performing soft handovers. It is the protocol used between the core network and the RNC and used for the management of resources. It is the protocol used between the RNC and the BTS and used to control the allocation of resources.
Exercise 7 (Solution) Which statement best describes the function and role of the RANAP protocol? It is the protocol used between the network and the PSTN and used for call set-up purposes.
It is the protocol used between the core network and the RNC and used for the management of resource. It is the protocol used between the RNC and the BTS and used to control the allocation of resources.
Exercise 8 (Solution) Which statement best describes the function and role of the RNSAP protocol? It is the protocol used between the network and the PSTN and used for call set-up purposes. It is the protocol used between two RNCs. It is used when one RNC needs to signal a cell in an URA and when performing soft handovers. It is the protocol used between the core network and the RNC and used for the management of resources. It is the protocol used between the RNC and the BTS and used to control the allocation of resources.
Exercise 9 (Solution) Which statement best describes the function and role of the ISUP protocol?
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It is the protocol used between two RNCs and used when one RNC needs to signal a cell in an URA and performing soft handovers.
Signaling Protocols Overview
It is the protocol used between the network and the PSTN and used for call set-up purposes. It is the protocol used between two RNCs. It is used when one RNC needs to signal a cell in a URA and when performing soft handovers. It is the protocol used between the core network and the RNC and used for the management of resources. It is the protocol used between the RNC and the BTS and used to control the allocation of resources.
Exercise 10 (Solution) What is the byte structure of ATM cell? 53 Bytes (48 payload + 5 header) 58 Bytes (50 payload + 8 header) 53 bytes (45 payload + 8 header) zezenenu.und.lmm/sumeyeqi.en.slo
53 bytes (47 payload + 6 header)
Exercise 11 (Solution) What is the most significant use of MSS in Release 4? Another up gradation of existing MSC. Calls can be switched at MGW sites without being routed to the MSC server site further increasing transmission efficiency. It can be used for generating CDR. It can be used for transcoding.
Exercise 12 (Solution) Why ATM is proposed to be used in Release 99 and onwards over presently used conventional PCM links? ATM is cheaper and easier to implement. ATM switches and routers are more stable as compared to the ones presently used
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Signaling Protocols Overview
ATM is cell switching, which has a smaller Byte structure and hence is fast. ATM is packet switching, which is connection less and hence it is fast.
Exercise 13 (Solution) What is a socket? A combination of the IP address and the port number. A combination of the Source IP and Destination IP address. A combination of the IP address and MAC address.
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A combination of Source MAC and Destination MAC.
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UMTS Services and Applications
UMTS Services and Applications
Contents
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1
Module Objectives.....................................................................................2
2 2.1 2.2
Services and Applications....................................................................... 3 Introduction to Mobile Applications............................................................. 3 Service Platforms........................................................................................4
3
3.3
Services and Applications provided by IP Multimedia Subsystem................................................................................................. 5 Applications Categorisation from the Business Area Point of View .............................................................................................................5 Potential Application Utilising the UMTS Circuit Switched Service.........................................................................................................8 Potential Applications Utilising the UMTS PS Service............................... 8
4 4.1 4.2 4.3
Working of Services: MMS and Streaming Audio & Video ................. 15 Multimedia Messaging Service..................................................................15 Example of MMS Flow .............................................................................. 19 Streaming Audio and Video in UMTS Network ........................................ 24
5
Virtual Home Environment..................................................................... 26
6
Appendix.................................................................................................. 27
7 7.1
Exercises..................................................................................................28 Solutions....................................................................................................31
3.1 3.2
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1
Module Objectives
The aim of this module is to give the student the conceptual knowledge needed for explaining the GSM and UMTS mobile applications. Topics to be covered in this module include the differentiation between UMTS services and applications, a general discussion of the Virtual Home Environment, and an introduction to the most important service platforms. After completing this module, the participant should be able to:
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List the services and applications UMTS network provided. List the services and applications that IP Multimedia System provides. List the GSM services that can still be supported in the UMTS networks. Explain briefly working of Short Message Service, Multimedia Messaging Service, and audio and video streaming.
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Services and Applications
2.1
Introduction to Mobile Applications
In your everyday life, you are familiar with the concept of a mobile application. For example, a mobile phone call is a mobile application. An SMS is another type of mobile application. With time, the need for different types of applications is increasing. Today the subscribers expect an increased number of applications and greater value. For an operator with a large subscriber base, more usage time is one way of ensuring continuing growth. However, the subscribers use mobile rd applications on for a limited time. Therefore, when defining the 3 Generation (3G) specifications, the emphasis is on the unlimited prospect of seamless services and applications that can be provided. One common misconception that people have is that applications have been introduced in UMTS. However, this is not true as GSM already offers both integrated network and Intelligent Networks (IN) applications. In today's networks, General Packet Radio Service (GPRS) adds the facility of supporting packet data with relatively quick set-up and transfer times, such as in the case of Internet. zezenenu.und.lmm/rolawexu.en.slo
UMTS Services The term mobile application refers to services provided to the subscriber. Mobile applications have not been standardized in UMTS. The GSM/UMTS network offers service elements that are used by applications. The applications form the value added for the subscriber. A set of services have been made available by UMTS, which are: Circuit Switched (CS) Services - These are the teleservices, such as speech call, facsimile call, and CS data. Packet Switched (PS) Services - These are based on the PS connectivity provided by Packet Data Protocol (PDP) contexts. Message Services - These include Short Message Service (SMS) and Multimedia Message Service (MMS). The services speech call, facsimile, and SMS are both services and applications. CS data is only a service because the subscriber allocated with a CS bearer for data transport. The bearer itself adds no value to the subscriber. The subscriber requires the CS data bearer to run a data application, where content is for instance exchanged between two entities, for example, between the handheld device and an application related content server. The same is true for PS services that are used to establish a PS bearer. Again, the PS bearer alone adds no value to the subscriber. However, when the subscriber can use the bearer in combination with an application, then value is added for the subscriber For example, a subscriber can use a PS bearer between the handheld device and the Internet to gain content through the application HTTP and TCP/IP.
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Consequently, the GSM/UMTS services must be selected in such a way, that the application running on top of it can be served in the best possible way.
2.2
Service Platforms
Service platforms are entities, which offer the implementation methods for applications. A service platform is a logical entity often containing several pieces of equipment. Following are the majority of existing applications till December 2002 were adopted from GSM: 1. 2.
Voice Mail System (VMS) for Voice Call Completion. Service delivery platform enabling servers that support different types of applications. A typical example is the Short Message Service Centre (SMSC) for short message delivery.
3.
Service creation and execution platform is built upon the principles of IN and is almost obligatory to provide the envisioned services.
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Figure 1 shows the elements of Core network service platform:
Fig. 1 Core network service platform elements
The new WCDMA radio interface will improve the quality and convenience of these applications. It will also enable higher packet data rates, which is highly important for the new e-mail and Internet services. The circuit connections can initially be made to the GSM switches to provide speech and other circuit switched services of up to 64 Kbps.
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Services and Applications provided by IP Multimedia Subsystem
3.1
Applications Categorisation from the Business Area Point of View
The different potential applications can be categorized into five distinct groups as follows: 1. 2. 3. 4. 5.
Person-to-Person multimedia communications Mobile Internet Business solutions Mobile commerce Location-based services
Although it is difficult to predict the services that will be the most popular, it is anticipated that the services working together will be more in demand. zezenenu.und.lmm/rolawexu.en.slo
Figure 2 shows the Using a Multitude of Services:
Fig. 2 Example of Using a Multitude of Services
Figure 2 shows the use of searching based on location to find a theatre. The mobile network allows subscribers to make an instant reservation. This feature is called the NSN mCommerce solution. As the subscriber travels to the chosen theatre, the mobile network provides a map application, assisted with location-based services suggesting the means of traveling towards the destination. Finally, the subscriber updates a Personal Information Management (PIM) application with the information of the travel and theatre.
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3.1.1
Person-to-Person Multimedia Communications
Person-to-person communications is the interaction and sharing of end-subscriber created information between the individuals. Currently, person-to-person communication is mainly related to voice calls and SMS. In 3G, person-to-person communications will evolve to provide new types of messaging and telephony services, which will include the following: Chat from one to many. Calendar and e-mail including synchronization. Rich call and video telephony. Picture messaging and multimedia messaging. Evolution of messaging will bring richer content into the messages. With multimedia messaging, it is possible to combine the conventional short messages with richer content type, such as photographs, images, and video clips. In addition, it is not only possible to send messages from one hand set to another but also from handset to e-mail.
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Figure 3 shows the development of person-to-person messaging:
Fig. 3 Development of Person-to-Person Messaging
During the month of June 2001, around 20 billion SMSs were sent globally. In September 2002, 27 billion of them were sent. During 1999 and 2000, in Norway, there was an increase of 1000% SMSs. In Italy, there was an increase of 700% SMSs in 7 months.
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3.1.2
Mobile Internet
The introduction of Wireless Application Protocol (WAP) has shaped the mobile industry into a direction where mobile technology is combined with the Internet. The added value provided by Mobile Internet as opposed to fixed Internet can be summed up with four key words as follows: 1. 2. 3. 4.
Personalized, which means always relevant to me. Available, which means wherever I need it. Immediacy, which means information when I need. Real time, which means latest version, as soon as it happens.
Figure 4 shows an example of how the Mobile Internet can be used for a subscriber's life style. The categories of services can be divided into information and entertainment:
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Fig. 4 Mobile Internet Services
There is a misconception that the Mobile Internet services are only introduced in UMTS. However, there are no limiting factors currently to stop the operator or the content provider from introducing these services. Although in CS networks, there are few limitations in terms of speed and connection set-up. The advantage of GPRS should overcome or reduce these limitations.
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3.2
Potential Application Utilising the UMTS Circuit Switched Service
3.2.1
Potential Applications
Applications are the end subscriber services. They are no longer standardized. It is up to operators and value-added service providers to determine the need for an application and implement them. GSM/UMTS offer the bearer and call control to exchange content and content-related signaling information between the mobile device and the application driven content server.
News and traffic flashes Public video phoning Ticketing services and interactive shopping Desktop video conferencing Voice recognition and response Interactive and virtual school Universal SIM with credit card function Virtual banking Currency downloading Video-on-demand Online library and books In addition to the applications listed above, the supplementary services used in GSM are available from the very beginning of the 3G.
3.3
Potential Applications Utilising the UMTS PS Service
One of the main reasons for the implementation of UMTS networks is the anticipated demand for data services. There are different types of PS services and requirements for the services.
3.3.1
Voice Over IP
The well known use of voice telecommunication is telephony speech, for example, GSM, but with Internet and multimedia, a number of new applications, for example Voice Over IP(VoIP) and video conferencing tools, will require this scheme. Real-time conversation is always performed between peers or groups of live or human end-subscribers. This is the only scheme where the required characteristics are strictly given by human perception or senses.
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The applications that have been planned for the implementation of GSM/UMTS are as follows:
UMTS Services and Applications
3.3.1.1 Push to Talk Over Cellular (PoC) PoC is a direct, real-time voice communications service. The principle of this service is to just push to talk. The calls can be started to both individuals and groups with just a push of a key because of a direct connection. The half-duplex or the one way at a time, call connection is almost instant. This technology uses the capabilities of the IP Multimedia Subsystem (IMS) as specified by 3GPP. PoC is based on a half-duplex, always-on VoIP service over the second generation GSM/GPRS network. Push to talk uses the Session Initiation Protocol (SIP) service architecture as SIP messaging, which makes new applications, such as voice chat and group chat messaging possible. Groups can also be created using SMS, which is familiar and easy to control for the subscriber.
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3.3.1.2 Voice and Video Over IP Videophone implies a full-duplex system, carrying both video and audio, and is intended for use in a conversational environment. For this technology, the same delay requirements as for conversational voice will apply. The added requirement is that the audio and video must be synchronized within certain limits to provide the lip-synch, which means the synchronization of the speaker’s lips with the words being heard by the end-subscriber. Due to the long delays in even the latest video codecs, it will be difficult to meet these requirements. The human eye is tolerant to some loss of information therefore, certain degree of packet loss is acceptable depending on the specific video coder and amount of error protection used. It is expected that the latest video codecs will provide acceptable video quality with frame erasure rates up to 1%. Figure 5 shows video telephony:
Fig. 5 Video Telephony
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3.3.1.3
Point-to-Multipoint, Multicast via Serving GPRS Support Node (SGSN) When the subscriber is looking at a video or listening to audio, the scheme streams apply. The real-time data flow is always aiming at a live or human destination. It is a one-way transport called unidirectional continuous stream. This scheme is new the world of data communication, which gives rise to a number of new requirements for telecommunication and data communication systems. Audio streaming is expected to provide better quality than conventional telephony, and requirements for information loss in terms of packet loss will be tighter. Similar to voice messaging, there is no conversational element involved and delay requirements are flexible even more than for voice messaging. An example of audio streaming is the web radio station.
3.3.2
Data
Although there may be some exceptions, it is assumed that from a subscriber’s perspective the prime requirement for any data transfer application is to essentially guarantee zero loss of information without any delay variation. Therefore, the applications tend to distinguish themselves on the basis of the delay that can be tolerated by the end-subscriber from the time the source content is requested until it is presented to the subscriber. The Release 5 feature High Speed Downlink Packet Access (HSDPA) provides a similar boost for WCDMA that EDGE does for GSM. It provides a two-fold increase in air interface capacity and a five-fold increase in data speeds in the downlink direction. In addition, HSDPA shortens the round-trip time between the network and terminals and reduces variance in downlink transmission delay.
3.3.2.1 Web Browsing In this category, we will refer to retrieving and viewing the HTML component of a web page. Other components, for example, images, audio, or video clips, are dealt with under separate categories. From the subscriber’s perspective, the main performance factor is how fast a page appears after it is requested. A value of 2 to 4 seconds per page is proposed. Mobile browsing delivers formatted Web pages to the subscriber’s terminal and displays them on the screen, enabling interaction with active elements on the page, such as links and forms. In the case of pull, the subscriber consumes the product by clicking links and form buttons to request the next page. Mobile browsing also supports push, which is an action initiated by the server to deliver
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The main distinguishing feature of one-way video is that there is no conversational element involved, which means that the delay requirement is not be very stringent, and can follow that of streaming audio. An example of one-way video is monitoring your home using the Internet.
UMTS Services and Applications
content to the terminal. subscribers may receive a Service Initiation push message, asking for permission to display a page, or a Service Load push message, which depending on the subscriber settings, can automatically load a page and then display it, or simply have it ready in the cache for immediate display later.
3.3.2.2 Interactive Games Requirements for interactive games depends on the specific game, but the demanding applications require short delays and a value of 250 ms, which is consistent with demanding interactive applications, is recommended.
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Figure 6 shows the interactive gaming:
3.3.2.3 High-Priority Transaction Services or E-commerce The main performance requirement in the High-Priority Transaction Services, such as e-Commerce is to provide a sense of immediacy to the subscriber that the transaction is smooth. A value of 2 to 4 seconds is suggested to be acceptable to most subscribers. A mobile wallet in the terminal can improve the convenience of mobile commerce significantly. By providing local storage of payment and access credentials and support or federated identity technologies, such as Liberty, the terminal wallet reduces the number of actions required by the subscriber during a browsing session. Instead of the consumer remembering and typing payment card numbers and access profiles, such as PINs and passwords, the mobile wallet can provide them to the service provider automatically through an intuitive subscriber interface. In addition, a mobile wallet can extend this automation to shipping address information that is otherwise entered manually. Lifecycle management can be facilitated by Over-The-Air (OTA) provisioning of the credentials to be stored in the mobile wallet. Instead of the subscriber keying in the data manually, the data can be received over-the-air, for example, credit card details from the card issuer over-the-air.
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Fig. 6 Interactive gaming
UMTS Services and Applications
Credentials storage is secure and protected by terminal security architecture and a password. In future, the mobile wallet can include support for operator-based payment services, such as server -wallets and premium SMS, new card association technologies for browser-based payments, such as 3D secure, and an open development environment.
3.3.2.4 Two-Way Control Telemetry Two-way control telemetry is an example of a data service that requires a real-time streaming performance. The two-way control implies a low allowed delay. The proposed value is 250 ms, but a key difference between the voice and video services in this category is the zero information loss tolerance, required for certain processes, for example, controlling important industrial processes. It will become possible for many machines will be able to communicate with each other. For example, an ice-cream vending machine can tell the supplier that it is running out of chocolate cones, enabling the vending operator to better schedule his onsite visits. Similarly, an electricity meter can send consumption figures to the to the billing system of the energy provider, therefore, enabling increased frequency of meter reading. It will also be possible to activate the alarm system at a cottage remotely, check if the doors at your home are locked, or tell your greenhouse to water your plants using your mobile handset. zezenenu.und.lmm/rolawexu.en.slo
3.3.2.5 E-mail or Server Access E-mail is thought to be a store and forward service, which can tolerate very long delays. However, it is important to differentiate the communications between the subscriber and the local e-mail server and server-to-server transfer. When the subscriber communicates with the local mail server, the expectation is that the mail may not be transferred instantaneously but will definitely be transferred rapidly. The proposed time is 2 to 4 seconds for the transfer, which is consistent with the research findings on delay tolerance for web browsing. Figure 7 shows an electronic postcard:
Fig. 7 Electronic Postcard
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3.3.2.6 Voice Messaging and Dictation Requirements for information loss are similar as for conversational voice with the key difference that in voice messaging and diction, there is more tolerance for delay because there is no direct conversation involved. Therefore, the main issue is the amount of delay that can be tolerated between the subscriber issuing a command to replay a voice message and the actual start of the audio. There is no precise data on this, but a delay of a few seconds can be tolerated. 3.3.2.7 Presence Presence is a familiar concept for the subscribers using instant messaging services on the fixed Internet. In mobile phones, presence will not only enhance messaging but will introduce a service that can be used in many other applications and services. It will be at the center of all communication technologies and mobile telephony will benefit from the presence information. Instant messaging is the first presence-enabled application that utilizes presence information in the presence server of the operator.
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Figure 8 shows the presence groups:
Fig. 8 Presence Groups
Presence can be defined as a dynamic variable profile of the subscriber, which is visible to others and is used to represent oneself, share information, and control services. Presence represents a the status of the subscriber to others and the status of others to the subscriber. Status may contain information, such as personal and device status, location or context, terminal capabilities, and preferred contact method.
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4
Working of Services: MMS and Streaming Audio & Video
4.1
Multimedia Messaging Service
The MMS Evolution SMS is currently the most successful data service in GSM. In September 2002, more than 27 billion SMS messages were transmitted. It is expected that the SMS messages transmitted will further increase. In the year 2002, about 11% of the income of an operator comprised the earnings from the short message service.
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Nokia was the first handheld supplier to use the SMS infrastructure for another application. Instead of sending text messages, download of simple pictures or ringing tone became possible with Nokia Smart Messaging phones. Smart messaging enabled the subscribers to personalize their messages to a higher degree. The great success of Smart Messaging resulted in a standard for enhanced SMS capabilities: Enhanced Message Service (EMS), which was developed by the 3GPP. EMS allows the transmission and reception of ring tones, sounds, animations, and simple pictures. The subscriber can even create own pictures and tones. EMS supports both phone personalization and person-to-person messaging. The main advantage of EMS from the perspective of the operator is that no investment is required in an EMS infrastructure. EMS is based on and uses the existing SMS infrastructure. MMS was specified with UMTS Release 4. During the specification process, the 3GPP worked with several assumptions. One assumption was that the potential transmission rates will be higher than in the second generation, therefore, allowing a higher data rate and more flexible bearer allocation. Another assumption was that many mobile phones will have colored screens and higher resolution than earlier models. With the new options for bearers and terminal capabilities, the aim was to specify a more advanced option for transmitting pictures, music, text, and video. Therefore, MMS was specified to allow the transmission of larger messages, containing a wide range of content. MMS supports person-to-person communication, and allows both the service providers and subscribers to generate content.
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Figure 9 shows the evolution of short message:
Fig. 9 Short Message Evolution
A Multimedia Messaging Service (MMS) message can be compared with a standardized envelope, in which neither the content nor size was specified. The MMS message is represented by a standardized presentation language, Synchronized Multimedia Integration Language (SMIL). A SMIL page holds information on how, where, and when to display the different multimedia elements. The media elements, such as pictures, text, and sound, are combined into a single message, using Multipurpose Internet Mail Extension (MIME). MIME is a standard, which specifies how several media are placed within a message. In the Internet, the message is the email and in the mobile network, it is the MMS message. A wide range of media types are supported, such as audio, for example, video, for example, MP4, text, for example, ISO-8859-1, and pictures, for example, baseline JPEG. Several mobile phone manufactures have agreed in supporting a minimum set of media types to guarantee interoperability.
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The MMS Message
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Figure 10 shows the MMS envelope:
Fig. 10 MMS Envelope
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MMS Today Since December 2002, more than 40 operators have already started the commercial launch of MMS. Currently, the GPRS infrastructure is in use for the MMS transport. Now, MMS over WAP is the common method to transfer MMS message, but the MMS specified is independent from the WAP. Therefore, other means of MMS transport may be possible in future MMS Architecture The MMS architecture consists of several network entities. Some of the entities can be combined within a single network element. MMS UE MMS is based on the client server principle. A MMS UA can reside on the mobile equipment, but can be also made available on external devices, such as laptops, and PDAs. These external devices can be connected to a UE to use MMS through the radio interface. However, due to the way MMS was specified, it can also be deployed on a fixed network personal computer. The MMS UE interacts with the Multimedia Message Service Environment (MMSE). The MMSE incorporates MMS service elements, which are responsible for the delivery and storage of MMS messages. The MMSE entities are the as follows: MMS Server -This network entity is responsible for managing incoming and outgoing messages. It is also used for MMS storage.
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MMS Relay -This network element is responsible for the interworking between different messaging systems and Charging Data Record (CDR) generation. It can be connected to voice mail servers, E-mail servers, and Fax servers. Although MMS Server and MMS Relay were specified as two individual network entities in UMTS Release 4. Most vendors offer their functionalities in one network element. In NSN, the network element is called MMS Server or Relay MMS Center. Currently, MMS over WAP is the common method to transfer MMS message, but MMS is specified independent of the WAP. Therefore, other means of MMS transport may be possible in future
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Figure 11 shows the MMSC including its reference points, MM1 to MM8. The reference points are not open and only the format of the subscriber data is specified. Reference point MM2 is between the MMS Relay and the MMS Server:
Fig. 11 MMS Center and Reference Points
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4.2
Example of MMS Flow
4.2.1
UE to UE MMS Transfer
In this example, an MMS transfer between two UEs is outlined. The assumption is that the multimedia messages are transmitted through WAP. Before multimedia messages can be exchanged, MMS related signaling between the MMS UA and the MMS Center must take place. To transmit the signaling information, a bearer is required between the UE and the MMS Center. In the example, a bearer is made available through the PS domain. A PDP context between the UE and the external PDN WAP was established. This bearer is used to transmit MMS messages over WAP. The sequence of events that follow are as follows:
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1. The UE invokes a Wireless Session Protocol or Hypertext Transfer Protocol Power On Self Test (WSP/HTTP POST) operation with the M-Send.req message embedded as the content body. This message is submitted using a Uniform Resource Identifier (URI) that addresses the MMS Center that supports the specific terminal. The UE composes a transaction ID for the submitted message. This ID is used by the UE and the MMS Center to provide linkage between the originated M-Send.req and the response M-Send.conf messages. The value used for the transaction ID is determined by the UE, and no interpretation is expected from the MMS Center. 2. The MMS Center assigns a message ID to the message when successfully received for delivery. The ID is used in activities that need to refer to the specific sent message, for example, sending the possible delivery report later. Upon receipt of the M-Send.req message, the MMS Center responds to the WSP/HTTP POST with an answer that includes the M-Send.conf message in its body. Body means the HTTP level payload. The response message provides a status code for the requested operation. If the MMS Center is willing to accept the request to send the message, the status is accepted and the message includes the message-ID composed by the MMS Center.
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Figure 12 shows the step 1 and step 2 for UE to UE MMS over WAP:
3. The headers of the PDU, which are the headers added by the MMS Center of the sender to the original PDU, are used to generate a notification to the recipient, and are delivered with the message body parts to the recipient at retrieval. The MMS Center creates a transaction identifier before sending the notification. The identifier is unique up to the following M-NotifyResp only. If the MMS Client requests deferred or delayed delivery with M-NotifyResp, the MMS Center may create a new transaction identifier. The notification uses SMS as bearer and the MMS Center sends the M-Notification.ind to the SMS Center. The SMS Center further forwards the message to Short Message Service Gateway Mobile Switching Centre (SMS-GMSC). The SMS-GMSC asks for the routing info from HLR. For example, the location of the MSC that the recipient UE was last connected with or the SendRoutingInfoForShortMs and then, the SMS-GMSC forwards the message to MSC or the ForwardShortMessage. After receiving the message, the MSC checks VLR to make sure that the UE has not been barred or otherwise restricted from using the network or the SendInfoForMT-SMS. Finally, the MSC forwards the message through the BSS to the receiving UE.
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Fig. 12 UE to UE MMS over WAP -Step 1 and Step 2
UMTS Services and Applications
4. The information in M-Notification.ind includes the URI that will be used to retrieve the message in a subsequent operation by the receiving terminal. The terminal may use additional information about the message, for example, message size or expiry, to determine its behavior. The UE may delay the retrieval of the message if it exceeds a defined size. The receiver of the M-Notification.ind informs the MMS Center with the M-NotifyResp.req about the action to be taken to, which is routed to the MMS Center the same way as the M-Notification.ind. Figure 13 shows the step 3 and step 4 for UE to UE MMS over WAP:
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Fig. 13 UE to UE MMS over WAP - Step 3 and Step 4)
5. The URI of the MMS Center address required for the retrieval, sent in the preceding M-Notification.ind message, is used in the GET request. 6. The data returned or the M-Retrieve.conf includes the multimedia message. The header component provides additional information, such as the tariff class, which is useful in AT messages. 7. The MMS Center may decide to request an acknowledgement from the UE to confirm the delivery status of the retrieval based on whether it needs to provide a delivery notice back to the originating UE or not. Alternatively, the MMS Center may request and acknowledgement to be able to delete the message from its own store after the successful delivery.
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Figure 14 illustrates the step 5, 6, and 7 for UE to UE MMS over WAP:
8. The MMS Center sends the M-Delivery.ind message to the originating MS using WAP PUSH to inform when the message is delivered. The Message ID identifies the message and is generated when the original message is posted. It also provides addressing information of the originally targeted entity. 9. M-read-rec.ind message is sent by the receiver’s UE to the MMS Center to inform when the receiver has opened the message. 10. The MMS Center sends the M-read-orig.ind message to the originating MS using WAP PUSH to inform when the receiver opens the message.
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Fig. 14 UE to UE MMS over WAP - Step 5, 6, and 7
UMTS Services and Applications
Figure 15 illustartes the step 8, 9, and 10 for UE to UE MMS over WAP:
Fig. 15 UE to UE MMS over WAP - Step 8, 9, and 10) zezenenu.und.lmm/rolawexu.en.slo
E-Mail and MMS E-Mails are nowadays a popular means of communication. The example explains the mobile E-mail transfer using MMS. The MMS Center or MMS Relay functionality converts the Mobile Message (MM) to an E-mail message and sends it to the Mail Server. The communication between Mail Gateway (GW) and Mail Server is based on Simple Mail Transfer Protocol (SMTP) or MIME protocol. SMTP understands only pure text based data and is used for the actual data transfer. MIME is used for attachment support. The Mail Server acknowledges the receipt of message to the MMS Center. This acknowledgement belongs to the SMTP protocol.
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Figure 16 show the E-mail Connectivity:
4.3
Streaming Audio and Video in UMTS Network
4.3.1
Video Call and Video Services
The mobile video services will possibly evolve from the current multimedia messaging of still and animated pictures and presentations, to video messaging and playback. Video download and video streaming services will shortly follow. The time for introducing these services will differ from country to country. NSN believes “See What I See” (SWIS). Therefore, video telephony and broadcasting will be interesting applications in the future.
4.3.2
Video Telephony
Video Telephony refers to making or receiving a video call when the mobile subscriber can see as well as talk to the other person. It allows the subscriber both visual and verbal communication. The conversation experience can be further improved by allowing one or both subscribers to see what the other person sees. Therefore, it is possible to not only see each other but a general concept of sharing is allowed.
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Fig. 16 E-mail Connectivity
UMTS Services and Applications
The display of mobile devices, including screen size, resolution, and local memory, makes mobile video content different from content of other media. As a result, it essential to design the content to suit the mobile device and the method of distribution. In order to ensure that video services take off, a vast database of video content must be developed. Then, the database needs to be constantly improved with new ideas and substance. The video formats in which the video rd content has been encoded, such as the open standards 3 Generation Partnership Project (3GPP) file format, can be used throughout the evolution of video services.
4.3.3
Video Download
As the name implies, video download refers to the delivery of video clips to a mobile device. This is usually through discovery such as browsing and then followed by a WAP or Transmission Control Protocol/Internet Protocol (TCP/IP) session where the clip is sent to the device to be viewed or stored. Digital rights management defines the usage rules for commercial quality content, while the available memory capacity of the device determines the storage possibilities
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In video downloading, the wireless profile of TCP/IP is the key enabler downloading large files. Although large video files can be downloaded over the WAP stack, the download is faster with the same network bandwidth if the transfer is done over the TCP/IP stack. This reduces the waiting time while the file is being delivered from a server to the subscriber’s device. The evolution of the underlying network to Enhanced Data Rates for GSM Evolution (EDGE) and Wideband Code Division Multiple Access (WCDMA) will secure capacity and cost-effectiveness. Roaming agreements between operators are required.
4.3.4
Video Streaming
Video Streaming indicates immediate consumption of on-demand or live video content on a mobile device. It allows the consumption of large video files with no dependence on the device memory because the file or content is not physically stored on the client device. This method can be compared to the broadcast model of watching television programs. Control of Quality of Service (QoS) is needed in the radio access and core network to ensure that video applications work properly. This can be done by network dimensioning and configuration, which ensures sufficient capacity for streaming subscribers. Earlier the GPRS networks were based on best effort, where capacity is shared evenly among the subscribers in a cell. In WCDMA and EGPRS networks, it is possible to provide the subscriber with a guaranteed bit rate for good service performance.
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5
Virtual Home Environment
Virtual Home Environment (VHE) is a concept for personal service environment portability across network boundaries and between terminals. The purpose of VHE is that subscribers should consistently be presented with the same personalized features in any terminal, any network, and any location. User interface customization and services should be provided in a seamless manner between networks and terminals, within the capabilities of the terminal and the network. Currently; Customised Applications for Mobile network Enhanced Logic (CAMEL), Mobile Execution Environment (MExE), Open Systems Architecture (OSA), and Universal SIM Application Toolkit (USAT) are the mechanisms supporting the VHE concept. Each application toolkit has a specified application execution environment. The application execution environment is used to run specific, non-standardized applications. The options to personalize applications exist. The application toolkits for operator specific services are USAT, MExE, and CAMEL. The VHE can be viewed both from the subscriber perspective and network perspective. The home environment allows a subscriber to personally perform management operations on one or more subscriber profiles, such as activate, modify, and deactivate. The network side of VHE; (the Home Environment and Home Environment –Value Added Service Provider) is also able to manage one or more subscriber profiles. The VHE from a network point of view is designed to be able to provide and control services to the subscriber in a consistent manner, even in cases when a subscriber is roaming. It also has to facilitate creation and maintenance of a set of subscriber profiles. In addition, it has to support the execution of services through its Service Toolkits in the network, the Universal Subscriber Identity Module (USIM) and in the ME. The VHE must also be able to uniquely identify the subscriber in any of the telecommunication networks supported by the Home Environment.
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With GSM systems, one obvious drawback related to roaming was the portability of the subscriber services. To increase the value added to the subscriber and consequently the potential to earn revenue for the operator, a wide range of personalized services are expected. If a large set of diversified applications that are not specified exist, a framework has to be designed to enable seamless application provisioning between networks. From the subscribers’ point of view, the applications should be always available, regardless of the location of the subscribers, and the application should be presented to the subscribers in the same way as if they are in their home PLMN.
UMTS Services and Applications
6
Appendix
mCommerce NSN believes that mobile phones will become the personal trusted device that enables mCommerce. With UMTS, the type and variety of mCommerce transactions increases significantly, becoming a way of life for every day needs. Some examples of every day needs are local payments, online banking, music purchases and downloads, and ticketing. Also advertising will become an important part of overall mCommerce. Trust on a brand for providing the mCommerce service and transaction security are two essential factors ensuring the acceptance and growth of mCommerce. NSN's mCommerce solution addresses the following three key elements of secure transactions: 1. Confidentiality, meaning those contents of the transaction can not be seen by any outsider. 2. Integrity, meaning that the parties performing the transaction can be sure that the other party is the one he/she claims. zezenenu.und.lmm/rolawexu.en.slo
3. Irrevocability, meaning that either party after performing the transaction cannot claim that the transaction has not been performed. Figure 17 shows example where mCommerce can be used:
Fig. 17 Examples of mCommerce Usage
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7
Exercises
Exercise 1 Identify the UMTS services provided in the UMTS network? (Choose three) CS Data Services Web browsing SMS Speech call VoIP call VMS
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Exercise 2 Identify the operator specific services? (Choose two) Cell Broadcast Service PS service SAT CAMEL
Exercise 3 For which network element, the USAT specify open Application Programming Interface (API)? SIM and ME SIM and a remote application server SIM and SCP ME and RNC
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Exercise 4 What is the primary goal for developing WAP/WTA? To exclusively support MExE To design and program applications locally on the ME To allow interaction between the SCP and the ME To support radio interface protocols
Exercise 5 The abbreviation OSA stands for Open Systems Architecture. True False zezenenu.und.lmm/rolawexu.en.slo
Exercise 6 Which statement best describe a bearer channel? A traffic channel only for speech A signaling channel between the core network and the radio access A variable channel that can carry different types of data A fixed-bit-rate data channel
Exercise 7 Which two are characteristics of Virtual Home Environment (VHE)?(Choose two) Allows the subscribers to use their services whilst roaming The subscribers can customize their own environment It is the same as a SMSC VHE is possible because of CAMEL VHE is located within the HLR
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It is only possible in UMTS
Exercise 8 Which statement of Location Services is TRUE? Can be offered only in combination with a subscription to basic telecommunication services Are a prerequisite for roaming Are used for determining the position of the mobile terminal
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Location Based Services have the same meaning
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7.1
Solutions
Exercise 1 (Solution) Identify the UMTS services provided in the UMTS network? (Choose three) CS Data Services Web browsing SMS Speech call VoIP call VMS
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Exercise 2 (Solution) Identify the operator specific services? (Choose two) Cell Broadcast Service PS service SAT CAMEL
Exercise 3 (Solution) For which network element, the USAT specify open Application Programming Interface (API)? SIM and ME SIM and a remote application server SIM and SCP ME and RNC
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Exercise 4 (Solution) What is the primary goal for developing WAP/WTA? To exclusively support MExE To design and program applications locally on the ME To allow interaction between the SCP and the ME To support radio interface protocols
Exercise 5 (Solution) The abbreviation OSA stands for Open Systems Architecture. True
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False
Exercise 6 (Solution) Which statement best describe a bearer channel? A traffic channel only for speech A signaling channel between the core network and the radio access A variable channel that can carry different types of data A fixed-bit-rate data channel
Exercise 7 (Solution) Which two are characteristics of Virtual Home Environment (VHE)?(Choose two) Allows the subscribers to use their services whilst roaming The subscribers can customize their own environment It is the same as a SMSC VHE is possible because of CAMEL VHE is located within the HLR
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It is only possible in UMTS
Exercise 8 (Solution) Which statement of Location Services is TRUE? Can be offered only in combination with a subscription to basic telecommunication services Are a prerequisite for roaming Are used for determining the position of the mobile terminal Location Based Services have the same meaning
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NSN Products
NSN Products
Contents
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1
Module Objectives.....................................................................................3
2 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8
The NSN UMTS Core Network Solution..................................................4 NSN UMTS Core Network .......................................................................... 6 Packet Switched - PS Domain..................................................................19 GPRS Evolution For 3G ............................................................................ 19 Flexi ISN 3.2 ..............................................................................................25 IP Multimedia Subsystem..........................................................................28 Push-To-Talk Over Cellular (PoC) System Architecture...........................29 Intelligent Content Delivery ....................................................................... 30 NSN Intelligent Enhanced Data Rates for GSM Evolution....................... 33
3 3.1 3.2 3.3
NSN UTRAN Solution..............................................................................35 Radio Network Controller (RNC) ...............................................................35 NSN Base Station Solutions..................................................................... 43 NSN Site Solutions and Transmission...................................................... 57
4 4.1 4.2 4.3
UMTS Network Management Solutions................................................ 61 NSN NetAct Solution .................................................................................63 NSN Element Management Tools.............................................................65 NSN Network Management Functions ......................................................66
5 5.1
Exercises..................................................................................................70 Solutions....................................................................................................74
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1
Module Objectives
The aim of this module is to give the student the conceptual knowledge needed for explaining the UMTS Core Network Solution, Packet switched domain, UTRAN solution, UMTS network management solutions. After completing this module, the participant should be able to: Explain how base station sites are selected. Identify the different cellular transmission solutions available. Identify the main functions of a Radio Network Controller (RNC). List and identify the network elements used within the core network in terms of the name and function within the context of Release 99. List and identify the need for comprehensive network management in UMTS. Identify the framework of the Nokia Siemens Networks (NSN) NetAct solution.
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2
The NSN UMTS Core Network Solution
The NSN network elements are built on a reliable and proven carrier class platform. This is designed to ensure flexible and fault-tolerant implementation. The platform comprises two basic components, the hardware and the software. The physical equipment is usually distributed across a geographical area. For example, base stations can be found on top of roofs, in the fields, and inside the buildings. The larger equipment are usually located together in a secure building. Network elements are connected together using standard transmission technology often through 3rd party suppliers.
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Figure 1 shows NSN network platform:
Fig. 1 NSN Network Platforms
There are four main platforms that are used in the Third Generation Universal Mobile Telecommunications System (3G/UMTS) network: 1.
2.
3.
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DX200 Platform - The NSN GSM elements are based on this proven CS technology or Mobile Switching Center (MSCi), SGSN Combi, and Flexi SGSN. IPA2800 Platform - IPA2800 is the new distributed computing platform upon which the new 3G/UMTS network elements, for example, RNC, are built. Unlike the DX200 platform, the IPA2800 has PS architecture with an ATM switch. NSN Internet Protocol (IP) Platform - The NSN IP core network elements, for example, 3G SGSN and GGSN are built on a solid IP based platform.
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NSN Products
4.
UNIX HP/SUN - The network management and service provisioning systems are built on industrial server platform, using proven operating systems like UNIX. The NSN software is installed on the operating system.
For platforms, the other aspects to be taken into account are as follows: Local graphical interface - Network Element Management Unit (NEMU) The NSN 3G/UMTS network solution uses a graphical environment that can be accessed through the Internet as its primary interface. Network Management System (NMS) interface - For efficient management, a single interface is used to perform network management functions for the network elements. For example, a single alarm monitor is used to monitor faults generated by network elements. NSN online services - To support the 3G network elements, NSN offers access to documentation, change notes, and technical notes on the equipment through the Internet. NSN Online Services (NOLS) is an integral part of the platform solution.
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NSN Products
Figure 2 shows the different types of interfaces used in the NSN solution:
2.1
NSN UMTS Core Network
The Core Network (CN) consists of two domains, CS and PS. Currently, the networks are usually a combination of both; however, the IP Telephony (IPT) network are being used increasingly. Voice call services in 3G mobile networks will first be based on CS logic with UMTS Release 99. GSM operators will be offered an evolutionary way of upgrading their networks, including dual-mode operation with GSM. When from any pre-existing GSM network to a UMTS Release 99 network, operators try to ensure that previous investments are efficiently utilized and the new investments are minimized. In this chapter, you will look at both domains of the CN. All the conceptions you are going learn in this chapter are based on UMTS Release 99.
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Fig. 2 Different Types of Interfaces Used in the NSN Solution
NSN Products
In this chapter, there are two new elements introduced are the NSN Media Gateway (MGW) and the 3G-SGSN. They are based on new platforms and have a few new functions as well. Figure 3 shows a CN, which is the building block for the network:
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Fig. 3 CN - Building Block for the Network
Fig. 4 The NSN MSC
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NSN Products
Transcoding in UMTS networks takes place in the CN. NSN implements the transcoders just before the visited MSC. If the transcoders were located in the Gateway MSCs, handovers between UMTS and GSM cells would have become complicated. However, this problem is avoided when the transformers are implemented in the visited MSC. In 3G, the same Adaptive Multi-Rate (AMR) codecs will be supported as in GSM. As a result, an operator can rely on the underlying GSM coverage and needs to build 3G coverage only when required.
2.1.0.1 NSN MGW for 3G-MSC To ensure a smooth evolutional path from GSM to UMTS, the interworking unit has been introduced.
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Figure 5 shows an NSN IPA 2800 NSN MGW architecture:
Fig. 5 NSN IPA 2800 NSN MGW Architecture
The NSN MGW belongs to the latest version of the IPA2800 product family and is based on platform utilizing ATM technology for switching and internal communication. The main features of the NSN MGW platform are distributed processing, modularity, good on-line operability, and low power consumption. The main function of the NSN MGW is to provide interworking between 3G-RAN and GSM MSC and to perform transcoding between the A-interface and Iu-interface. The key functions of NSN MGW are as follows:
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NSN Products
ATM to Time Division Multiplexing (TDM) conversion Iu-A' interface signaling conversion between narrowband and broadband SS7 Transcoding Figure 6 shows an MGW for 3G-MSC architecture:
Fig. 6 MGW for 3G-MSC Architecture zezenenu.und.lmm/xerojuko.en.slo
The main units of MGW for 3G MSC architecture are as follows: Control and Administrative Computer Unit (CACU ) controls the MGW for the switch fabrics of 3G-MSC and establishes connections for calls according to requests from the Signaling Computer Units (SCUs). Central Memory (CM) serves as a central data storage and distribution facility in the exchange. In addition, it handles the centralized part of the common channel signaling, for example, digit analysis. Interface Signaling Unit (ISU) is responsible for CN emulation and BSS signaling emulation towards the MSC. NEMU and its subunits compose a local user interface and interface towards the higher level NMS, perform O&M functionalities which are not handled by other computer units of the MGW for 3G-MSC, including post-processing of performance and fault management data, and provide Software upgrade support. Operation and Maintenance Unit (OMU) and its subunits. Signal Processing Management Unit (SPMU) controls the allocation of the MGW for the Digital signal processing DSP and CDSP computer resources of 3G-MSC. Configure digital signal processor, which in turn helps in load sharing, allocation of Transcoding Unit (TCU). ATM Switching Fabric Units (SFU) are used for switching the calls processed by the exchange.
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NSN Products
Multiplexer Units (MXU) are used for connecting the low-bit-rate network interface units, and the computer units and signal processing units, which have small to moderate bandwidth requirements, to the ATM switch fabric. AAL 2 Switching Units (A2SU) ensure efficient transport of information with limited transfer delay for low-to-moderate bit-rate units connected to the main switch fabric.
2.1.0.2
MSC Server System(MSS)
Exact specifications for the interfaces between the modules make it possible to add new functions without changing the system architecture and enable the system’s remaining up-to-date throughout its long operational life. The possibility to build different network elements, which provide different functionalities, is a good example of the versatility of the HW architecture.
MSC Server (MSS) The MSS is a compact standalone server product that offers processing power that is needed when one server controls several MGWs. Basically the MSS does not have Group Switch for switching 64 kbit/s TDM channels but an optional small GSW can be included in the configuration if required for TDM based SS7 signalling.
MSC Server (MSSu) Similar to the MSS, the MSSu is also a compact standalone server product that offers processing power that is needed when one server controls several MGWs. The MSSu will not be a new delivery but instead it will always be upgraded from the operator’s current MSCi. In essence, the MSSu is a pure standalone server that does not have any TDM interfaces.
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Introduction All MSC Server products are based on NSN DX 200 hardware, which uses Intel Pentium processors. The Integrated MSC Server is a feature in the MSCi. Thus the HW configuration is similar to the MSCi as well. This ensures an easy and cost-efficient upgrade for the existing MSCi elements to Integrated MSC Servers. The standalone MSC Server is based on the DX 200 Server Platform. DX 200 Server Platform is a new HW configuration optimised for call control. It is a pure server configuration that utilises double computer cartridges. This minimises the floor space requirement and maximises performance. However, all plug in units are the same as in the DX 200 MSCi, so it also offers full synergy with other DX 200 elements.
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Fig. 7 Block diagram of MSS and GCS
Gateway Control Server (GCS) Presented in Figure 7 above is the block diagram of the GCS. It shows the interfaces between the functional units and also the interfaces connecting the system to the environment. A more detailed description of the functionality each unit performs is given below in section Functional Units. Note that GCS does not have following units: Base Station Signalling Units (BSU) is not furnished because the GCS does not handle signalling or control traffic towards radio networks. These units are available in MSS. Visitor Location Register Units (VLRU) is not furnished in the GCS because subscriber information is handled in the visited MSS where these units are available.
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Integrated MSS As a regular MSC can be upgraded to the Integrated MSS it can be seen that block diagram of Integrated MSS includes all the functional units available also in a regular MSC. Naturally here the GSW is included since this network element can also handle user and control plane traffic on TDM lines. Integrated GCS The basic block diagram of the Integrated MSS also applies to the Integrated GCS with the following exceptions:
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Base Station Signalling Units (BSU) is not furnished because the Integrated GCS does not handle signalling or control traffic towards radio networks. Compact Data Service Units (CDSU) are not furnished because the Integrated GCS does not need analogue/digital modem pool as the CS Data Interworking Functionality is handled in the Integrated MSS or in a separate NSN Circuit Switched Data Server (CDS) network element. Visitor Location Register Units (VLRU) is not furnished in the Integrated GCS because the subscriber information is stored in the visited MSS or the MSC.
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Fig. 8 Block Diagram of Integrated MSS and Integrated GCS
2.1.0.3 NSN HLR In the NSN 3G solution, the same HLR is used for GSM, UMTS, and GSM/UMTS dual-mode users. With only some additional functionality added, the present HLRs will support new services in both UMTS and GSM. The benefit of the one-HLR solution is the ease of management that comes with a centralized subscriber database. When existing GSM users subscribe to a GSM/UMTS dual-mode service, operators only need to activate the service in the HLR database for the subscriber.
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The HLR provides database storage and manipulation of: Subscriber profile data Authentication data Equipment identity data specifying white, grey, or blacklisted mobile equipment identities
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The HLR contains static information, for example, subscriber identity, authentication and security data, semi-dynamic information, for example, the current subscriber profile with activated supplementary services. In addition, the HLR contains dynamic data, for example, mobility management data.
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Figure 9 shows a DX200 HLRi:
Fig. 9 DX200 HLRi
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2.1.0.4 Number Portability - Service Routing Register (SRRi) One of the problems that the operators face today is that many mobile users switch from one operator to another but do not want to change the number of their mobile phone. The problem is worse for operators in a 3G-environment. Now, the problem may be resolved as the telecom authorities in several countries have mandated the implementation of the Mobile Number Portability (MNP). In many European countries, the number belongs to an individual legally. When implementing MNP, it is difficult to maintain the services for the operators when the subscribers move from one network to another. It also affects the efficiency of the operators because it is difficult for the MSCs to track the HLRs needed to be queried in order to find the subscriber.
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Figure 10 shows the reason for the MNP:
Therefore, at present many networks use a solution to improve the storage of the subscriber information to reduce the load of updating the MSCs and excessive signaling. The NSN solution uses the features of MSC features and/or a network element known as the SRRi. The NSN DX200 i-series SRRi is a high-capacity network element that meets European Telecommunications Standards Institute (ETSI) specifications. ETSI specifications are now being formulated for the MNP as well. All subscribers are registered in the SRRi with the address of their HLR. As a result, the MSC only needs to check from the SRRi.
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Fig. 10 Reason for the MNP
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Figure 11 shows the MNP Architecture:
Fig. 11 MNP Architecture
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When a request from the MSC is received, the single number database is checked. If the number is not found from the single number DB, then the number range database is checked. This ensures that numbers can be inserted in a flexible manner; for example, single number can be part of some number range. The NSN SRRi supports 700,000 number ranges, and the single number database has 56 millions entries out of which 7 million entries are in minimum configuration. Expansion of the database is also possible. The SRRi can be equipped to support 1824 SS7 links and 192 PCM interfaces. In addition, it can manage 120,000 DB queries. The number of queries managed will increase in future. The SRRi also has different options for interfaces. The options are Mobile Application Part (MAP), Core Intelligent Network Application Part (INAP) and Simple Spectral Access Protocol (SSAP). In the future, it will have interfaces for other Intelligent Network (IN) protocols and IP-based protocols.
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Figure 12 shows the SRRi Architecture:
The main units of the SRRi are as follows: Central Memory and Marker (CMM) units Exchange Terminal(ET) CCS7 Signaling Units (CCSU ) Statistical Units (STU) Database Distributor Units (DBDU) sends subscriber related data to the correct SRRU pair. Clock System Unit (CLSU) Operation and Maintenance Unit (OMU) Group Switches (GSW) Service Routing Register Units (SRRU) is responsible for updating, removing and retrieval of subscriber data.
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Fig. 12 SRRi Architecture
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2.2
Packet Switched - PS Domain
Many of today's networks include architecture to support packet data transfer between the network and the subscribers. This type of bearer service is ideal for burst applications, such as Internet access or the WAP, messaging, and a range of content. The radio component of General Packet Radio Service (GPRS) is clearly defined and can be implemented on almost any network. The Iu and Gb-interfaces support the carrying of packet information between the GPRS core and the RNC and BSC, respectively. Figure 13 shows the architecture of the packet network:
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Fig. 13 Architecture of the Packet Network
2.3
GPRS Evolution For 3G
GPRS was built to be added to a GSM network. In UMTS, packet data is inherent within the specifications and many of the mobility functions that the 2G-SGSN performs in GSM are not needed for UMTS. Therefore, in the NSN solution, we need to use 3G SGSN which is based on different platform compared to 2G SGSN. All the other GPRS and backbone components can support UMTS with a software upgrade.
2.3.1
3G-SGSN
The basic functions of the 3G-SGSN are as follows: Authentication and mobility management. Routing of data to the relevant GGSN when a connection to an external network or intra-network mobile to mobile connections are required.
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Generation of charging data and traffic statistics. In the NSN solution, the 2G-SGSN is built on the DX200 platform, while the 3G-SGSN is built on the IP platform.
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Figure 14 shows the NSN 3G-SGSN:
Fig. 14 NSN 3G-SGSN
There are two main differences between the Gb and Iu interfaces. 1.
In UMTS, the role of RNC for the mobility management is more important than the role of BSC in GSM.
2.
The protocol used between the SGSN and BSC is based upon Frame Relay (FR), but the connection between the SGSN and RNC is based upon ATM.
For a customer with a current GPRS network, support for UMTS is received by adding the 3G-SGSN into the network and defining the interfaces to other elements such as the GGSN and HLR. The NSN 3G-SGSN has mainly two roles as follows: The control part of the 3G-SGSN consists of the mobility management layer, which handles the mobility and security, and the session management layer, which handles the Packet Data Protocol (PDP) context activation and QoS reservation. The 3G-SGSN also performs packet processing and routing.
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The NSN 3G-SGSN is a compact modular device based on a scalable NSN routing platform, which enables flexible configurations. The NSN 3G-SGSN consists of the hardware blocks managing the functions as follows: Tunneling IP forwarding SS7 interface Operation and Maintenance Mobility and session management Figure 15 shows an overview system structure of the 3G-SGSN:
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Fig. 15 System Structure of NSN 3G-SGSN
The architecture of the NSN 3G-SGSN is based on a modular multiprocessor architecture. The SGSN has a maximum of 16 high-performance computer units with local memory. The backplane switch and the system together provide redundancy and linear scalability for the NSN SGSN. The SGSN capacity may be optimized for maximum data throughput or for maximum number of simultaneous subscribers. The maximum capacity when optimized for maximum throughput is as follows: 300,000 subscribers 200,000 PDP contexts 900 Mbps throughput In order to reach the throughput of 900 Mbps, the number of PDP contexts should not be more than 200,000. The throughput decreases slightly as the number of PDP contexts grows. The maximum capacity when optimized for the maximum number of PDP contexts is:
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300,000 subscribers 600,000 PDP contexts 600 Mbps throughput The maximum number of PDP contexts 600,000 is the absolute maximum number of PDP contexts with which thefor achieving throughput of 600 Mbps is 600,000.
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Figure 16 shows the interfaces of NSN 3G-SGSN:
Fig. 16 Interfaces of NSN 3G-SGSN
The NSN 3G-SGSN has the following interfaces in the 3G network: The interface between a 3G-SGSN and a GGSN is the Gn. It uses the GPRS Tunneling Protocol (GTP) according to the ETSI0960 specification with QoS enhancement as according to the UMTS2307 specification. The Iu-interface connects the 3G-SGSN to the serving RNC. The Iu-interface is based on ATM technology and has separate user and signaling planes. The user plane uses IP over ATM technology, while the signaling plane uses broadband SS7. The Gr and the Gf are the interfaces to the HLR including the EIR and the AuC. Mobility management procedures use MAP interfaces between the 3G-SGSN and the HLR. The 3G-SGSN and the Charging Gateway (CG) use the Ga-interface and the standard charging protocol GTP, [GSM1215], while the interface to the NMS is used to send alarms to the network management.
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2.3.2
GGSN
The NSN GGSN acts as an interface between the GPRS network and external networks. For the external network, the GGSN is simply a router to a subnetwork. When the GGSN receives data addressed to a specific user, it checks if the address is active. If the address is active, the GGSN forwards the data to the SGSN that serves the mobile or else the data is discarded. In addition, the GGSN routes mobile-originated packets to the correct external network. The same GGSN can serve GPRS and 3G subscribers simultaneously.
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Figure 17 shows an NSN GGSN:
Fig. 17 The NSN GGSN
The GGSN Release 2 software will run on the IP650 and IP740 hardware platform. The capacity of the GGSN with Release 2 software as installed on the IP650 is as follows: 150,000 PDP contexts 100 Mbps throughput with 1400 byte packets 1000,000 PDP contexts 400 Mbps with 1400 byte packets. Border Gateway (BG) The NSN BG is a router that can provide a direct GPRS tunnel between different operators’ GPRS networks through an inter-Public Land Mobile Network (PLMN) data network and does not transfer data between operators through the public Internet.
2.3.3
Domain Name System
Domain Name System (DNS) is a server containing a directory of Internet names against the IP address of the server. The CN DNS is used to find the right GGSN corresponding to an Access Point Name (APN) provided during PDP context activation.
2.3.4
Charging Gateway (CG)
In the CS domain, charging is managed by the MSC and is based on the time of the connection. In the PS domain, it is not feasible to charge on time because a subscriber may have an active connection for an extended period, but without actually transferring data. Therefore, in the packet domain an independent server is used to identify the packets of data being transferred. By tracking each subscriber's usage a charging ticket is created and sent to the billing system of the operator.
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The new IP740 platform supplies the following:
NSN Products
2.3.5
Legal Interception Gateway (LIG)
A new network element is necessary to meet the requirements of regulators and governments concerning the legal interception of packet traffic. The NSN LIG acts as an interface between the CN and the network of the authorized security organization.
2.3.6
FlexiFamily
The first members of the FlexiFamily to be introduced are the open, carrier-grade NSN FlexiServer (TM) and NSN Flexi Gateway (TM) platforms. The NSN FlexiServer is a high-availability carrier-grade server platform, which uses the Linux® operating system. The use of mainstream hardware technologies and open-interface software components facilitate fast product creation. NSN IP Multimedia Core servers implementing 3rd Generation Partnership Project (3GPP) IP Multimedia Subsystem will be based on NSN FlexiServer. These network servers will eventually supersede current mobile switches, enabling mobile networks to provide rich-call capabilities far beyond present voice and messaging-centric services. For radio access, the NSN FlexiServer is used for products that manage the control plane for mobility and connection functions, including common radio resource management. zezenenu.und.lmm/xerojuko.en.slo
The NSN FlexiGateway is a carrier-grade gateway platform and the future basis for network user-plane functions, such as packet routing and processing. Based on the modular design of the embedded NSN FlexiServer and tightly integrated with a highly efficient fault-tolerant routing platform, the NSN FlexiGateway enables the independent scalability of packet routing and processing functions. NSN FlexiGateway, with specially designed content-aware provisioning extensions will be used to gradually complete the implementation of the All-IP architecture.
2.4
Flexi ISN 3.2
Introduction Flexi ISN Release 3.2 is a scalable carrier-grade product incorporating gateway GPRS support node (GGSN) and service awareness functionality. It acts as a gateway between wireless access networks and data networks like the operator’s service networks, a corporate network, or the Internet. With the tools supplied by Flexi ISN, operators can offer attractive services to targeted subscriber segments with flexible charging models.
2.4.1
Operating software functions
The Flexi ISN uses the NSN Networks IPSO operating system. The Flexi ISN Release 3.2 (FI 3.2) operating system version is IPSO 3.9.2NET. Flexi ISN is based on NSN IPSO operating system, running in FlexiServer Blade hardware. Flexi ISN inherits the wellproven Voyager user interface for managing IPSO
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operating system and the applications. Management is also possible with Centralised Network Services Manager (CNSM), which is a separate NSN product. Both Voyager and CNSM are accessible with Web browsers.
2.4.2
Basic application software
The fundamental tasks of the Flexi ISN are to offer gateway GPRS support node (GGSN), multiaccess support, and traffic analysis (TA) functionality. The Flexi ISN acts as a gateway between wireless data networks and external data networks such as the Internet. The Flexi ISN supports multiple deployment options on Gn and Gi access network connections. The basic application software of Flexi ISN software is available as two features: 'GGSN' and 'NAS'. For the Flexi ISN to function, at least one of these features, or both, are required.
Hardware
Flexi ISN utilises multi-CPU hardware to provide a high performance, scalable ISN solution. At the same time it uses built-in high availability mechanisms to provide mobile users with fault tolerant access to services. Redundancy is transparent to the other network elements because Flexi ISN hides its multi CPU structure, appearing as a single IP router and application platform. The logical structure of Flexi ISN is shown in Figure 18. Each processing unit is running its own instance of IPSO operating system. These units, Blades, are connected to each other via internal networks. These internal networks are called Backplane networks. To switch packets in the internal networks the system includes two built-in Layer 2 switches.
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2.4.3
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Fig. 18 Logical structure of Flexi ISN
Some of the Blades also have external network interfaces, which are used to integrate Flexi ISN to the GPRS/3G network, and for forwarding packets to and from the mobile users. The Blades have their specific roles in a functioning Flexi ISN system. In principle, all important functions can be handled by more than one Blade, and thus the system is very resilient to failures . The performance-intensive tasks are distributed to multiple Blades. Flexi ISN has excellent performance and capacity, since one system can have as much as 10 processing units.k
2.4.4
Session capacity
The Flexi ISN concurrent session capacity is sold in steps of 1000 concurrent PDP contexts. It is possible to order from 1 (1000 PDP contexts) up to 333 items (333 000 PDP contexts) in the entry configuration. Up to 666 items (666 000 PDP contexts) can be ordered in the medium configuration. Up to 1000 items (1 000 000 PDP contexts) can be ordered in the large configuration.
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Operator benefits The operator can scale the system capacity according to actual traffic needs.
2.5
IP Multimedia Subsystem
GPRS will continue to evolve. In addition, UMTS will also add capabilities to GSM/GPRS because the CN is shared with UMTS improvements. The IP Multimedia Subsystem (IMS) or IP Multimedia Core Network (IM-CN) will be a major change in future. The IP Multimedia CN subsystem contains a set of signaling and bearer related network elements for provisioning of multimedia services. IP multimedia services are based on an Internet Engineering Task Force (IETF) defined session control capability which, along with multimedia bearers, utilizes the IP-Connectivity Access Network The IP Multimedia CN subsystem enables PLMN operators to offer multimedia services based on and built upon Internet applications, services and protocols to their subscribers. The intention is that the multimedia services will be developed by PLMN operators and other third party suppliers including those in the Internet space using the mechanisms provided by the Internet and the IM CN subsystem. The IM CN subsystem will enable the convergence and access to voice, video, messaging, data, and web-based technologies for the wireless user and combine the growth of the Internet with the growth in mobile communications.
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Fig. 19 Mobile router functionality in the Flexi ISN enables forwarding of subnets behind the 3G/GPRS modem
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Figure 20 shows an example of IMS:
Fig. 20 Example of IMS
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The complete solution for the support of IP multimedia applications consists of terminals, IP-Connectivity Access Networks, and the specific functional elements of the IM CN subsystem. An example of IP-Connectivity Access Network is the GPRS CN with GSM EDGE Radio Access Network (GERAN) and/or UTRAN radio access networks. The actual IMS consist of a large number of functions enabling session control for IP connections. New elements in IMS CN are as follows: Connection Processing Server (CPS) for controlling multimedia sessions using Session Initiation Protocol (SIP) and for centralized registration and charging IP Multimedia Registers for storing subscriber and service information Further information on the IMS is available in: 3GPP TS 23.228 3GPP TS 22.228 www.NSN.com
2.6
Push-To-Talk Over Cellular (PoC) System Architecture
Push to talk one-to-one and group calls are enabled over GPRS and Enhanced General Packet Radio Service (EGPRS) networks. A User logon to the network means logon to the PoC service, which is a SIP registration. Group sessions are created with SIP messages between the PoC CN and terminals. To join a group
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call the user creates a SIP session. The SIP is only a signaling protocol. The actual voice is relayed by the user plane of the PoC Call Processor as Real-time Transport Protocol (RTP) packets. If group connections are required, they are created by multiplying voice packets to all members of a group session. Therefore, the PoC creates a radio group based on the end user choice of members.
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Figure 21 shows a PoC Architecture:
Fig. 21 PoC Architecture
In order to create a sufficient QoS in loaded networks, GPRS transmits the PoC voice using 3GPP release 99 streaming and header compression features and release 4 feature package 1. This is necessary to counter the unpredictable nature of the GRPS PS interface Two PDP contexts per PoC service logon must be created. One of the PDP contexts is a streaming context and is used for mainly the speech packets and some control packets, for example, for starting a one-to-one call session and talking party identification for group talkbursts. The other PSP context is a best effort context and is used for the SIP signaling and text chat within a talkgroup. The SIP signaling is used for service logon or logoff including authentication, joining or detaching a group session, and information request.
2.7
Intelligent Content Delivery
The NSN Intelligent Content Delivery (ICD) solution offers mobile terminal users with an easy access to all their services from a single access point. With the NSN ICD solution, operators can offer easily accessible content services with pricing that reflects the value of the services popular with subscribers. The ICD solution provides a rich set of service control functions that enhance the user experience
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and fulfill the ethical and regulatory requirements of mobile content delivery.
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Figure 22 shows the ICD components:
The ISN consist of GGSN and two data analyzers as follows: Traffic Analyzer (TA) - The TA handles HTTP traffic with high granularity. For example, decisions can be based on URL. All layers of the IP stack are visible to the TA. Content Analyzer (CA) - The CA operates only at layer 7. Therefore, it can recognize detailed information in the traffic flow, content type, and headers. One of the major functions of the NSN ICD is to bring intelligence to the packet CN. The ICD system is service aware. It classifies traffic by IP address, protocol, and destination URL, allowing traffic to be priced according to benefit from specific type of data to the user. The benefits of the ICD solution are as follows: Integrates subscription, customer care, and billing solutions into a seamless functionality Includes online charging data and online subscriber and services management throughout the network Provides simple and standard interfaces to operators' existing billing and customer care systems Minimizes the required integration work for new services due to the well-defined interfaces with external systems Provides a rich set of service control functions that improve the user experience and meet the ethical and regulatory requirements of mobile content delivery
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Fig. 22 The ICD Components
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Allows user access to multiple services through one single access point, making the use of data services considerably easier and attractive for the end users Charging options in ICD are more flexible than earlier charging because of the reasons as follows:
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Volume -based charging depending on: Transferred data volume Per service, not limited to PDP Context Bytes of transferred data Event-based charging depending on: Event, which means transaction or hit to a specific WAP/ Hypertext Transfer Protocol Uniform Resource Locator (HTTP URL) A request or response pair Number of events Time -based charging depending on: Distinguished active or inactive usage time Subscription or free access during subscription period Seconds of data transfer Subscription-based charging depending on: Free access during content service subscription period Whether Combined or not with event-based charging
2.8
NSN Intelligent Enhanced Data Rates for GSM Evolution
Intelligent Enhanced Data Rates for GSM Evolution (EDGE) is the new CN for IP services. It is based on the NSN end-to-end solution approach and is implemented using the existing packet core of the operator as foundation. The technology is called EDGE because most of the functions are implemented at the boundary of the access network where all IP traffic passes from different access networks, both wireless, and fixed. From EDGE, operators are able to control many operations, for example, the RAN resources, which account for 60-80% of costs. In addition, EDGE is where operators can enable multimedia communication convergence. The Intelligent EDGE is based on an open architecture that supports multi-vendor implementations and enables operators to exploit the widest possible mixture of different business models while building coherent, holistic networks.
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Figure 23 shows the NSN Intelligent EDGE:
The Intelligent EDGE implementation is based primarily on NSN ICD, Messaging of NSN, Presence and PoC solutions, and the NSN IMS.
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Fig. 23 NSN Intelligent EDGE
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3
NSN UTRAN Solution
3.1
Radio Network Controller (RNC)
3.1.1
INTRODUCTION to RAS6
RAS06 introduces HSUPA functionality and enhancements in HSPA functionality such as HSDPA capacity improvements to support dynamic resource allocation, code multiplexing, high data rates and cost-efficient HSPA transport solution functionality. In transport solutions, RAS06 brings several transport improvements, such as efficient usage of Iub bandwidth and Hybrid BTS backhaul to enable cost-efficient Iub traffic. In operability and performance solutions, many new features are introduced in RAS06 to improve system maintenance and troubleshooting.
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3.1.2
RNC450
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The NSN Radio Network Controller (RNC) is based on a fault-tolerant packet switching platform. The main function of the RNC is to control and manage the Radio Access Network (RAN) and the radio channels. The RNC is designed for efficient use of radio resources, and easy operation and maintenance.
Fig. 24 NSN radio network controller RNC450
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The RNC provides logical interfaces for the MSC, the MGW, other RNCs, the NSN NetAct, BTSs, the Serving GPRS Support Node (SGSN) and the Cell Broadcast Centre (CBC).
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The Radio Access Network (RAN) reference model defines a system consisting of the functional network elements, the RNC and the BTS. Each BTS is connected to only one RNC through Iub interface, whereas an RNC can be connected to a number of other RNCs through Iur interface. Each RNC is also connected to the MGW, MSC, 3G-CBC and 3G SGSN through Iu interface. The RNC supports a connection to multiple core networks. The multi-operator RAN feature enables sharing of the RAN, including the RNC, between several operators.
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Iub interface (RNC-BTS) The Iub interface telecommunication part takes place between the RNC and the BTS. To be fully compatible with the 3GPP Iub interface, the Layer 3 Control Plane Protocol (NBAP protocol) is implemented according to the 3GPP TS25.433: UTRAN Iub interface Node B Application Part (NBAP) signalling instead of the NSN NBAP specification. The main differences between NSN and 3GPP protocols are in the Logical O&M part of the NBAP. Also, some other NBAP procedures of RAN release 1 require changes to be fully compliant with the 3GPP NBAP specification.
Iu interface (RNC-MSC and RNC-SGSN) The Iu interface between the core network and the RNC is divided into two separate functional parts to support circuit-switched and packet-switched services to the core network. The Iu interface is implemented according to the 3GPP standards. The open Iu interface means that the RNC can be connected to the core networks of other suppliers. Iu-BC interface (RNC-CBC) The Iu-BC interface between the MSC and the CBC is implemented according to the 3GPP standards. The open Iu-BC interface means that the RNC can be connected to the CBC (part of core network) of other suppliers. Iu-PC interface (RNC-SAS) The Iu-PC interface is a logical interface for the interconnection of the Stand-Alone SMLC (SAS) and the RNC through the PCAP protocol. The SAS provides GPS assistance data to the RNC and may perform the position calculation function for various positioning methods.
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Iur interface (RNC-RNC) The Iur interface is used to support soft handovers within the RAN. Connections that are managed by two RNCs are managed by soft handovers. All necessary data from the Serving RNC (SRNC) is transferred to the Drifting RNC (DRNC) across the Iur interface. The Iur is an open and standardised interface.
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3.1.3
Network management interface (RNC-NetAct)
The Data Communications Network (DCN) architecture provides connections for the implementation of O&M functions from the radio access network to the operation support system (the NetAct). A common transport protocol is provided for the DCN network and the IP is used as a flexible solution for network management. Network management operations are initiated from the NetAct, messages related to these operations are routed by the RNC to the appropriate network element. The DCN to realise this is based on TCP/IP communication protocol. RNC and NetAct application level communication is based on CORBA, while communication between RNCs and BTSs takes place across the Iub interface. The RNC provides the LAN interface (Ethernet) or IP over ATM (IPoA) connection to the rest of the O&M network. IPoA and LAN connections can be combined to achieve redundant O&M connections to the RNC from the NetAct. The MML command line interface is available through telnet.
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3.1.4
RNC450 architecture
The RNC has a modular software (SW) and hardware (HW) structure, which allows scalability of processing power and switching capacity, as well as flexibility in terms of the number and types of interfaces. Because of exact specifications for the interfaces between different modules, extra functions can easily be added without changing the architecture of the system. Therefore, the RNC has a long operational life span and can still contain additional up-to-date features. For more information on the existing RNC features, see the feature documentation for the previous releases. For more information on additional features, see RAS06 documentation for radio resource management and telecom features. The complexity of services envisioned for future networks calls for computing power in the network elements. The RNC is well-positioned to provide the required scalability and flexibility through the distributed, fault-tolerant computing environment provided by the fault-tolerant computing platform.
A hardware platform based on standard mechanics provides cost-efficiency through the use of modular, optimised and standardised solutions that are largely based on commercially available chipsets. In Figure 26, a block diagram of the RNC shows the general functional architecture of the RNC. At high level, the network element consists of the following parts: network interface functions switching and multiplexing functions control plane functions user plane functions O&M functions
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The packet switching platform provides generic ATM functionality, common for several application areas, such as statistics, connection control, traffic management, operations and maintenance, and resource management.
NSN Products
The functions are distributed to a set of functional units capable of accomplishing a special purpose. These are entities of hardware and software. The main functional units of the RNC are listed below:
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The control computers (ICSU, RRMU and RSMU) consist of common hardware and system software supplemented with function-specific software. The AAL2 switching units (A2SU) perform AAL2 mini packet switching. The Data and Macro Diversity Unit (DMCU) performs RNC-related user and control plane L1 and L2 functions. The Operation and Maintenance Unit (OMU) performs basic system maintenance functions. The O&M Server (OMS) is responsible for RNC element management tasks. The OMS has hard disk units for program code and data. The Magneto-Optical Disk Drive (FDU) is used for loading software locally to the RNC. The Winchester Disk Unit (WDU) serves as a non-volatile memory for program code and data for the OMU. The Timing and Hardware Management Bus Unit (TBU) takes care of timing, synchronisation and system maintenance functions. The Network Interface Unit (NIU) STM-1/OC-3 (NIS1/NIS1P) provides STM-1 external interfaces and the means to execute physical layer and ATM layer functionality. The NIU PDH (NIP1) provides 2 Mbit/s / 1,5 Mbit/s (E1/T1) PDH external interfaces and the means to execute physical layer and ATM layer functionality. The GPRS Tunnelling Protocol Unit (GTPU) performs RNC-related Iu user plane functions towards the SGSN. The External Hardware Alarm Unit (EHU) receives external alarms and sends indications of them as messages to the OMU-located external alarm handler through HMS. Its second function is to drive the Lamp Panel (EXAU), the cabinet-integrated lamp and other possible external equipment. The Multiplexer Unit (MXU) and the Switching Fabric Unit (SFU) are required for switching both circuit- and packet-switched data channels, for connecting signalling channels and for the system's internal communication.
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Fig. 26 Block diagram of the RNC
Major Upgrade from RNC196 to RNC450 For RN3.0, NEMU has been replaced by OMS and MCPC2, MCPC2-A, HDS9, and HDS are no longer supported CCPC2-A for OMU, MDS/MDS-B for FDU and HDS9/HDS for WDU are no longer supported CCPC2-A and CDSP-B are no longer supported. Thus, plug-in unit upgrades from CCPC2-A and CDSP-B are no longer needed during the upgrade as the units need to have been upgraded already before the RN3.0 SW release upgrade. Not supported in RN3.0 Upgraded to
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MCPC2, MCPC2-A
MCP18-B
HDS9, HDS
HDS-A
CCPC2-A
CCP18-C / CCP18-A
MDS, MDS-B
MDS-A
CDSP-B
CDSP-C
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NSN Products
Table 1 Major Upgrade from RNC196 to RNC450
Fig. 27 Capacity Steps in RAS05.1 (RNC 196)
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3.2
NSN Base Station Solutions
To support the high penetration levels of subscribers and the new services and applications, a range of base stations with different sizes and capacity are required to support the varied environments that are used in GERAN or UTRAN. When building and developing a network, one key aspect to take into account is the complexity of the transmission network. In an operating UMTS network, there are different transmission solutions between different elements for carrying signaling and user traffic. Figure 28 shows the NSN WCDMA base station solution:
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The NSN solution consists of different Node B models that are used in different geographical locations to meet the local needs. These models are called the NSN UltraSite and MetroSite BTS. The models were supporting GSM and EDGE Transceivers (TRXs) and now they support WCDMA carriers. In addition, both solutions allow existing transmission networks to be used for UMTS traffic. As part of the planning process, the best suitable base station should be used, depending on the estimated capacity required in an area, the type of environment, which means the outdoors or indoors, location of environment, for example, road side, cost because it is cheaper to co-locate UMTS and GSM together, and many other factors. You will first learn some basic concepts and then about the different NSN UMTS base stations.
3.2.1
How to Read n+n+n Notation
In this chapter, you will see the notation of a 1+1+1 or a 2+2+2 site. This means that the transceivers or carriers in a site are divided into different cell directions. In addition, different antennas are used in different directions and the RNCs handle each cell independently. The actual number, for example, 2, represents the amount of carriers or TRXs covering certain specific cell areas. There is a big difference between the WCDMA and the GSM. In the Frequency Division Multiple Access - Time Division Multiple Access (FDMA-TDMA) system GSM, TRXs in specific areas are on a different frequency to avoid interference between the carriers. In WCDMA, the frequency is the same for carriers or TRXs in different cells. Therefore, in a 2+2+2 site, there are only two carrier frequencies used because a WCDMA carrier has more capacity and bandwidth than an equivalent GSM TRX. In
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Fig. 28 NSN WCDMA Base Station Solution
NSN Products
addition, the number of frequencies per operator is limited. Usually, 2 or 3 WCDMA carriers are licensed to one particular operator. Figure 29 shows the cell and TRX and carrier relationship:
Fig. 29 Cell and TRX and Carrier Relationship zezenenu.und.lmm/xerojuko.en.slo
Finally, there are different types of antennas used with different sizes and shapes. The choice of an antenna depends on the desired characteristic needed in a cell. For example, for coverage along a main road in a scarcely populated area, a directional antenna with well-defined beams can be used to focus the energy onto the road.
3.2.2
Legacy Base Stations
Currently, an existing GSM operator normally has a substantial countrywide coverage because GSM base stations have now been available since 1991. At NSN, different types of base stations have been introduced in the past 10 years. These base stations have gradually become smaller, offering more capacity and better quality. NSN has supplied GSM networks with a range of base stations, for example, the Talk Family BTSs. With the implementation of UMTS networks, the base stations will still be used for GSM traffic. Therefore, the aim of the network planning is to use these existing sites and re-use equipment where possible. The new NSN base stations are designed with the intention that they can be co-located with the older models.
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NSN Products
Figure 30 shows an UltraSite base station co-located with GSM Talk-Family:
When co-locating a site, (GSM and UMTS), another problem for a network planner is the antenna arrays. The sight of a mobile antenna array is socially unacceptable, therefore, clever solutions are used to reduce the ugly and excessive look of the antenna. In Figure 30, the co-located, Talk-Family and UltraSite, BTS is situated on a roof and connected to the BSC through another BTS or other equipment through the use of a radio relay.
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Fig. 30 UltraSite Base Station Co-Located with GSM Talk-Family
NSN Products
3.2.3
NSN GSM/EDGE/WCDMA UltraSite BTS
NSN UltraSite BTS Indoor and Outdoor for GSM are offered as 1 to 12 TRX cabinets. Alternatively, they can be configured to hold up to 6 TRXs and an optional integrated battery back-up system. Up to 40 Ah capacity can be provided, which means 45 minutes of back up time for those 6 TRXs. NSN UltraSite BTS Midi Indoor, a 1 to 6 TRX BTS for indoor installations, is also available. The NSN UltraSite BTS can support GSM EDGE TRX with minimum hardware changes. Only the is changed while the other units remain the same. GSM and EDGE TRX can co-exist in the same cabinet with EDGE TRXs occupying the lower half of the UltraSite cabinet. WCDMA carriers can also be added into NSN UltraSite BTSs. They can operate simultaneously with the basic GSM and EDGE TRXs. The use of WCDMA equipment reduces the maximum number of basic GSM and EDGE TRXs to six in one cabinet. The UMTS configuration can be either three WCDMA carriers each with output power of 5W or 6 WCDMA carriers each providing 2 W output power. zezenenu.und.lmm/xerojuko.en.slo
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Fig. 31 NSN UltraSite Cabinet
This makes the NSN UltraSite BTS an efficient solution for building capacity in mobile networks in the places that require heavy telecommunication traffic. With the BTS high output power and receiver sensitivity of the BTS, large coverage can be achieved in rural areas when building the network. The output power can be further increased with an optional booster. Chaining the NSN UltraSite BTSs can increase the capacity. In most configurations, only the synchronization cabling is required between the cabinets. Up to 9 NSN UltraSite BTSs can be chained together. With Radio Frequency (RF) hopping, sectors split between different cabinets can use common hopping frequencies. BaseBand frequency hopping is not possible between the chained cabinets. The cabinets must have separate hopping groups. However, BaseBand hopping with TRXs in a single-cabinet sector is supported.
3.2.4
NSN WCDMA UltraSite Solution
The GSM EDGE UltraSite BTS has the capability to support WCDMA carriers. In addition, NSN provides a family of dedicated WCDMA base stations. There are basically three versions available in both indoor and outdoor configurations.
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Figure 31 shows the NSN UltraSite Cabinet:
NSN Products
Figure 32 shows the NSN dedicated WCDMA UltraSite BTS solution:
Fig. 32 NSN Dedicated WCDMA UltraSite BTS Solution
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The UltraSite Supreme has the capability to support 12 WCDMA carriers evenly in a maximum of 6 sectors. The UltraSite Optima has a maximum of 6 WCDMA carriers and is ideally suited when the space available is minimum.The final member is an extension to the Optima called the UltraSite Optima Compact, which has the same configuration as the Optima, but is integrated with a site support unit in the same cabinet. At a site, there may be different base station types and configurations to support the surrounding environment. When possible, the base station should share the same transmission lines to reduce cost and the same antenna arrays should be utilized to reduce the visual effect. In addition, a site support cabinet can be co-located at a site. This may include 3rd party transmission equipment, and battery back-ups. The Figure 33 shows a site with the site support. The NSN UltraSite uses a graphical tool to manage the site that can be operated either locally or remotely.
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NSN Products
Figure 33 shows the Site Support:
3.2.5
NSN MetroSite BTS
There are two different types of NSN MetroSite, a version that is used today in GSM and another version that will be introduced for UMTS. The MetroSite is a base station of an unobtrusive design, which is easy to install and is ideal for fast network rollout in diverse environments, such as roof, tunnel, small space, pole or wall. It supports complete triple-mode site solutions for high-capacity mobile multimedia for GSM, EDGE, and UMTS. MetroSite is Ideal for micro-cellular networks, in-fill applications and roadside coverage. It offers a good solution for quick and easy indoor coverage and is part of a wider integrated transmission solution. The MetroSite BTS can be attached onto a pole or wall, and is connected through to the BSC or RNC, through an integrated transmission solution of intelligent HUBs and Hoppers or Radios. In Figure 34, the WCDMA MetroSite is co-located on the same wall as a GSM MetroSite. However, both base stations use the same transmission equipment.
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Fig. 33 Site Support
NSN Products
Fig. 34 MetroSite Co-Located on the same wall as a GSM MetroSite zezenenu.und.lmm/xerojuko.en.slo
The coverage and capacity depends on the environment and parameters that have been defined by the network planning. The MetroSite solution is a set of products that are designed to work together as follows: The MetroSite BTS, which include GSM 900/1800, EDGE, and WCDMA. The BTS contains the TRX/Carriers that are used in the air interface. The MetroHub is a point in the transmission link, to which several sites will be physically connected through cable, microwave, or other connections with a link to the BSC or RNC. The Hub handles rerouting traffic in case of transmission link problems. The MetroSite Battery Back-up unit is a separate unit that is co-located with the BTS, which supplies temporary power to the BTS, in the case the main power supply fails. The MetroHopper radio is used for short microwave radio links between the BTS and BTS and/or HUB. The radios require a frequency of 58 GHz to work, which makes it ideal for transmission solutions in high-density areas, such as cities. The FlexiHopper radio is used when transmission is required for longer distances compared to when MetroHopper is used and can carry several links. It is ideal for connection to remote locations. Figure 35 shows the elements of the NSN MetroSite solution:
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NSN Products
In UMTS, capacity and coverage are closely related. The higher the capacity needed, the smaller the coverage area. Therefore, cheaper, smaller, easy to rollout, and maintainable sites are required. In the MetroSite solution, operators can use their existing transmission investments. Easy to use tools and features, such as auto-configuration of transmission equipment, can reduce rollout time.
3.2.6
3G FLEXI BTS
NSN Flexi WCDMA BTS is a part of NSN 3G macro BTS site solution. From a BTS site installation and hardware point of view, NSN Flexi WCDMA BTS introduces a new way to build BTS sites using modules, without a specific BTS cabinet. Due to its small weight and size, modular design and full frontal accessibility, NSN Flexi WCDMA BTS is easy to install in various locations. From a feature and performance point-of-view, NSN Flexi WCDMA BTS provides a smooth evolution from UltraSite WCDMA BTSs, without compromising performance or capacity. NSN Flexi WCDMA BTS modules can be used with different BTS configurations for an integrated site solution. The existing site support and auxiliary cabinets can be used to house NSN Flexi WCDMA BTS modules, or modules can be installed for example on a wall. NSN Flexi WCDMA BTS consists of two types of RF Modules per frequency band, one System Module, and a transmission sub-module. The same modules are used in both indoor and outdoor sites.
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Fig. 35 The Elements of the NSN MetroSite Solution
NSN Products
NSN Flexi WCDMA BTS is designed for easy installation, commissioning, and maintenance. One person can carry the modules and install them on the floor or on the wall. Due to the modular solution, the floor print, space, weight and power feeding system of the site can be optimised. The acquisition time, cost, and acceptance time of a new site is reduced.
3.2.6.1
Features of 3G Flexi BTS
Cost-efficient modular site With NSN Flexi WCDMA BTS, the same equipment can be used to build coverage and capacity. A high WCDMA carrier-capacity and wide coverage per site means fewer sites, which makes building a WCDMA network more cost-effective. NSN Flexi WCDMA BTS can be installed in an existing NSN Talk-family and UltraSite GSM/EDGE/WCDMA sites for a data capability upgrade; NSN Flexi WCDMA BTS is designed to use most of existing site equipment.
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Easy commissioning The auto detection feature of NSN Flexi WCDMA BTS makes commissioning and integrating fast and easy. The commissioning wizard guides the user step-by-step through the whole commissioning process. At the end of the process, the commissioning wizard produces a BTS Commissioning Report. Intelligent shut-down NSN Flexi WCDMA BTS with battery backup system supports an intelligent BTS site power shutdown procedure in case of an AC power failure. During the commissioning of each site, the operator can define different shutdown timers and priorities for the BTS sectors and carriers. For example, a three-sector two-carrier NSN Flexi WCDMA BTS (2+2+2) site equipped with battery backup operates as a transmission hub node towards other BTSs in a chain. The first timer can be set to shut down the second carriers of the BTS, to operate as 1+1+1 (for example) 30 minutes after an AC power failure. The second timer can be set to shut down the remaining 1+1+1 BTS one hour after the AC power failure. The timers can be set according to the configuration and priorities of each site.
Reliable operation Simplicity and speed of maintenance procedures improve operation reliability. Maintenance is improved by module integration and automatic fault detection procedures. Special attention has been paid to NSN Flexi WCDMA BTS SW start time, reducing, for instance, the downtime when a new SW package is taken into use.
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NSN Products
3.2.6.2
One BTS for all WCDMA network applications
Flexi WCDMA BTS is optimised for high-capacity and wide-coverage applications. It ensures cell ranges that meet the requirements of the coverage applications. Therefore, the number of sites required for building a WCDMA coverage is small. A seamless voice and data coverage area can be built easily. Flexi WCDMA BTS has been developed for coverage applications. It offers: high downlink power with Flexi 100 W Dual RF Module, optimum uplink performance and receiver sensitivity, outdoor modules that can be located close to antennas, reducing antenna feeder losses, optimised antenna system performance, including 3GPP antenna tilting and Mast Head Amplifier (MHA) support.
Flexi WCDMA BTS Optimised Antenna line includes the following optional features, enabled by SW Licence keys: Integrated MHA power feeding and O&M control to the RF Module of the Flexi BTS Antenna line supervision by Return Loss measurement Integrated 3GPP standard Antenna Tilt power feeding and 3GPP Antenna Tilt O&M control to the RF Module of the Flexi BTS Flexi RF Module has an integrated lightning protection circuit in all antenna connectors. The antenna connector of Flexi WCDMA BTS is on the RF Module front panel. No additional units, connectors, or jumper cables are necessary between the Flexi WCDMA BTS antenna connector and the antenna. This minimises the antenna line length and losses and optimises RF performance in both the uplink and downlink direction.
High-capacity HSDPA and HSUPA BTS Flexi WCDMA BTS is a compact high-capacity voice and data BTS designed to support future High Speed Downlink Packet Access (HSDPA) based services and High Speed Uplink Packet Access (HSUPA) based services.
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Antenna Line Optimised Antenna line is a separate optional site solution to further improve total BTS and antenna system site RF performance and to minimise costs.
NSN Products
Smooth HSDPA and HSUPA support is provided through SW. RF and System Modules simultaneously support existing voice, circuit, and packet data services. They also support HSDPA and HSUPA, meaning that no special HSDPA modules are necessary. The System Module can be used for high bit rates supported by NSN RAS HSDPA software. The processing capacity of the Flexi WCDMA BTS can be configured to support the maximum capacity that the WCDMA air interface allows. In addition to flexible traffic capacity, Flexi WCDMA BTS also allows a free mix of traffic patterns to accommodate whatever proportion of voice and data is required.
Channel capacity of FLEXI BTS Flexi System Module channel capacity is designed to support flexible and cost-optimised site capacity evolution. Standard Operating SW will include support for 32 Channel Elements (CE). The channel capacity of NSN Flexi WCDMA BTS can be optimised depending on the BTS configuration and the required traffic capacity of the BTS site. More TM channel capacity will be allocated remotely from NetAct by sending Channel Capacity SW Licence to Flexi WCDMA BTS. zezenenu.und.lmm/xerojuko.en.slo
The minimum number of Channel Elements allocated by SW Licence is one (1) CE supporting both uplink and downlink. Therefore, Flexi WCDMA BTS site capacity can be optimised in the step of one CE without a site visit.
3.2.6.3
GSM/EDGE and WCDMA co-siting
NSN has designed the NSN Flexi WCDMA BTS so that it is compatible with existing NSN BTS's and it is easy to install on an existing site.
Mechanics NSN Flexi WCDMA BTS modules have much smaller space requirements than those of NSN Talk-family and NSN UltraSite EDGE/WCDMA BTSs. Floor installations of modules can be done at the same fixing points. Power system When NSN Flexi WCDMA BTS is installed to an existing GSM/EDGE BTS site, the same connection types and power supply types can be used. The existing alarm connections, for example, the fire alarm and door alarm, can also be connected to NSN Flexi WCDMA BTS. Antennas To minimise the work in adding WCDMA antennas to GSM BTS sites, part of the existing antenna infrastructure can be reused.
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NSN Products
A diplexer is an attractive way to add the NSN Flexi WCDMA BTS to the existing site, if the additional loss can be tolerated in the antenna line. Actual losses depend on the combination but (for example) in the case of GSM 900/WCDMA, the typical loss is less than 0.5 dB. NSN supplies diplexers for all necessary combinations. The Multi Radio Combiner (MRC) solution makes it possible to build an antenna line sharing site with a minimum effect on existing system performance. Downlink causes only a slight degradation for the BTS performance. A typical downlink loss is less than 0.6 dB. The Mast Head Amplifier (MHA) will retain the uplink performance. There are three different MRC units that cover the bands: 850 MHz, 900 MHz and 2100 MHz. The MRC 850 and MRC 900 units give the possibility to co-siting GSM EDGE and WCDMA BTSs in the same frequency band through antenna line sharing. There are no limitations to system frequency allocation (G-G-W, G-W-G, W-G-G). The MRC 2100 unit allows WCDMA and WCDMA BTSs co-siting in the same frequency band through antenna line sharing. Using MRC units make it also possible to co-site third party BTSs.
Flexi WCDMA BTS Feederless and Distributed Site concept
Flexi WCDMA BTS Feederless and Distributed Site Solutions refer to a situation where the System Module and RF Modules or Remote Radio Heads are installed apart from each other. The benefits of the Feederless and Distributed Site Solutions compared to a traditional BTS site are listed below: Overall site RF performance is better compared to traditional installation. Uplink and downlink performances are 2…5 dB better compared with typical 30…80 meter long antenna feeders. The solutions open easier, new and optimized installation possibilities especially with difficult places. There is no need for mast head amplifiers. Flexi WCDMA BTS Feederless and Distributed Site solutions utilise various power distribution solutions. DC feed to the feederless or distributed site is provided either by a Nokia Siemens Networks power system or 3rd party products. The input for the System Module is floating 48 VDC. There are four basic power supply alternatives for the BTS site and its modules: Flexi Power Module (FPMA) or MIBBU concept with a site support module, batteries, and cabinet FPMA installed in the proximity of the RF Module FPAB for a single RF Module Flexi Rectifier Module (FRMx) 3rd party AC/DC system (must meet the ETSI 300 132-2 standard)
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3.2.6.4
NSN Products
3.2.6.5
Overview of Flexi WCDMA BTS transmission
Flexi WCDMA BTS System Module contains a transmission sub-module that provides the physical Iub interface to the radio network controller (RNC) or I-HSPA Adapter. The System Module can be configured with different variants: PDH (copper), microwave radios (Flexbus), and SDH (fibre optics). All transmission sub-module alternatives provide interfaces of a kind, for example, 4-8xE1/T1/JT1 or STM-1. In addition, a hybrid PDH/Ethernet sub-module is available, enabling to either backhaul all traffic over PDH or Ethernet, or to split traffic to parallel paths. All transmission sub-modules can be software-upgraded to support IP transport (IP based Iub). Migrating Flexi WCDMA BTS from an ATM-based 3GPP R99/R4 to IP-based 3GPP R5 architecture does not require any hardware to be changed and can be executed remotely. zezenenu.und.lmm/xerojuko.en.slo
3.3
NSN Site Solutions and Transmission
As mobile networks develop and expand, and additional capacity is required, more complex transmission solutions are needed to ensure reliability, efficiency, and reduced costs. For a GSM operator, the existing transmission network can be used in UMTS. A base station, such as UltraSite, supports both GSM and WCDMA. In other cases, Node B can be co-located with GSM and the same transmission lines can be used. Figure 36 shows transmission when both the RNC and BSC can be connected into HUB:
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NSN Products
The actual transmission lines can be optical, for example, between RNC and MSC. In the radio network, the transmission lines can be cable or microwave links. The selection of transmission line depends on the capacity of the site, the cost of the link, the environment, and the planning permission. There is no single site solution that will suits all. Instead, the selection of site solution is dependent on the environment. Some examples for environment that can influence the site solution are as follows: Rural or countryside Sub-rural or town Urban or city Road or highway Fill-in, city centre, or indoor A site may comprise a base station, external antennas, depending on transmission external radios, and possibly a site support unit. The additional unit may contain batteries that are used to keep the site alive during power loss. A rural site can serve a large area and is notable for tall masts with antennas on the top. In many cases, rural sites are connected in chains or loops to other sites. An urban site may be located on top of a building. These sites usually have large capacity and serve a limit area. Figure 37 shows an urban rooftop site:
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Fig. 36 Transmission methods
NSN Products
Fig. 37 Urban Rooftop Site with Directional Antennas
In urban areas, a base station may be concealed within a building with only the external antennas visible. zezenenu.und.lmm/xerojuko.en.slo
As more capacity is needed in urban areas, smaller flexible sites are needed to fill in the gaps and offer better coverage. The site may be part of a more complex transmission network, such as a network with loop or star configuration. The coverage of the cell is likely to be more specific than a larger rooftop site. Due to the size and flexibility of urban sites, they can be used for indoor solutions. When discussing sites, it is important to remember that it is not the size or type of base station that dictates the cell, but the parameters used. The limit in the base station is power; sensitivity and coverage, the behavior and characteristics of a site are dependent on parameters. When building coverage, the emphasis is first on the city and then the country, following the road or rail infrastructure. To support coverage through long stretches, sites are positioned along the route. Directional antennas may be used to focus the radiating beam in a certain direction. In many cases, road sites are in loop or chain configurations.
3.3.1
ATM and Physical Interfaces
ATM is selected as the transmission technology for the lower layers of the interfaces in UMTS. The principles behind ATM is to divide the information into small fixed sized cells and reduce the overhead as much as possible, for example, error detection of data. Due to the small fixed sized cells, the ATM can be efficiently implemented in hardware to increase the transmission speed and be efficiently used for variable bit rates.
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NSN Products
Network interfaces provide external interfaces and the means to execute physical layer and ATM layer functions, such as statistics, O&M, buffer management, and scheduling. Network interfaces map the ATM cells to the transmission frame structure of Synchronous Digital Hierarchy (SDH) or Plesiochronous Digital Hierarchy (PDH). A network interface unit may include one or more physical interfaces depending on the type of interface. Any interface can be configured as an Iu, Iub, or Iur interface for use.
STM-1 - This ATM network interface unit contains four SDH STM-1 optical interfaces providing an aggregate interface capacity of 622 Mbps. E1 - This ATM network interface unit contains 16 PDH E1 interfaces with Inverse Multiplexing for ATM (IMA) function, which allows flexible grouping of physical links to logical IMA groups. T1 - This ATM network interface unit contains 16 PDH T1 interfaces with IMA function, which allows flexible grouping of physical links to logical IMA groups. JT1 - This ATM network interface unit contains 16 PDH JT1 interfaces with IMA function, which allows flexible grouping of physical links to logical IMA groups. JT2 - This ATM network interface unit contains 8 PDH JT2 interfaces with IMA function, which allows flexible grouping of physical links to logical IMA groups. Ethernet - Local Area Network interface or Ethernet) is provided in selected Control Computer Units, for example, in OMU or through specialized Ethernet Hub (EHB).
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In addition to the network interfaces, synchronization interfaces and LAN interfaces are provided as follows:
NSN Products
4
UMTS Network Management Solutions
To reduce operational costs and to ensure quality in a growing, complex mobile network, an Operational Support System (OSS) is required. Figure 38 shows how the number of network elements has increased in the past 10 years:
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Fig. 38 Explosion of Network Elements
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Unlike in GSM, 3GPP has specified the behavior of the OSS system and the standards, which include the process on how to manage a network. This is known as Telecommunication Operations Map (TOM). The network management can be described as a system with different management levels involved in managing any system. The lowest layer is called the network element management handles the actual management of the network element, such as checking a unit, for example, Man Machine Language (MML). The next level is called network management, which handles the network-wide issues, for example, alarm monitoring or network integration. On top of network management, Service Management layer, which handles the functions that control the services offered by the network, such as coverage and capacity. Then, the Business Management layer on top, which consists of the systems that actually run the business, such as billing and administration systems.
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Unlike in GSM, the 3GPP specifications have focused on the higher layers to ensure better communication between vendors.
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Figure 39 shows the Telecommunication Management Network (TMN):
Fig. 39 The TMN
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The NSN solution for supporting the functions of each of the layers is known as the NSN NetAct Framework.
4.1
NSN NetAct Solution
The NSN solution to support the operation of a network is known as the NSN NetAct. The structure of the solution is not built round the technology but the functions and processes that an operator must perform to ensure the operation of the business. NSN has launched NSN NetAct Framework in order to support the transition from 2G to 3G. It also extends the multivendor integration capability of the NMS. NetAct provides a full-scale management capability for both packet data and traditional voice traffic, independent of technology. As a result, it is possible to deploy new technologies with the same system that manages the current infrastructure.
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Figure 40 shows the different functions that the NetAct supports. All the functions are brought together in a common framework and are connected to the physical network elements through a Unified Mediation and Adaptation (UMA) object, which allows NetAct to talk to NSN elements and 3rd party systems.
The NSN network elements, for example, RNC, Add Cross-Connect Card (AXC), BTS, provide the necessary functions on commissioning, setting up, or troubleshooting the individual equipment. NSN NMS, located on top of the managed network elements, provides tools for making large-scale modifications at the network level. Figure 41 shows how the TMN is visualized in the NSN 3G/UMTS solution:
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Fig. 40 NSN NetAct Framework
NSN Products
Fig. 41 TMN is Visualized in the NSN 3G/UMTS Solution
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4.2
NSN Element Management Tools
Element level management is handled by individual element managers, which can be operated remotely from the NMS or by local terminals. All NSN RAN elements handle the management function of monitoring and managing the element in question. The operator can access these management functions through a graphical user interface. The element management tools used are as follows: The NSN DX and IPA2800 based elements use the NEMU, which provides the operator with an easy access to the most recently used operations and maintenance activities. In addition, traditional MML access is provided for less frequently used functions. The NSN base stations include Web Access Management (WAM) units, which handle the BTS related O&M functions and carrier control. These management functions are available to the operator both centrally via the NSN NMS or RNC and locally through the WCDMA BTS manager or the BTS Local Management Tool. The NSN AXC or the ATM Cross Connect unit, which is integrated into the BTS, also has an element manager to enable the operator to monitor and configure the ATM transmission, cross-connections, and settings. Usually, the element managers are used locally for commissioning or setting up the equipment at the site. However, they are also centrally available in the NSN NMS for remote operations, for example, when configuring and troubleshooting a single network element. Figure 42 shows the NSN element tools that can be operated remotely:
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Fig. 42 NSN Element Tools Operated Remotely
4.3
NSN Network Management Functions
In this section, you will look at some examples of basic network management. Note that there many other processes outside the scope of this material.
4.3.1
NSN Network Monitoring Solution
The Network Monitor collects and stores real-time information from the network to detect faults in network elements and to monitor the quality of service provided by the network. It provides visibility to the network status in real-time – anytime, anywhere. The network monitoring functionality is generic across all network technologies. The alarms and performance data are handled in the same way regardless of where they originate from. Figure 43 shows the monitoring cycle of alarm, The alarms are detected, identified, handled, solved, verified, and then closed. The information for monitoring comes from different sources.
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The element managers are accessible through web. Therefore, the BTS and AXC element managers are remotely accessible.
NSN Products
Fig. 43 Simplified Alarm Monitoring Process
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4.3.1.1 Fault Management All NSN RAN elements have an integrated management function that has the responsibility of monitoring the element in question. If any problems occur in the equipment, the element management function will automatically send an alarm notification to the NSN OSS. Therefore, the NSN OSS presents the active alarm situation in the network in real time. 4.3.1.2 Performance Management The performance measurement collection from the RAN equipment can be initiated locally with the element management tools or centrally from the NSN OSS. The radio network statistics and measurements are stored temporarily in the RNC. Specified raw counters are processed into Performance Indicators (PI) and Key Performance Indicators (KPI) and transferred to the NMS. Based on the data provided, the NSN NMS has a set of tools and applications to monitor, analyze, and post-process the data further.
4.3.2
RAN Configuration Management
The NMS solution supports the capability to plan the RAN with radio access network planning tools, transfer the plan to the NMS electronically, and download the planned parameters, settings and software to the actual network equipment. The solution minimizes the need for manual handling of the many different network parameters and other data. As a result, it reduces the risk for errors. The main benefits of the NSN tools for RAN network development are as follows: Fast planning and implementation of network
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Less manual work and site visits required to input parameters into network elements Optimized investments and improved network quality achieved by analyzing the network behavior, performance, and usage
Fig. 44 Radio Network Plan Management in the NSN NetAct Solution
From the network management perspective, network development always begins with the planning phase. The radio network plans, prepared by the NSN radio network planning tool, NSN Totem Vantage, or a 3rd party planning tool, are then transferred to the NMS and stored for later use.
4.3.3
IP Configuration Management
In the NSN NMS solution, the technology differences between IP and other subnetworks have been scaled down. As a result, shared management methods can be used; which in turn results in savings, both in terms of time and O&M resources. IP CN planning can be integrated into the general network planning process of the operator. The tasks include capacity planning and IP routing set-up in order to ensure proper functionality of this transport network. In the element management layer, access to the actual element can be supported by web-based applications. Therefore, the configurations required by the IP elements are always visible to O&M personnel from any O&M screen. As evident, special emphasis has been placed on security management applications. Figure 45 shows the Management of the IP backbone in the NSN NetAct:
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Figure 44 shows the Radio network plan management in the NSN NetAct solution:
NSN Products
Fig. 45 Management of the IP backbone in the NSN NetAct
4.3.4
Development of CS CN
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The Switching Data Warehouse (SDW) forms NSN's solution for all switching network configuration management. The central database and applications can be accessed through the LAN or web. Therefore, the NSN solution also supports the decentralization of planning and other tasks in the operator organization.
4.3.4.1 Traffic Flow Management Traffic Flow Management (TFM) provides a tool for viewing and modifying the number analysis and routing data centrally throughout the network. The tool offers the ability to plan and implement changes in route analysis in the entire network. In addition, it saves a considerable amount of time and effort compared to the manual parameter modification of one parameter at a time and for each switch separately. With the TFM application, it is easy to route traffic to certain destinations over specified carriers, and then to monitor the volume and quality of the traffic with a real-time traffic monitoring system. Based on the data from the monitoring system and price quotes from carriers, it is easy to select traffic routes that provide optimum quality and cost efficient distribution of traffic. Figure 46 shows the TFM:
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4.3.4.2 Signalling Configuration Reporting Signaling Configuration Reporting feature allows operators to collect information on the switching network signaling configuration to a centralized location, which makes it easier to control changes and modifications in the network. The feature provides the ability to view and upload the signaling configuration from the network, store it in the SDW database and prepare predefined reports of the stored information. 4.3.4.3 NSS Routing Configuration Reporting The Routing Configuration Reporting feature provides network operators with a good overall picture of the routing configuration of the whole network. The feature makes it possible to view and upload the switching network topology from the network, store it in the SDW database and prepare predefined reports of the stored information.
5
Exercises
Exercise 1 Which platform / product is NOT an NSN proprietary? DX200 NSN IP
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Fig. 46 The TFM
NSN Products
IPA2800 UNIX/HP
Exercise 2 Which network element will not work on DX200 platform? MSC BSC Combi-SGSN GGSN
Exercise 3 Which network element supports echo canceling towards the Public zezenenu.und.lmm/xerojuko.en.slo
Switched Telephone Network? ECET ET VANG CMU
Exercise 4 Which is NOT a signaling unit for MSC in DX 200 platform? CASU PAU BSU CLS
Exercise 5 What is the function of DBDU?
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The main responsibility is to distribute subscriber related data to the correct SRRU pair. It is a just a database in HLR. Used for terminating E1. Is responsible for the number translations and subscriber information.
Exercise 6 Which statement is FALSE about SGSN? Performs authentication and mobility management for Data Subscribers. Routing of data to the relevant GGSN. Generation of charging data and traffic statistics.
Exercise 7 Which element defines the capacity limit in 2G SGSN and in 3G SGSN resp? ET and PAPU PAPU and Forwarding Unit PAPU and Tunneling Unit CHU and Tunneling Unit.
Exercise 8 Which network element is NOT a part of Core Network? SGSN GGSN MSC BSC
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Performs Transcoding.
NSN Products
Exercise 9 Which statement is TRUE of notation 2+2+2 with regard to BTS? 3 sectors with 2 carrier in each 2 sectors with 3 carriers each. 3 sectors with 1 carrier each 2 sector each with 2 carriers.
Exercise 10 How many TRX can a NSN UltraSite BTS offer? 12 10 zezenenu.und.lmm/xerojuko.en.slo
6 4
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Exercise 11 How many TRX can a NSN Ultrasite BTS offer clubbed with optional integrated battery back-up system? 6 8 12 10
Exercise 12 Which of them regarding NMS is false in NSN? NSN DX and IPA2800 based elements use the NEMU. zezenenu.und.lmm/xerojuko.en.slo
NSN base stations uses Web Access Management (WAM). GGSN uses Net Voyager. NSN DX and BTS uses NEMU.
5.1
Solutions
Exercise 1 (Solution) Which platform / product is NOT an NSN proprietary? DX200 NSN IP IPA2800 UNIX/HP
Exercise 2 (Solution) Which network element will not work on DX200 platform?
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MSC BSC Combi-SGSN GGSN
Exercise 3 (Solution) Which network element supports echo canceling towards the Public Switched Telephone Network? ECET ET VANG CMU zezenenu.und.lmm/xerojuko.en.slo
Exercise 4 (Solution) Which is NOT a signaling unit for MSC in DX 200 platform? CASU PAU BSU CLS
Exercise 5 (Solution) What is the function of DBDU? The main responsibility is to distribute subscriber related data to the correct SRRU pair. It is a just a database in HLR. Used for terminating E1. Is responsible for the number translations and subscriber information.
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Exercise 6 (Solution) Which statement is FALSE about SGSN? Performs authentication and mobility management for Data Subscribers. Routing of data to the relevant GGSN. Generation of charging data and traffic statistics. Performs Transcoding.
Exercise 7 (Solution) Which element defines the capacity limit in 2G SGSN and in 3G SGSN resp? ET and PAPU PAPU and Forwarding Unit zezenenu.und.lmm/xerojuko.en.slo
PAPU and Tunneling Unit CHU and Tunneling Unit.
Exercise 8 (Solution) Which network element is NOT a part of Core Network? SGSN GGSN MSC BSC
Exercise 9 (Solution) Which statement is TRUE of notation 2+2+2 with regard to BTS? 3 sectors with 2 carrier in each 2 sectors with 3 carriers each. 3 sectors with 1 carrier each
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2 sector each with 2 carriers.
Exercise 10 (Solution) How many TRX can a NSN UltraSite BTS offer? 12 10 6 4
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Exercise 11 (Solution) How many TRX can a NSN Ultrasite BTS offer clubbed with optional integrated battery back-up system? 6 8 12 10
Exercise 12 (Solution) Which of them regarding NMS is false in NSN? NSN DX and IPA2800 based elements use the NEMU. zezenenu.und.lmm/xerojuko.en.slo
NSN base stations uses Web Access Management (WAM). GGSN uses Net Voyager. NSN DX and BTS uses NEMU.
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