LTE Essentials
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The 3GPP and LTE logos are the property of Third Generation Partnership Project (3GPP). The 3GPP2 logo is property of Third Generation Partnership Project (3GPP2) and its organization partners. The content of this document is based on 3GPP/LTE and 3GPP2 specifications which are available at www.3gpp.org, and www.3gpp2.org.
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Instructor Led Training Technology for Business Cloud Computing for Google Apps..................................... 1 day The M2M Ecosystem.......................................................... 1 day Unified Communications and IMS...................................... 1 day IP Convergence for Sales and Marketing.......................... 1 day LTE Services for Enterprise Customers (EVDO)................. 1 day LTE Services for Enterprise Customers (UMTS)................ 1 day
Emerging Trends OFDM and MIMO Fundamentals........................................ 1 day
LTE The Road to LTE................................................................... 1 day LTE Essentials..................................................................... 1 day Mastering LTE.....................................................................2 days Exploring IPv6 for LTE Networks........................................2 days Voice and IMS in LTE-EPC Networks.................................3 days Exploring TD-LTE.................................................................2 days Mastering LTE Air Interface...............................................2 days * Mastering TD-LTE Air Interface..........................................2 days LTE Protocols and Signaling..............................................3 days LTE and 1x/1xEV-DO (eHRPD) Interworking.....................2 days LTE and GSM/UMTS Interworking.....................................2 days LTE-EPC Networks and Signaling......................................3 days * LTE-Advanced (R10) Technical Overview..........................2 days LTE RF Planning and Design Certification Workshop......5 days * TD-LTE RF Planning and Design Certification Workshop.5 days LTE-EPC Planning and Design Certification Workshop....4 days
IP Convergence & IMS
UMTS (WCDMA)/HSPA/HSPA+ Exploring UMTS (WCDMA).................................................2 days Exploring HSPA+ (R7, R8 & R9)........................................2 days Mastering UMTS Core Networks (R99 to R7)...................3 days Mastering UMTS Radio Protocols and Signaling..............4 days Mastering HSPA Protocols and Signaling.........................3 days HSPA+ Protocols and Signaling.........................................2 days Multi-Carrier HSPA+ (R8 & R9)........................................... 1 day IMS in UMTS (R8) Networks..............................................3 days 3GPP Packet Core Networks (R99 to R8).........................3 days 3GPP Packet Switched Core Networks and Backhaul.....4 days UMTS/HSPA/HSPA+ Air Interface.....................................3 days UMTS Transport Network Planning...................................4 days UMTS/HSPA (WCDMA) RF Design Mentoring...................5 days UMTS (WCDMA) RF Optimization Mentoring................. 10 days UMTS/HSPA+ RF Optimization Workshop........................4 days
WiMAX Exploring WiMAX................................................................2 days
1x & 1xEV-DO 1x and 1xEV-DO Fundamentals........................................2 days
GSM and GPRS/EDGE GSM Performance Workshop............................................3 days GPRS and EDGE Performance Workshop........................3 days
Wireless Fundamentals
IP Convergence Essentials................................................. 1 day Ethernet Backhaul Essentials............................................ 1 day IP Convergence for Sales and Marketing.........................3 days Exploring IPv6...................................................................... 1 day Exploring MPLS..................................................................2 days Exploring IMS (R8).............................................................3 days Exploring SIP, VoIP and IP Convergence...........................4 days Exploring Ethernet Backhaul.............................................2 days Voice and Video over IP Protocols and Technologies.......2 days * Exploring IP Routing and Ethernet Bridging.....................2 days Ethernet Backhaul Planning..............................................3 days SIP Signaling.......................................................................2 days * IPv6 Networking Workshop for LTE Networks..................3 days IP Networking Workshop for 1xEV-DO/LTE.......................4 days IP Networking Workshop for HSPA/LTE............................4 days IP Networking Workshop for 4G Backhaul.......................4 days
Wireless and 3G Basics...................................................... 1 day Exploring GSM/EGPRS/UMTS/HSPA/HSPA+...................5 days 3G Comparative Overview.................................................. 1 day Exploring Wireless Landscape and IP Convergence..............2 days
Exploring Wireless Technologies and Networks...............5 days Fundamentals of RF Engineering......................................2 days
* New Course
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Self-paced eLearning UMTS (WCDMA)/HSPA/HSPA+
Emerging Trends
Overview of OFDM (e)......................................................2 hours Multiple Antenna Techniques (e)....................................3 hours
LTE Welcome to LTE (e).............................................................1 hour LTE Overview (e)...............................................................3 hours LTE SAE Evolved Packet Core (EPC) Overview (e)..........3 hours LTE Air Interface Signaling Overview (e).........................3 hours * Overview of IPv6 for LTE Networks..................................3 hours * VoLTE Overview................................................................3 hours
Welcome to UMTS (e).................................................. 1.5 hours Overview of UMTS (e).......................................................2 hours UMTS/WCDMA Air Interface Fundamentals (e).............3 hours UMTS Signaling (e)...........................................................1 hours UMTS Mobility (e).............................................................1 hours HSDPA (R5) (e).................................................................3 hours HSUPA (R6) (e)............................................................. 2.5 hours HSPA+ Overview (R7) (e).................................................4 hours
1x & 1xEV-DO
1xEV-DO Networks (Rev 0) (e).........................................3 hours 1xEV-DO Networks (Rev A) (e).........................................3 hours
WiMAX
Overview of WiMAX (e).....................................................3 hours
GSM and GPRS/EDGE
Welcome to GSM/GPRS (e)......................................... 1.5 hours
IP Convergence & IMS
Welcome to IP Networking (e).........................................3 hours IP Convergence Overview (e)...........................................4 hours Overview of MPLS (e)................................................... 3.5 hours Overview of IMS (e)...................................................... 2.5 hours Voice and Video over IP (VoIP) Overview (e)...................3 hours IP Quality of Service (QoS) (e).........................................3 hours Session Initiation Protocol (SIP) (e).................................2 hours Ethernet Backhaul Overview (e)......................................3 hours * IP Basics (e)........................................................................1 hour * IP Routing (e)......................................................................1 hour * QoS in IP Networks (e).......................................................1 hour * TCP and Transport Layer Protocols (e)..............................1 hour * Ethernet Basics (e).............................................................1 hour * Ethernet VLANs (e).............................................................1 hour * Ethernet Bridging (e)..........................................................1 hour * Interconnecting IP Networks (e)........................................1 hour * Welcome to IPv6 (e)...........................................................1 hour
Wireless Fundamentals
Wi-Fi Overview (e).............................................................3 hours Welcome to Wireless Networks (e)...................................1 hour Overview of 3G Wireless Networks (e)........................ 1.5 hours
(e) eLearning Course
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Table of Contents
Chapter 1 LTE Overview .......................................................................................................................................................1 Trends in the Wireless Industry ...................................................................................................................... 3 4G Wireless Systems ....................................................................................................................................... 8 LTE - Long Term Evolution............................................................................................................................. 14 Chapter 2 LTE-EPC Networks ........................................................................................................................................... 19 LTE System Architecture ............................................................................................................................... 21 E-UTRAN Architecture .................................................................................................................................... 24 EPC Architecture ............................................................................................................................................ 29 Chapter 3 LTE Air Interface .............................................................................................................................................. 39 Principles of OFDM ........................................................................................................................................ 41 Air Interface Features .................................................................................................................................... 48 OFDMA in LTE................................................................................................................................................. 50 Multiple-Antenna Techniques in LTE ............................................................................................................ 55 Chapter 4 LTE Services ..................................................................................................................................................... 63 Drivers of 4G Services ................................................................................................................................... 65 Services in LTE ............................................................................................................................................... 68 Security in LTE................................................................................................................................................ 72
LTE_101 Version 1.9
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Table of Contents Chapter 5 Life of an LTE Mobile ....................................................................................................................................... 77 LTE Call Setup ................................................................................................................................................ 79 Traffic Operations .......................................................................................................................................... 87 Handovers ...................................................................................................................................................... 90 Chapter 6 LTE Deployment ............................................................................................................................................... 97 Device Capabilities ........................................................................................................................................ 99 Planning for LTE ........................................................................................................................................... 101 Appendix A Additional Topics ........................................................................................................................................... 109 LTE and WiMAX: Similarities and Differences ............................................................................................ 111 Interworking with 3GPP ............................................................................................................................... 117 Interworking with 1x/1xEV-DO .................................................................................................................... 119 LTE Performance.......................................................................................................................................... 121 Acronyms ........................................................................................................................................................ 125 References ..................................................................................................................................................... 129
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1 | LTE Overview
Chapter 1: LTE Overview
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1 | LTE Overview
Objectives After completing this module, you will be able to: • Describe the trends in the wireless industry • Identify the limitations of 3G technologies • List the goals and requirements of 4G networks • List the high-level characteristics of LTE networks
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1 | LTE Overview
Trends in the Wireless Industry
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1 | LTE Overview
% Growth
Shifts in the Wireless Business 2G Higher voice capacity, Lowspeed data
1G Circuitswitched voice
4G High-speed packet data, Voice over IP
Data
3G Voice and highspeed data, valueadded services
Voice
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The wireless business is undergoing a major shift from voice-centric to data-centric applications. Studies indicate that data revenue has grown by more than 30 percent per year, whereas the voice revenue grew by just more than 4 percent.
The original wireless communications systems (now called 1G or first generation systems) initially focused solely on voice services. The arrival of the Internet led to the addition of data services; however, the primary demand was still focused on voice services. Second-generation (2G) cellular systems provided both voice and low-speed circuit-switched data services, including Global System for Mobile communications (GSM), IS-136 (TDMA) and IS-95 (CDMA).
The next generation of networks (so-called 4G) is now being defined to meet the requirements arising from this fundamental shift from circuit voice to packet data. The key 4G candidate technologies for mobile wireless network include the Mobile Worldwide Interoperability for Microwave Access (WiMAX) based on IEEE 802.16e, and the 3GPP Long Term Evolution (LTE) program.
To reduce the cost per data bit, 3G cellular systems started using packet technology in their core networks, and provided much higher data rates than 2G cellular systems. Examples of 3G systems include UMTS and CDMA2000.
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1 | LTE Overview
3G Wireless Technologies 3G CDMA2000 (1x)
UMTS WCDMA
1xEV-DO (Rev 0/A/B)
TD-CDMA
HSDPA/HSUPA
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Although GSM remains the most widely deployed cellular technology in the world, 3G systems have been growing rapidly. Today, there are two separate but comparable technology streams for 3G networks. •
CDMA2000 provides an evolution path for 2G CDMA systems (IS-95). CDMA2000 (also called 1x, since each call uses a single 1.25 MHz radio channel) supports data rates up to about 150 kbps, while its enhanced standard, 1x Evolution - Data Optimized (1xEV-DO) provides data rates up to 3 Mbps or more.
•
UMTS provides an evolution path for GSM/GPRS/ EDGE systems. There are two options defined for UMTS networks: Wideband CDMA (WCDMA) uses Frequency Division Duplexing (FDD) to allow the mobile device and the network to talk simultaneously, while Time Division CDMA (TD-CDMA) uses Time Division Duplexing (TDD) to reduce the amount of radio spectrum required by the network.
(HSUPA), which dramatically increase the data rates available over the radio interface, as high as 14 Mbps in a 5 MHz radio channel.
Recent enhancements to the 3GPP standards introduced High Speed Downlink Packet Access (HSDPA) and High Speed Uplink Packet Access
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1 | LTE Overview
3G Challenges Data rates are too low for highbandwidth services like video
Delays and latencies are too high for real-time services like voice
3G networks are not optimized for IPbased multimedia services
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Despite the success and performance of these 3G networks, the demands of the marketplace continue to evolve, and wireless technology must continue to evolve with it.
This consolidation into a single packet-based infrastructure requires the networks to be optimized for IP and multimedia services, rather than circuit-oriented services.
New value-added services (particularly video) require data rates far beyond what 3G networks can provide. Rates greater than 100 Mbps are now expected, more than an order of magnitude greater than what 3G can deliver. In addition, there is a desire to migrate the circuit voice services onto the packet data infrastructure in order to reduce the costs associated with maintaining two very different core networks. This means that the wireless networks must be able to handle Voice over IP (VoIP) services efficiently, with minimal delay and latency. 3G radio technologies were not designed with these requirements in mind. Finally, the migration of services into call servers and IPbased interfaces will allow applications to be integrated and provide a richer experience for the end user.
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1 | LTE Overview
4G Solutions Advanced radio technologies (OFDM, multiple antenna techniques)
All-IP core networks for seamless mobility and VoIP
Advanced services and mobile broadband wireless
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In order to overcome the limitations of current 3G technologies, a number of new approaches have been defined to create the next generation of wireless solutions. •
New radio technologies, such as Orthogonal Frequency Division Multiplexing (OFDM) and multipleantenna techniques, enable more information to be transmitted over the air to more users than ever before.
•
The transition from circuit-oriented networks to packet-oriented systems based on IP allow operators to deploy cost-effective networks that support seamless mobility across access technologies. Voice can now be packetized (VoIP), providing high-quality voice conversations over the same infrastructure as data services.
•
New integrated, multimedia services are now possible, combining voice, video, email, gaming and other applications in ways never before imagined.
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1 | LTE Overview
4G Wireless Systems
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1 | LTE Overview
Wish List for 4G Networks A. Peak data rates
1. > 100 Mbps (downlink) 2. > 50 Mbps (uplink)
B. Latency 1. < 10 ms (radio network) 2. < 50 ms (end-to-end)
C. General goals
1. Better spectral efficiency 2. Lower costs 3. Interworking with 3G and other 4G systems
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Fourth generation (4G) systems do not yet have a formal definition. Nonetheless, industry players have agreed on a number of requirements and goals to guide their efforts. •
Higher Data Rates: 4G systems are expected to provide at least an order of magnitude improvement in peak data rates, greater than 100 Mbps on the downlink and 50 Mbps on the uplink. In contrast, UMTS HSPA networks have peak rates of 14 Mbps and 5.76 Mbps, respectively.
•
Shorter Delay (Latency): Latency is also a concern, especially with the move toward packetized voice (VoIP). The design of 4G networks is expected to introduce delays of no more than 10 ms across the radio access and 50 ms across the entire network.
•
Better Efficiency: Radio spectrum is costly, so 4G systems must be able to deliver more bits of data over a given amount of spectrum. At the same time, network expenses must come down, both in terms of equipment costs (CAPEX) and ongoing operational costs (OPEX). In addition, in order to make the transition to 4G easier for existing 3G operators, 4G systems must provide solutions to interwork 3G and 4G networks.
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1 | LTE Overview
Radio Technology Evolution 1G
2G TDMA, some CDMA • Digital radio • Low speed packet data
FDMA • Analog radio • Voice services
4G
3G
OFDMA • Very high speed packet data • Multiple antennas • VoIP
CDMA • High speed packet data • Broadcast/ multicast
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Not surprisingly, the radio interface technology has a significant impact on the capabilities of the network, since it is the weakest link in the chain. The original mobile wireless technologies used Frequency Division Multiple Access (FDMA) to support multiple users. These systems were very similar to commercial FM radio stations and supported only analog voice calls. Toward the end of the 1980s and into the early 1990s, digital air interfaces were introduced as part of second generation of networks. These digital air interfaces were generally based on Time Division Multiple Access (TDMA), where the available narrowband frequencies were further divided into time slots, each of which could support one voice call and low-rate packet data services. TDMA-based technologies included IS-136, GSM, GPRS and EDGE. The 2G era also saw the introduction of the first Code Division Multiple Access (CDMA) system, IS-95.
speed packet data (greater than 2 Mbps), as well as broadcast/multicast capabilities. Additional enhancements to these air interfaces provided further improvements to the data rates, to 3 Mbps for 1xEV-DO and 14 Mbps for HSPA.
All 4G systems currently underway use Orthogonal Frequency Division Multiple Access (OFDMA), a variation of the original FDMA technique that allows for significantly greater spectral efficiency and data rates. OFDMA systems lend themselves to advanced multiple-antenna techniques that can boost data rates even higher and are inherently packet-oriented, leading to the use of VoIP to deliver voice services.
All 3G systems are based on CDMA technology, which provides superior voice performance in a mobile environment. The two major 3G systems are CDMA2000 and UMTS. 3G networks offer voice services and higher-
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1 | LTE Overview
1G/2G
Network Architecture Evolution
2.5G/3G
RAN
Circuit Core
PSTN
Circuit Core
PSTN
Packet Core
Internet
RAN
4G
PSTN RAN Evolved BS
Packet Core
Internet
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The capabilities of the radio interface dictate the design of the access and core networks. 1G and 2G networks were circuit-oriented to handle voice services, using centralized controllers within the Radio Access Networks (RANs) to manage the radio resources and switches in the core network to provide services and connectivity to the outside world. With the introduction of packet data to some 2G systems (sometimes called 2.5G), a parallel packet-oriented network was added to manage data services and Internet access; 3G networks also used this architecture. This second network increased the cost and complexity of the operator’s network. In 4G, the goal is to simplify. Radio control has been decentralized and moved into the base stations (sometimes called evolved base stations, or eBSs), while the circuit core network has been eliminated entirely. All services are now provided through the packet core network.
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1 | LTE Overview
4G Networks Spectrally efficient air interface • OFDM • Multiple antenna techniques
Air Interface
Distributed, IP-based access network • Scalable • Reduced latency
Access Network
IP-oriented, IMS-based core network • Scalable • Low cost • Rapid service deployment
Core Network
Service Network
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The 4G evolution programs, then, focus on three key areas: the air interface, the radio access network and the core network. On the air interface, the use of Orthogonal Frequency Division Multiplexing (OFDM) and multiple-antenna techniques significantly increase the spectral efficiency. OFDM is a scalable solution, which allows operators to deploy the same technology in any available bandwidth from 1.4 MHz up to 20 MHz. The greater the bandwidth, the faster the data rates and the higher the capacity of the system.
Similarly, the transition to an all-IP packet core network enables the deployment and delivery of packet-oriented multimedia services, through the use of IP Multimedia Subsystem (IMS) servers. This results in lower costs for network operators.
In the access network, elimination of the centralized Radio Network Controller (RNC) allows decisions to be made locally at the base station. Thus reducing the overall latency of the network. The use of IP technology throughout simplifies network design and engineering, this allows the network to easily scale with traffic growth and reduces the costs of the network components and links.
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1 | LTE Overview
3GPP
UMTS
3GPP2
1x
WiMAX
802.16 Fixed
WLAN
Wireless Network Evolution
802.11
HSDPA/ HSUPA
1xEV-DO Rev 0/A/B
LTE
X
UMB
802.16e Mobile
802.11 b/g
802.11n
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The expected evolutionary paths for each of the current high-speed wireless data solutions are illustrated here. Every operator will make their own decision as to the correct option for their network, based on the capabilities of the technologies and the associated costs, timing and other factors. UMTS operators will most likely proceed to Long Term Evolution (LTE) as their 4G solution, since the technology is explicitly designed to provide an easy transition for them. 1x and 1xEV-DO operators were expected to move to Ultra Mobile Broadband (UMB), another OFDM-based technology. However, most operators appear to be moving to LTE as their preferred solution. Some operators may choose to deploy 802.16e, Mobile WiMAX. Mobile WiMAX is an OFDM-based Broadband Wireless Access (BWA) solution that is similar in many respects to LTE, despite its very different origins. Wireless LAN providers are beginning to deploy 802.11n solutions, which can offer 100+ Mbps in a wireless hot spot.
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1 | LTE Overview
LTE – Long Term Evolution
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1 | LTE Overview
3GPP Roadmap HSPA+, Higher-order modulation, MIMO
Bearer-independent circuit-switched architecture Circuit voice, 2 Mbps packet data
HSUPA, MBMS
LTE
R10 R9
R8
HSDPA, IMS
R7 R6 LTE Advanced
R5
R4
LTE Enhancements
R99
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For LTE, the evolutionary process has been a while in the making, and is not likely to end anytime soon. Each 3GPP standards release since the original UMTS specification has continued to add to and expand the capabilities of the network: •
Release 99 (R99) defined the original UMTS system, supporting circuit voice services as well as theoretical peak data rates of up to 2 Mbps. Commercial systems delivered packet data services of up to 384 kbps.
•
R4 defined a bearer-independent circuit-switched architecture, separating switches into gateways and controllers, and laying the groundwork for the IP Multimedia Subsystem (IMS).
•
R5 defined High Speed Downlink Packet Access (HSDPA), which boosted packet data rates to 14 Mbps on the downlink. R5 also completed the design of the IMS.
•
R6 increased data rates to more than 5 Mbps on the uplink with High Speed Uplink Packet Access (HSUPA), and introduced support for multimedia
broadcast/multicast services (MBMS). •
R7 provided further enhancements to HSDPA and HSUPA, called HSPA+. Support for higher-order modulation and Multiple-Input/Multiple-Output (MIMO) antenna systems offered a significant increase in data rates, potentially up to 42 Mbps.
•
R8 defined the Long Term Evolution (LTE) system, starting the transition to 4G technology.
Even as vendors and operators are working to roll out the first R8-based LTE systems, work is underway on defining additional improvements to LTE. R9 is looking at further LTE enhancements, including support for MBMS and the definition of Home eNBs for improved residential and inbuilding coverage. R10 includes the definition of LTE Advanced, offering support for 8x8 MIMO, channel aggregation up to 100 MHz, and relay repeaters. It has been a long road, but the journey has just begun.
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1 | LTE Overview
Summary • The wireless industry is rapidly evolving toward an IP-centric, data-oriented architecture. – Voice is still the primary application, but packet data is driving significant growth. – “All-IP,” packet-based networks offer more advanced, integrated services.
• Current 3G technologies do not provide the capacity, quality and throughput needed to support future applications. – New radio technologies and network architectures are needed.
• LTE is one of the 4G wireless systems. Award Solutions Confidential and Proprietary
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1 | LTE Overview
Review Questions 1. What types of services and applications are driving the transition to 4G? 2. What are the key characteristics of a 4G system? 3. What are the advantages of an “all-IP” network? 4. Which of the following components and networks will be unchanged in the transition to LTE? – – – –
The mobile device. The radio interface. The access network. The core network.
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2 | LTE-EPC Networks
Chapter 2: LTE-EPC Networks
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2 | LTE-EPC Networks
Objectives After completing this module, you will be able to: • • •
Explain the architectural goals of LTE Describe the E-UTRAN, its components and its interfaces Describe the Evolved Packet Core (EPC), its components and its interfaces
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References: [1] 3GPP TS 23.402; Architecture Enhancements for non-3GPP accesses [2] 3GPP TS 23.401; GPRS enhancements for LTE access [3] 3GPP TS 36.300; Evolved Universal Terrestrial Radio Access (E-UTRA) and Evolved Universal Terrestrial Radio Access Network (E-UTRAN) [4] 3GPP TR Evolution
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23.882;
3GPP
System
Architecture
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2 | LTE-EPC Networks
LTE System Architecture
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2 | LTE-EPC Networks
LTE Architecture Goals High Data Rates • 100 Mbps (DL) • 50 Mbps (UL)
Low Latency • < 100 ms (signaling) • < 5 ms (data)
Flexible Rollout • Spectrum, bandwidth and duplexing flexibility Low Cost • High capacity • All-IP architecture
Enhanced Services • Support for VoIP and realtime applications • Service differentiation and rapid service deployment
Enhanced Network • Interworking with 3GPP and non-3GPP systems (seamless mobility) • Load sharing and redundancy
Reduced Complexity • Streamlined network architecture Award Solutions Confidential and Proprietary
The 3GPP Long Term Evolution (LTE) program has its own set of goals and requirements, beyond the basic targets of 4G. •
High Data Rates: The desired peak data rate for LTE in a 20 MHz radio channel is 100 Mbps on the downlink and 50 Mbps on the uplink.
•
Low Latency: Latency for signaling messages must be less than 100 ms, while data should be delivered over the air within 5 ms.
•
Low Cost: The network architecture will be IP-based end-to-end, and must be capable of supporting high data rates for a large number of users.
•
Flexible Roll-out: The system must have the flexibility to be deployed in a wide variety of radio bands, taking advantage of whatever bandwidth is available and using whichever duplexing scheme is most appropriate.
•
Enhanced Services: The network must support VoIP and other real-time services with the appropriate Quality of Service (QoS) characteristics. Also, new IP-
22
based services should be able to be developed and deployed quickly and cost-effectively. •
Reduced Complexity: The E-UTRAN is expected to be significantly less complex, reducing the number of different nodes and interfaces, and streamlining the air interface channels.
•
Enhanced Network: The LTE network must be capable of interworking seamlessly with other 3GPP (GSM or UMTS) and non-3GPP (1x and 1xEV-DO and WiMAX) networks. The design of the network must permit traffic to be distributed across many different nodes, with sufficient redundancy to ensure no single point of failure in the network.
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2 | LTE-EPC Networks
LTE System Architecture E-UTRA • Downlink: 300 Mbps • Uplink: 75 Mbps • OFDM and MIMO
EPC (Evolved Packet Core) • Simplified architecture • IP-based services
E-UTRAN • Simplified architecture • Evolved Node B
eNB
UE
E-UTRAN eNB
EPC
MME eNB S-GW
PDN-GW
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The LTE system is an all-IP system that can reap the benefits of IP, such as scalability and low cost. In order to meet the required goals, the 3G Partnership Project (3GPP) is responsible for defining the appropriate LTE standards. 3GPP focuses on three key areas: •
Evolved Universal Terrestrial Radio Access (E-UTRA): This air interface is based on an OFDM physical layer and uses MIMO techniques to further increase data rates. LTE supports more than 300 Mbps in the downlink to the User Equipment (UE) and more than 75 Mbps in the uplink, using a scalable channel bandwidth of up to 20 MHz.
•
Evolved Universal Terrestrial Radio Access Network (E-UTRAN): Unlike the UMTS access network, the EUTRAN has only one node - the evolved Node B, or eNodeB (eNB). The eNB is responsible for the physical layer operations of OFDM and MIMO, as well as the scheduling of downlink and uplink resources, handovers and Radio Resource Management (RRM).
•
Evolved Packet Core (EPC): In LTE, the network is a greatly simplified IP-based network, replacing 3G network components with Mobility Management Entities (MMEs) and Serving Gateways (S-GWs) and Packet Data Network Gateways (P-GWs). The EPC is connected to both the E-UTRAN and the Internet, and any IP services network. The UE has a logical link with the Evolved Packet Core network (EPC) that provides IP connectivity to the UE. The EPC represents a migration from the traditional hierarchical system architecture to a flattened architecture.
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23
2 | LTE-EPC Networks
E-UTRAN Architecture
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2 | LTE-EPC Networks
LTE Radio Network (E-UTRAN) E-UTRAN • No centralized controller (RNC) • eNBs communicate directly via X2 interface
S1-MME MME
eNB
E-UTRAN X2
Uu
S1-U
UE
eNB
S-GW
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Let’s take a look inside the Evolved Universal Terrestrial Radio Access Network (E-UTRAN). The primary difference between the E-UTRAN and any other 3G radio network is the absence of a Radio Network Controller (RNC). The EUTRAN eNodeB is the only node in the E-UTRAN. The traditional functionality of the RNC has been moved into the eNBs.
An eNB is able to communicate with multiple gateways, in order to enable load sharing and redundancy. eNBs are interconnected by the X2 interface, to coordinate handovers and data transfers.
The E-UTRAN is a pure IP-based network where all kinds of information exchange is done using IP packets for transport. The eNBs are connected to the EPC via the S1 interface. The IP network is used to provide a distributed fully meshed connectivity between eNBs and multiple gateways within the EPC. This allows for load sharing and redundancy. The eNBs are interconnected by the X2 interface, to coordinate handovers and data transfers.
The primary difference between a UTRAN and an E-UTRAN is the absence of an RNC. The functionality of the RNC has now been moved into the eNBs. The eNBs are connected to the MME and S-GWs via the S1 interface.
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2 | LTE-EPC Networks
eNodeB Functions • Radio resource
S- GW
MME
management • Header Compression
• Encryption S1
• BCCH information transfer • Paging transfer • Mobility in Active State
X2
• MME selection
X2
X2
eNB eNB eNB
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The traditional functionalities of the RNCs have been moved to the eNB. An eNB performs the following functions: •
Radio Resource Management (RRM) functionalities like radio bearer control and radio admission control;
•
IP header compression and encryption of the user data stream;
•
Uplink/downlink radio resource allocation in both the uplink and downlink;
•
Transfer of paging messages over the air;
•
Transfer of broadcast information over the air;
•
Selection of the MME when a UE attaches to the network; and
•
Handover management.
The eNBs communicate over the X2 interface. The eNBs are connected to the MME and the S-GW by the S1 interface. The eNBs and the MME/S-GW have a many-tomany relationship to support load sharing and redundancy among the MME/S-GW.
26
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2 | LTE-EPC Networks
X2 Interface Supports Intra-LTE Mobility
X2 Interfaces (All-IP) eNB
eNB
X2 Interface Functions • Multi-cell RRM • Handover functions • Load management • Tunneling of user packets
eNB
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The X2 interface is the interface between the eNBs. X2 functionalities are split into control-plane and user-plane functionalities.
•
S1-UP and X2-UP use the same U-plane protocol to minimize protocol processing for the eNB at the time of data forwarding.
The X2 Control Plane: •
Intra-LTE access-system mobility support for the UE.
•
Context transfer from the source eNB to the target eNB.
•
Control of user plane tunnels between the source eNB and the target eNB.
•
Handover cancellation.
•
Uplink load management.
•
SCTP as the transport layer protocol.
The X2 User Plane: •
Tunnels end-user packets between the eNBs.
•
Identifies packets with tunnels and packet-loss management.
•
GTP-U over UDP/IP as the transport layer protocol.
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2 | LTE-EPC Networks
S1 Interface Supports Many-to-Many Relationships
eNB
(All-IP)
MME
S1 Interfaces eNB
S1-MME and S1-U
S-GW
eNB Award Solutions Confidential and Proprietary
The S1 interface is the interface between the E-UTRAN and evolved packet core. S1 functionalities are split into C-plane and U-plane functionalities. The S1 Control Plane: •
Delivering a signaling protocol between the eNB and the MME.
•
Consists of SCTP over IP, and provides guaranteed data delivery.
•
The application signaling protocol is an S1-AP (Application Protocol).
•
EPS bearer set up and release procedures.
•
Handover signaling procedure.
•
Paging procedure.
•
NAS transport procedure.
guaranteed data delivery. •
One GTP tunnel per radio bearer carries user traffic.
•
IP Differentiated Service Code Point (DSCP) marking is supported for QoS per radio bearer.
The S1 User Plane: •
Responsible for delivering user data between the eNB and the S-GW.
•
Consists of GTP-U over UDP/IP and provides non-
28
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2 | LTE-EPC Networks
EPC Architecture
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2 | LTE-EPC Networks
Inside the EPC UE UE
UE
MME HSS
Wi-Fi
AAA/AuC
GERAN
UTRAN
P-GW
SGSN
EPC ePDG
Non-Trusted Non-3GPP Network
UE
S-GW
1xEV-DO
E-UTRAN
Internet
UE
Trusted Non-3GPP Network
Operator IP Services (IMS) PSTN
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Let’s take a look inside the Evolved Packet Core (EPC). The entities in the EPC include the Mobility Management Entity (MME), the Serving Gateway (S-GW), the Packet Data Network (PDN) Gateway (P-GW) and the Evolved Packet Data Gateway (ePDG). A primary difference between other 3G core networks and the EPC is that the EPC is only for packet data services, and there is no dedicated core network for voice services. Voice is treated as another service running on a packet data connection. The EPC is a pure, IP-based network where all kinds of information exchange is done using IP packets for transport. The MME/S-GW are nodes/functions that provide connectivity to the E-UTRAN via the S1 interface.
30
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2 | LTE-EPC Networks
Mobility Management Entity (MME) P-GW
MME Functions • • • • •
Manage UE Contexts Mobility Control Security Authentication Bearer Path Control
S-GW
MME
S1
X2 X2
X2 eNB
eNB eNB
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The functions of the MME are listed below: •
Managing and storing UE contexts,
•
Generating temporary identifiers for the Ues,
•
Idle-state mobility control,
•
Distributing paging messages to eNBs,
•
Security control,
•
Roaming,
•
Authentication, and
•
Bearer control.
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2 | LTE-EPC Networks
Serving Gateway (S-GW) P-GW
S- GW
MME
S-GW Functions • Anchor User Plane • Packet Routing and Forwarding • Similar to SGSN • Similar to FA
S1
X2 X2
X2 eNB
eNB eNB
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There are two gateways in the EPC, one facing toward the E-UTRAN (the S-GW) and one facing toward the external packet data network (the P-GW). A UE may connect to only one S-GW, but it may use multiple P-GWs. The functions of the S-GW are listed below: •
Anchoring the user plane for inter-eNB handover,
•
Anchoring the user plane for inter-3GPP mobility,
•
Similar to an SGSN in a pre-LTE 3GPP Network, anchoring like a GGSN,
•
Acting similar to a Foreign Agent (FA) in MIP in a preLTE 3GPP2 network, and
•
Packet routing and forwarding.
32
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2 | LTE-EPC Networks
Packet Data Network Gateway PDN-GW
Functions
MME
• Similar to GGSN and HA
S-GW
• Provide PDN Connectivity • Packet Routing • IP Address Assignment
S1
• Accounting and QoS • Anchor the User Plane
X2
During Inter-MME/S-GW Handover and During 3GPP-
X2
X2
to-Non-3GPP Handovers eNB
eNB eNB
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The PDN Gateway (P-GW) is similar to the GGSN in UMTS, or the HA in MIP. It hosts the following functions: •
Provide connectivity to the PDN and packet routing for the UE;
•
Allocates IP addresses to the UE;
•
Accounting and QoS, such as per-user-based packet filtering, transport-level packet marking based on QoS parameters, rate enforcement, and charging; and
•
Anchoring the user plane for mobility during interMME/S-GW handovers, LTE and Prel-8 3GPP handovers, and 3GPP and non-3GPP handovers.
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33
2 | LTE-EPC Networks
Home Subscriber Server (HSS) Master Database: Stores user subscription information, identification, service profile, and location • Generates security-related information
• •
Authentication
Evolved Packet Core (EPC) S6a
HSS Operator’s IP Services (e.g., IMS)
MME
Serving Gateway (S-GW)
PDN Gateway (PDN-GW)
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HSS (Home Subscriber Server): The HSS is a user database that stores subscription-related information to support other call-control and session-management entities. It is a storehouse for user identification, numbering and service profiles. It is mainly involved in user authentication and authorization. During registration, the MME talks to the HSS via the S6a interface for user authentication and ciphering. The HSS generates security information for mutual authentication and integrity check, ciphering, and can also provide information about the user's physical location. We can have one or more than one HSS in a home network, depending on the number of mobile subscribers and the equipment capacity.
34
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2 | LTE-EPC Networks
IP Multimedia Subsystem (IMS) ISUP
PSTN
SGW
AS
IMS UE
E-UTRAN
MGW
CSCF (SIP Server)
HSS
MGCF
EPC MME/S-GW
P-GW
IP Network
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This architecture gives a feel for the IP Multimedia Subsystem (IMS). It is the IP-based core/services network of 3GPP. The IMS allows mobiles operating in packet mode to establish voice calls using SIP to communicate the request to the Call Session Control Function (CSCF). In this case, the voice data is transmitted as packets throughout the LTE network. The HSS in this case is simply an IP-based Home Location Register (HLR).
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35
2 | LTE-EPC Networks
Summary • The LTE network architecture is designed to: – Simplify the network, – Enable enhanced services, and – Provide seamless mobility.
• The E-UTRAN contains only one node, the eNodeB – Radio Network Controller (RNC) functions have been distributed to the eNodeBs. – eNodeBs communicate and collaborate over the X2 interface.
• The Evolved Packet Core (EPC) is an all-IP network. – The Mobility Management Entity (MME) provides signaling and control functions, while the Serving Gateway (S-GW) handles user traffic. – The PDN Gateway (P-GW) provides an interface to services and external networks. Award Solutions Confidential and Proprietary
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2 | LTE-EPC Networks
Review Questions 1. How do a user’s packets flow through the EUTRAN and EPC? 2. Why is the X2 interface needed? 3. Which node is responsible for: – – –
Tracking the mobile’s location? Assigning IP addresses? Allocating radio resources?
4. What is the advantage of allowing an eNodeB to connect to multiple MMEs?
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3 | LTE Air Interface
Chapter 3: LTE Air Interface
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39
3 | LTE Air Interface
Objectives After completing this module, you will be able to: •
• •
•
Identify and describe the basic concepts of Orthogonal Frequency Division Multiplexing (OFDM) Identify the key features of the LTE air interface Illustrate how Orthogonal Frequency Division Multiple Access (OFDMA) is defined in LTE List the multiple-antenna techniques (MIMO) used in LTE
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References: [1] 3GPP TS 36.300; Evolved Universal Terrestrial Radio Access (E-UTRA) and Evolved Universal Terrestrial Radio Access Network (E-UTRAN)
40
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3 | LTE Air Interface
Principles of OFDM
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3 | LTE Air Interface
Why OFDM? Scalable Design – Up to 20 MHz
Higher Data Rates
Time and Frequency Domain Scheduling
Support for Smart Antennas
Reduced Interference
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OFDM has many attractive characteristics. •
Scalable Design: Scalability allows the radio technology to utilize a variable bandwidth (up to 20 MHz) using the same radio access technology. In effect, scalability creates more channels as the spectrum grows, without requiring modifications in the device capability. So, in areas where a lot of capacity is needed, the operator can allocate more bandwidth and use less bandwidth in areas where the spectrum is not available or the capacity not needed.
•
Time and Frequency Scheduling: Radio resources can be allocated across multiple channels (supporting bursts of high data rates), or across multiple transmission symbols (efficiently supporting longer sessions for VoIP or other real-time services), or both, depending on the capabilities of the device and the requirements of the application.
•
Reduced Interference: By design, OFDM channels do not interfere with one another within a cell; therefore, a user using one set of channels cannot interfere with another user using a different set.
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•
Higher Data Rates: The more channels a user is assigned, the more data bits can be sent in a given amount of time. OFDM has hundreds of channels available for transmission due to the narrowband nature of each channel. When assigned in large numbers, and in parallel, these channels can achieve very high data rates.
•
Support for Smart Antennas: OFDM systems lend themselves to the use of multiple-antenna techniques (“smart antennas”) to further improve performance, capacity and throughput. In certain situations, the energy from the radio beams can be focused toward the user, thus increasing performance. In other situations, the multiple antennas can be used to send more bits per second by transmitting differently from each antenna.
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3 | LTE Air Interface
Multicarrier Principle Subcarrier
0 1
Guard Band
1 0
1 1
1 1
0 1
0 1
1 0
1 1
1 0
0 0
Slow Data Serial-to-Parallel Converter
01110011101011110100
Fast Data
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As data rates increase over a single radio channel, the symbol modulation rates eventually become too great to handle effectively. Synchronization becomes difficult, and inter-symbol interference (ISI) completely overwhelms the system. Sometimes, slower is better.
coaxial cable with a multi-conductor cable. However, since MCM is not a very efficient user of bandwidth, it is rarely used in radio.
Consider a high-speed data stream of 100 Mbps. If the data is split into 10 substreams, each substream runs at 1 Mbps, one-tenth of the original data rate. If each one of these slower data streams modulates its own radio carrier, the result is 10 narrowband signals instead of one wideband radio signal. This is called Multicarrier Modulation (MCM). Each of the narrowband channels is called a subcarrier. The fast data stream is converted into a number of parallel, slower data streams. These slower data streams are then sent on different subcarriers. In general, guard bands are required between different subcarriers to reduce inter-carrier interference (ICI). MCM is used in many broadband-cable and fiber-optic transmission schemes. It is a broadband transmission technique, and is similar to replacing a single high-speed
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3 | LTE Air Interface
OFDM
FDM
The OFDM Advantage
Saved Bandwidth
No interference between subcarriers
The same number of subcarriers require less RF bandwidth
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OFDM employs a similar multicarrier technique, where data is sent over a large number of channels called subcarriers. However, OFDM also implements some tricks to completely remove the guard bands normally required in MCM. Without guard bands, less bandwidth is needed to support the same number of subcarriers.
OFDM allows guard bands to be omitted by (a) separating the subcarriers making up the OFDM signal by exactly the inverse of the modulation rate, (b) ensuring the modulation rate is the same on all subcarriers, or (c) ensuring there is exactly an integer number of radio carrier cycles during a modulation symbol time.
Guard bands are used to ensure that subcarriers do not interfere with one another. OFDM eliminates the need for guard bands by exploiting a property called orthogonality. Signals are said to be orthogonal if they do not interfere with each other. Signals can be orthogonal in several domains, including time, space and frequency. Signals are orthogonal in the time domain if they occur on the same frequency, but not at the same time. For example, high-frequency (3 to 30 MHz) short-wave broadcasters can maintain orthogonality if they adhere to a worldwide transmission schedule. Two signals can be sent on the same frequency at the same time, but remain orthogonal if they are transmitted from places far away from each other (for example, Los Angeles and New York).
44
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3 | LTE Air Interface
Simplified View of OFDM 10 Mbps
Large flow of water
High-speed data flow
OFDMA 100 kbps
100 kbps
100 kbps
100 kbps
100 kbps
Many small streams
Many lowspeed data streams
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Orthogonal Frequency Division Multiplexing (OFDM) can be explained using a shower-head analogy. A shower head receives a large amount of water through a relatively thick pipeline. It divides the water into numerous parallel streams. Each stream carries only a small amount of water, but all of the streams together together carry a large amount of water. Similarly, in an OFDM system, a large amount of data is distributed among multiple narrowband channels, with each narrowband channel carrying only a small amount of data. For example, 10 Mbps of data can be delivered to a user over 100 narrowband channels, with each channel carrying just 100 kbps.
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3 | LTE Air Interface
What is OFDMA? 900 subcarriers @ 10 kbps each = 9 Mbps
f1000 f999
f998
User 3
f102
99 subcarriers @ 10 kbps each = 990 kbps
f101 f100 eNB
User 2
f3
f2 f1
User 1
1000 10 kbps subcarriers = 10 Mbps total bandwidth available
1 subcarrier = 10 kbps
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Orthogonal Frequency Division Multiple Access (OFDMA) allows multiple users to communicate simultaneously over an OFDM radio channel. In this example, the eNB has 1000 subcarriers, each capable of carrying 10 kbps of data. The total peak rate of the eNB is therefore 1000 x 10 kbps = 10 Mbps. However, the eNB does not have to give that entire bandwidth to one user. Instead, subsets can be allocated, depending on the needs and capabilities of each user. User 1 is using a VoIP application, which only requires a single subcarrier (10 kbps). User 2 is browsing a Web site, and is assigned 99 subcarriers (990 kbps). User 3 is viewing a streaming video application and receives the remaining 900 subcarriers (9 Mbps). All of the users send and receive data at the same time, without interfering with one another. As users come and go, or as their data requirements change, the eNB can adjust their subcarrier allocations accordingly, making the maximum use of the available resources.
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3 | LTE Air Interface
Scalable OFDMA Same subcarrier spacing regardless of bandwidth
10 MHz = 1024 subcarriers
Same channel characteristics (symbol duration)
5 MHz = 512 subcarriers
Same sensitivity to time and frequency errors and multipath Award Solutions Confidential and Proprietary
Scalable OFDMA ensures that the definition of a subcarrier (its frequency spacing, symbol time, etc.) remains the same regardless of how much radio spectrum is used by the system. All that changes is the number of subcarriers available, not the subcarriers themselves. Scalability simplifies the design of OFDMA systems, by choosing a particular set of OFDM parameters that applies to all networks using that system. In this way, the subcarriers will have the same sensitivity to time, frequency errors and multipath effects, whether they are used in a 1.4 MHz system or a 20 MHz system. The signal processing requirements are therefore identical, allowing the same chipsets to be used everywhere, which reduces costs and simplifies design and development.
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47
3 | LTE Air Interface
Air Interface Features
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3 | LTE Air Interface
LTE Air Interface Features Flexibility to support different deployment scenarios • Spectrum • Bandwidth • Duplexing
Multiple-Antenna Technologies to increase coverage, capacity and throughput • Transmit Diversity for better coverage • MIMO for higher throughput and capacity • Beamforming for better coverage and capacity
Radio Access Technologies to support high-speed packet services • OFDMA in the DL for high data rate and simpler mobile design • SC-FDMA in the UL for reduced power consumption and lower PAPR
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Although all 4G systems use OFDM/OFDMA as their basic RF technology, LTE’s implementation provides a number of unique capabilities. •
Flexibility: LTE is designed to be as flexible as possible, to allow operators around the world the ability to deploy the technology in whatever spectrum they have available.
•
Radio Access Technology: Orthogonal Frequency Division Multiplexing (OFDM) can provide higher data rates and spectral efficiency over the air interface. LTE uses Orthogonal Frequency Division Multiple Access (OFDMA) in the downlink, but uses a variation of OFDMA, called Single Carrier Frequency Division Multiple Access (SC-FDMA) in the uplink to improve performance by reducing the Peak-to-Average Power Ratio (PAPR).
•
Multiple-Antenna Technology: Multiple-antenna techniques have been around for a long time, but have not yet seen wide-scale deployment. LTE will include a wide variety of advanced antenna techniques, including diversity, Single-User MIMO (SUMIMO), Multi-User MIMO (MU-MIMO), Spatial Division Multiple Access (SDMA) and beamforming.
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3 | LTE Air Interface
OFDMA in LTE
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3 | LTE Air Interface
LTE Transmission Parameters Parameters Bandwidth (MHz)
Values 1.4
3
5
Subcarrier spacing
10
15
20
15 kHz
FFT size
128
256
512
1024
1536
2048
Usable Sub-carriers
72
180
300
600
900
1200
Resource Blocks
6
15
25
50
75
100
OFDM symbols per slot
7 or 6
Modulation schemes
BPSK, QPSK (Signaling) QPSK, 16QAM, 64QAM (Data)
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Some key OFDMA/SC-FDMA transmission parameters are provided in this table. LTE is a scalable system, so the subcarrier spacing (15 kHz) is the same, regardless of the amount of spectrum. A 10 MHz system, for example, has a total of 1024 subcarriers, out of which 50 resource blocks (50*12 = 600 subcarriers) are for assignment to users.
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3 | LTE Air Interface
Generic Frame Structure Frame n-1
Frame n
Frame n+1
Frame n+2
UE
eNB
10 ms Subframe 0
Subframe 1
Subframe 2
Subframe 9
1 ms slot 0
slot 1
0.5 ms Award Solutions Confidential and Proprietary
The duration of one LTE radio frame is 10 ms. One frame is divided into 10 subframes of 1 ms each, and each subframe is divided into two slots of 0.5 ms each.
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3 | LTE Air Interface
Physical Resource Blocks slot 0
slot 1
12 Subcarriers
PRB
7 Symbols
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In LTE, radio resources are allocated in units of Physical Resource Blocks (PRBs). Normally, a PRB will contain 12 subcarriers over 7 symbols, for a total of 84 modulation symbols. If the system is configured to use the longer Cyclic Prefix in order to protect against excessive multipath, then the PRB will contain only six symbols.
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3 | LTE Air Interface
LTE Channels and Signals Broadcast Channel Paging Channel Control Channel Traffic Channel Reference Signals
UE
eNB Random Access Channel Control Channel
Traffic Channel Reference Signals
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LTE defines a number of channels and signals used to convey specific information in the uplink and downlink. •
Broadcast Channel: Contains system configuration and overhead information.
•
Paging Channel: Carries paging indications to idle mobiles.
•
Control Channel: Used by the eNB to assign resources to the UE, control uplink power, request channel quality reports, and so on.
•
Traffic Channel: Carries the actual messages and user data to the mobiles.
•
Reference Signals: Provides known signals that can be easily detected for system access and synchronization, and measured for channel estimation.
•
Random Access: Used for initial system access.
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signaling
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3 | LTE Air Interface
Multiple-Antenna Techniques in LTE
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3 | LTE Air Interface
Multiple-Antenna Benefits Reduced power consumption
Better overall signal quality
Lower interference Improved spectral efficiency
Higher capacity or throughput
Greater range or improved coverage
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Multiple-antenna techniques make optimal use of the available spectrum, improving the quality of the signal received by the UE (on the downlink) and the eNB (on the uplink). This improved radio link results in higher throughput, lower interference, lower power levels and better coverage.
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3 | LTE Air Interface
Multiple-Antenna Techniques Multiple-Antenna Techniques
Receive Diversity
Diversity Transmit Diversity Single-User MIMO (SU-MIMO)
MIMO/ Spatial Multiplexing
Multi-User MIMO (MU-MIMO) Space Division Multiple Access (SDMA)
Beamforming
Simple Beamforming (Single TX Layer SU-MIMO)
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LTE is designed to support a number of different antenna techniques to improve quality, capacity, coverage and throughput. •
Diversity: Diversity techniques exploit variations in the signals sent and received from different antennas to improve the robustness and quality of the radio link.
•
Multiple Input Multiple Output (MIMO): Also known as spatial multiplexing, MIMO techniques send different data streams over different antennas simultaneously. In SU-MIMO (Single-User MIMO), the streams are destined for the same user, increasing the net data rate. In MU-MIMO (Multi-User MIMO), the streams are intended for different users, which can be used to increase the overall capacity of the cell.
•
Beamforming: Beamforming directs the energy of the radio signal at the specific user, improving the strength and range of the signal. Spatial Division Multiple Access (SDMA) is the most complex beamforming technique, and is the theoretical foundation of MU-MIMO. Simple beamforming can be implemented as a special case of SU-MIMO, where a single transmission layer is sent on each antenna.
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3 | LTE Air Interface
Diversity
Transmit Diversity • Multiple transmit antennas • Use space and time to obtain multiple copies of the signal
Receive Diversity • Multiple receive antennas • Combine multiple copies of the signal
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The two basic forms of diversity are receive diversity and transmit diversity. In receive diversity, the receiver uses multiple antennas to retrieve different copies of the same transmitted signal. These copies are combined together to produce a better signal than would be possible with a single antenna. The odds that all copies are faded or impaired at the same time is quite low. Although receive diversity requires additional antennas and processing in the handset, the performance improvement has proven to be worth the cost. In transmit diversity, multiple copies of the same signal are sent from separate transmit antennas and are received at the other end. Again, the likelihood of all copies being poor is greatly reduced. The advantage of this approach, especially for mobile devices, is that the transmitter bears the burden of the cost of implementation.
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3 | LTE Air Interface
Single User MIMO Transmit diversity provides a robust radio path
Parallel data streams to a single user
abcd
efgh
abcd abcdefgh
abcdefgh
efgh
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Single-User MIMO (SU-MIMO) antenna techniques use multiple transmit antennas to send separate streams of data in parallel to the mobile device; the same radio frequencies and slots are used for both streams. Significant coding and processing is needed on the receiving side to extract the different streams, but the result is a significantly higher net data rate. Two transmit antennas can send twice as much data as one.
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3 | LTE Air Interface
Multi-User MIMO/SDMA Users reuse the same radio resources (frequencies and slots)
Parallel data streams to multiple users
abcd abcd
1234
1234
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Multiple-User MIMO (MU-MIMO) systems (also known as Space Division Multiple Access, or SDMA) allow multiple users separated in space to use the same frequencies and slots simultaneously. Each user, in effect, has access to all of the cell’s resources independently of what the other users are doing, resulting in a significant increase in spectral efficiency and system capacity. However, MUMIMO/SDMA systems are extremely complex and costly to implement, especially on mobile devices.
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3 | LTE Air Interface
Summary • Orthogonal Frequency Division Multiplexing (OFDM) is the fundamental radio technology in all 4G systems. It has: – Very high spectral efficiency, – Scalable bandwidth, and – Support for multiple-antenna techniques.
• The LTE air interface is designed for flexibility in: – Spectrum, – Bandwidth, and – Duplexing schemes.
• LTE supports a wide variety of antenna techniques to improve performance, including: – – – –
Diversity, Single-User MIMO, Multiple-User MIMO, Beamforming. Award Solutions Confidential and Proprietary
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3 | LTE Air Interface
Review Questions 1. What does it mean to be orthogonal in a radio channel? 2. What is the value of being flexible in: –
Spectrum
–
Bandwidth
3. What is the maximum number of data subcarriers available in LTE? 4. What are the benefits of multiple-antenna techniques? What are the drawbacks?
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4 | LTE Services
Chapter 4: LTE Services
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4 | LTE Services
Objectives After completing this module, you will be able to: •
Illustrate the trends in wireless services
•
Identify the drivers behind 4G technologies
•
List the QoS classes supported in LTE
•
Identify the security features provided in LTE
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4 | LTE Services
Drivers of 4G Services
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4 | LTE Services
Services Evolution 1980’s
Voice
1990’s
2000’s
Voice + low-speed data (e.g., SMS)
Voice + high-speed data (Internet, video, gaming, etc.)
2010+
?
Data Revenue
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presenting combined requirements for predictable throughput, latency and jitter.
The diagram depicts the direction of wireless services from the following perspectives: •
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Applications: Initial wireless systems provided voicecentric services, such as the ability to make and receive phone calls. After a while, voice and lowspeed data services became popular. For example, Short Message Service (SMS) is a low-speed data service where just a few bytes of data are transferred over the air. Emerging wireless applications now include a wide variety of services, many of which require high data rates over the air. For instance, when a user downloads a streaming video, a news clip or a movie, only a high-speed radio connection results in a satisfying user experience. Low data rates are inadequate for a satisfying quality of experience in such scenarios. Another important consideration is maintaining the ability to handle voice communications. In IP-based wireless systems, voice is no longer carried in a circuit. It is transported in an IP packet using Voice over IP (VoIP). This necessitates strict performance control. To summarize, contemporary applications are multimedia in nature,
•
Revenue: Voice is still the king - the dominant application. Voice continues to generate most of the revenue for a wireless service provider. However, revenue growth from voice is quite low due to increased competition and declining price-perminute. On the other hand, revenue growth from data is very strong and becomes a new growth point.
Based on these two perspectives, the need for a wireless system that can support a wide range of services is apparent.
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4 | LTE Services
Drivers of 4G Networks Services Enable
Quad-play (voice, video, data, mobility)
Increased usage at lower prices
Infrastructure Vendors High-speed 4G networks
Drive
Users
Encourage
Chipset and Device Vendors Increasing device capabilities
Network Operators Demand
Higher capacity, lower CAPEX/OPEX
Challenge
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This slide shows the drivers of 4G networks - better user experiences and low cost. With the advance of DSP technology, device processing capabilities become more and more powerful, which can support high-speed, real-time applications, such as 3D multi-player online games, and high-resolution online movies. At the same time, users are getting used to mobile content anywhere, anytime, and wish to have the same experience with fixed high-speed Internet. The increasing amount of mobile usage is welcomed by wireless operators, but also brings challenges to the operators’ profitability. Users are expecting much better services for the same price. Operators need to increase network capacity and/or throughput to support higherspeed traffic and lower costs at the same time. The solution to improve user experience and lower cost is evolving the current 3G systems into 4G networks. The building blocks of a 4G network include OFDM, multipleantenna techniques, all-IP architecture and the IMS.
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4 | LTE Services
Services in LTE
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4 | LTE Services
QoS Classes in LTE QCI
Priority
Application
Guaranteed Bit Rate
Packet Delay
Packet Loss
5
1
IMS signaling
No
100 ms
10-6
1
2
Conversational VoIP
Yes
100 ms
10-2
3
3
Real-time gaming
Yes
50 ms
10-3
2
4
Conversational video (live streaming)
Yes
150 ms
10-3
4
5
Non-conversational video (buffered)
Yes
300 ms
10-6
6
6
Video (buffered)
No
300 ms
10-6
7
7
Voice, video, interactive games
No
100 ms
10-3
8
8
TCP applications (Web, e-mail, FTP)
No
300 ms
10-6
9
9
Platinum vs. gold users
No
300 ms
10-6
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LTE defines nine Quality of Service (QoS) classes, each associated with a priority, specific delay, and packet-loss values, and whether the service has a guaranteed bit rate. These characteristics will be used by the Evolved Packet System (EPS) nodes (the eNB, S-GW, and P-GW) as a guide in deciding how a particular service data flow is to be processed.
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4 | LTE Services
Better User Experience with LTE Large-scale streaming, downloading and sharing of video, music and rich multimedia content Example Services Rich voice
Current support Real-time audio
LTE support VoIP, high quality video conferencing, video calls
Web browsing Access to online services
Super-fast browsing / uploading
Messaging
SMS, MMS
Photo messaging, video messaging
Games
Downloadable and online games
Consistent online gaming experience across both fixed and mobile networks
TV/video on demand
Streamed and downloadable Broadcast television services, true video content on-demand television, high quality video streaming
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Although many services are available in 3G networks, LTE will provide a better user experience, and thus push data usage in the mobile environment. For example, access to online services is available in 3G networks now, but LTE will support super-fast browsing and uploading, and give users the same experience as in the fixed network. The same mobile and fixed experience enables the ultimate seamless mobility. Reference: “Toward Global Mobile Broadband,” UMTS Forum, February 2008.
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4 | LTE Services
How Will LTE Deliver? Low latency • 5 ms: User plane RAN
High data rates at high mobility • DL: > 100 Mbps • UL: > 50 Mbps
• 100 ms: control plane dormant to active transmission
Characteristics of LTE Guaranteed QoS Low cost • All-IP
• Wide coverage • Security
• OFDM + multiple antenna solutions • Spectrum scalability
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LTE is one of the candidates capable of delivering a variety of delay-sensitive and bandwidth-intensive services. The main strengths of LTE are (a) a high data rate and high-capacity network, (b) low latency, (c) low cost, (d) QoS guarantees, and (e) wide coverage and security. •
High Data Rate and High-Capacity Network: LTE is designed to support a high data rate at high mobility and high capacity. In the 20 MHz bandwidth, the DL data rate is more than 100 Mbps and the UL data rate is more than 50 Mbps. The advanced technology in air interface and higher capacity in backhaul enables high capacity for LTE.
•
Low Latency: Low latency enables the better support for real-time applications.
•
Low Cost: New air interface technology enables high spectral efficiency. All-IP based, flat network architecture enables simplicity and scalability, and thus lowers the cost for operators. The machine-tomachine application will bring the terminal scalability up while lowering the cost for users.
•
Enhanced QoS: Enhanced QoS will enable operators to differentiate services and support more business models. Enhanced QoS also enables users who are willing to pay more to get premium services.
•
Wide Coverage and Security: These are other characteristics contributing to the competency of LTE.
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4 | LTE Services
Security in LTE
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4 | LTE Services
LTE Security Features User Identity and device confidentiality
Mutual Authentication and key agreement
LTE Security Encryption
Integrity
Network Domain Security
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When we talk about security in LTE networks, we limit ourselves to the protection of LTE network resources and the protection of user identity and information. Protection in this case means protection against unauthorized access to the system, protection against snooping, and manipulation of data. In LTE, this relates to the following security services: •
Encryption is the property of communicating such that the intended recipient knows what is being sent, but unauthorized parties do not. This service takes care of the threat of an eavesdropper snooping for critical data. Anonymity is a subset of this, and conceals the origin and destination of a piece of information while in transit. Anonymity takes care of the threat of eavesdropping used to analyze traffic patterns for unauthorized uses.
•
Authentication is the property of knowing that the sender of data is indeed the person he says he is. When a user first starts a session with an Internet server, he must first log in. It is important at this critical time that the user and the server authenticate each other. In addition, for an ongoing session, the
sender and receiver might need to authenticate each other for every message to protect themselves against a “man-in-the-middle” attack. Authentication takes care of the threat of impersonation.
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4 | LTE Services
LTE Security Features (continued) User Identity and device confidentiality
Mutual Authentication and key agreement
LTE Security Encryption
Integrity
Network Domain Security
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•
•
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Integrity Checking is a service that ensures that data in transit from a source to a destination cannot be altered without detection. Integrity of the message can be checked by sending a checksum of the message and comparing it with a recalculated checksum at the receiving end. Integrity checking guards against the threat of man-in-the-middle attacks. An integrity service can also guard against message replay by including a sequence number in the message. Then, if the message is replayed at a later time, the receiver will detect that it is stale – this is often referred to as replay protection.
(Globally Unique Temporary Identity) , etc. •
Network Domain Security ensures security over the wireline connection between any two nodes like the eNB and the MME. This includes authentication, encryption and integrity protection.
User Identity and Device Confidentiality ensures that the user identity (IMSI) and equipment identity are not accessible to unauthorized people. Unauthorized access to the IMSI or IMEI may help track the movement of a UE, services used by the UE and the country that the user belongs to. The IMEI is always transmitted over the air after enabling encryption. The IMSI is very rarely used in a message. Instead, every UE is identified by temporary identities like the C-RNTI (Cell-Radio Network Temporary Identity), GUTI
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4 | LTE Services
Summary • 4G networks are designed to enable advanced packet-oriented services, which in turn drive customer usage and operator revenues. • LTE provides a better user experience by improving or enabling: – Spectrally efficient Voice over IP (VoIP), and – Large-scale streaming/downloading/sharing of high quality music/video/multimedia content.
• LTE security mechanisms protect network resources, confirm user identities, and validate signaling messages. Award Solutions Confidential and Proprietary
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4 | LTE Services
Review Questions 1. What will be the ‘killer app’ for LTE networks? 2. How are the defined QoS classes used to improve service quality? 3. What security mechanism ensures privacy of signaling messages and user data?
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5 | Life of an LTE Mobile
Chapter 5:
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5 | Life of an LTE Mobile
Objectives After completing this module, you will be able to: • • •
Step through the end-to-end call setup in LTE List and describe the steps of downlink and uplink data transmission Identify and describe the three steps of the handover procedure in LTE
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References: [1]
3GPP TS 36.300; (E-UTRA) and (E-UTRAN); Overall description; Stage 2 (Release 8)
[2]
3GPP TS 36.211; Physical Channels and Modulation (Release 8)
[3]
3GPP TS 36.212; Multiplexing and channel coding (Release 8)
[4]
3GPP TS 36.213; (Release 8)
[5]
3GPP TS 23.401; General Packet Radio Service (GPRS) enhancements for Evolved Universal Terrestrial Radio Access Network (E-UTRAN) access
[6]
3GPP TS 23.402; Architecture Enhancements for non-3GPP accesses (Release 8)
[7]
3GPP TR 23.882; Report on Technical Options and Conclusions (Release 7)
[8]
3GPP TR 25.814; Physical layer aspects for evolved Universal Terrestrial Radio Access (UTRA) (Release 7)
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Physical
layer
procedures
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5 | Life of an LTE Mobile
LTE Call Setup
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5 | Life of an LTE Mobile
LTE Connection Setup 1
UE acquires Network
E-UTRAN helps with acquisition
2
UE gets Signaling Connection
E-UTRAN recognizes UE
3
UE requests Attach
EPC accepts request for Attach
4
UE is Authenticated
EPC authenticates UE
5
UE gets IP Connectivity
EPC assigns an IP address
6
UE requests a Service
EPC grants Service with QoS
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Let’s examine the operation of a UE from power-up until it is in traffic state with the network. The following list illustrates the various operations of the UE. •
•
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UE Acquires Network: When the UE first powers up, it enters into a cell search procedure. Cell search is a method by which the UE acquires frequency and timing synchronization with the cell and detects the cell ID. The cell search procedure is accomplished using synchronization signals followed by cell identification. With the physical layer cell ID determined, the UE is synchronized with the eNodeB in the downlink, and is ready to acquire system broadcast information. Next, the UE listens to the broadcast channel to decode broadcast system information such as the frequency of operation of the traffic channels, PLMN identities, tracking area identity, and so on.
•
UE Requests Attach: The UE now uses the established signaling connection to connect and register with the EPC. This evokes certain reactions from the EPC like authentication, assignment of an IP address, granting of a basic bearer path to initiate services, etc.
•
UE is Authenticated: The EPC now goes through authentication, authorization and security procedures for the UE by communicating with the HSS and the AuC. This validates the UE and ensures only valid subscribers are allowed onto the LTE network.
UE Gets Signaling Connection: The first step in ANY messaging or service is the establishment of a Radio Resource Control (RRC) signaling connection with the E-UTRAN.
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5 | Life of an LTE Mobile
LTE Connection Setup (continued) 1
UE acquires Network
E-UTRAN helps with acquisition
2
UE gets Signaling Connection
E-UTRAN recognizes UE
3
UE requests Attach
EPC accepts request for Attach
4
UE is Authenticated
EPC authenticates UE
5
UE gets IP Connectivity
EPC assigns an IP address
6
UE requests a Service
EPC grants Service with QoS
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•
UE Gets IP Connectivity: Once the authentication and authorization procedure is complete, the UE is assigned an IP address and a default bearer path. The UE can initiate packet data services using this IP address (e.g., email).
•
UE Requests a Service: At this point, the UE has an RF connection and an IP address. However, it has not initiated any service such as VoIP or Internet access. The UE communicates with the eNB to establish a service. With the default bearer path, the UE can request packet services needing high data rates and a subscribed QoS. Depending on the requested QoS, the network can assign resources both on the radio interface and on the core network. Now, any additional bearer paths are set up through which the UE can transmit or receive information packets.
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5 | Life of an LTE Mobile
Step 1: The UE Acquires the Network Q1: Where am I? A1: Look for a channel based on preferred roaming list and get the ID of the eNB
eNB Q4: Do I know what the network is capable of? A4: Yes … it is an FDD network with 10 MHz wide carrier … and I know its rules …
UE
Q3: Which network? A3: Read the network broadcast information
Q2: How is the network sending me information? A2: Synchronize with the network and acquire timing
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After power-on, the UE looks for an LTE network on the radio channel that is pre-programmed into the UE via a mechanism such as a preferred roaming list in its USIM card. Regardless of the bandwidth option, it acquires the center frequency of the spectrum. Once it acquires the center frequency, it extracts timing information (symbol, slot, sub-frame and frame).
The UE may search each carrier in turn (“initial cell selection”) or make use of stored information to shorten the search (“stored information cell selection”).
The LTE E-UTRAN system provides two physical signals: the primary synchronization signal and the secondary synchronization signal. The role of these two signals is to help the UE acquire timing synchronization and identification of a physical layer cell ID. With time synchronization, the UE now knows the physical layer cell identity. With the physical layer cell ID determined, the UE is synchronized with the eNB in the downlink and is ready to hear the system information broadcast by each eNB on the broadcast channel to gain access to services. The UE reads broadcasted cell system information to identify its PLMN(s). It identifies a selected PLMN and equivalent PLMNs by initially searching the E-UTRA frequency bands. For each frequency band, it identifies the strongest cell.
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5 | Life of an LTE Mobile
Step 2: UE Gets Signaling Connection Step 3: UE Sends Attach Request Here is your temporary ID, use this for now.
Can we establish a signaling connection?
Step 2 Setup a Signaling Connection eNB
Here is your temporary ID
UE
Step 3
Attach Request
I would like to attach to the network. Please, pass this request to the EPC network.
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The first step in any messaging or service is the establishment of an RRC connection. This is needed to invoke a service. In this flow, the UE requests an RRC connection to perform registration. With the establishment of the RRC connection, the UE and eNB recognize each other, and the eNB provides the UE with radio-network-specific identifiers. Now that they have a signaling path with each other, they can exchange any kind of messaging. This allows the UE to send an Attach request to the eNB to route to the EPC network so it can start the process of getting authenticated and eventually get an IP address to start service initiation.
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5 | Life of an LTE Mobile
Step 4: UE Gets Authenticated HSS/ AuC
Who are you? This is me…
Who are you? This is me…
Step 4 Mutual Authentication EPC
UE
eNB
or
Mutual Authentication Key Exchange
Make sure the network and UE are valid Prepare for encryption
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The MME, on receiving the Attach request from the UE, will initiate authentication-related procedures. The MME registers itself in the HSS as serving the UE. The HSS confirms the registration of the new MME. Subscription data authorizing the default IP access bearer is transferred. Information for policy and charging control of the default IP access bearer is sent to the MME. The MME and the UE go through authentication and authorization procedures based on information provided to the MME from the HSS/AuC. Only a successful mutual authentication will allow the progress of the connection to the next stage.
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5 | Life of an LTE Mobile
Step 5: UE Gets IP Connectivity Step 5 IP Connectivity
EPC
Default Bearer Path
UE
eNB Default Access Bearer
Default Radio Bearer
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The IP (IPv4) address is allocated during the default bearer activation. The P-GW configures the IP layer with the user’s IP address. The user plane is established and the default policy and charging rules are applied. The MME/S-GW provides the evolved RAN with QoS configurations for the default IP access bearer (e.g., the upper limits for transmission data rates). LTE supports IPv4, IPv6 and dual-stack IP (DSMIPv6) addressing for a single bearer path.
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5 | Life of an LTE Mobile
Step 6: UE Requests a Service Evaluate QoS against available resources Service negotiation on signaling connection
EPC
UE eNB Radio Bearer with QoS
Access Bearer with QoS
All steps … Done! Use the system to get services…
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Once the default bearer path is established, if the user wants to initiate a new service with a higher QoS, the user can request resources. These resources can set up bearers with different QoS according to the service requested. The following is a high-level flow: 1.
The UE has a signaling relation established with the network that uses the default IP access bearer.
2.
The MME/S-GW is triggered by a resource request that contains policy/QoS information corresponding to the requested service from the P-GW.
3.
The MME/S-GW checks the UE's subscription, performs admission control according to the received QoS information and available resources, and applies the received policy information.
4.
The MME/S-GW initiates the resource establishment toward the responsible LTE-RAN functions.
5.
The responsible LTE-RAN functions perform admission control. Translation of the received QoS information into radio QoS information is performed. The allocation of radio resources and the appropriate
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configuration of the scheduler are performed according to the translated QoS information. 6.
The UE is provided with information about the radio configuration necessary for the service and related information to link radio resources with IP or session flows.
7.
The MME/S-GW is informed about the successful outcome of the resource establishment.
8.
The MME reports the outcome of the resource establishment together with the negotiated QoS.
So, a new radio bearer and access bearer are established with a new QoS, and DL and UL data transmissions can commence.
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5 | Life of an LTE Mobile
Traffic Operations
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5 | Life of an LTE Mobile
Downlink Traffic Operations Channel Quality Indicator 1 UE 1
Channel Quality Indicator UE 2
eNB
Control Information
2 3
Data Transmission 4
Scheduler
Ack/Nack
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In LTE, all downlink traffic flows over the Physical Downlink Shared Channel (PDSCH). As the name implies, the channel is shared by multiple UEs. In order to maximize the effectiveness of the PDSCH, a basic 4-step process is used: 1.
Each UE assigned to the PDSCH reports a Channel Quality Indicator (CQI) to the eNB, reflecting the UE’s estimated current radio channel conditions on the downlink. The eNB stores the CQI reports from all of the UEs and uses the information to determine its next step.
2.
The eNB runs an internal scheduler algorithm to decide which UE’s data should be transmitted next, based on its last reported CQI and other factors.
3.
The CQI value for the selected user helps determine the coding and modulation scheme, the amount of radio resources and the data rate to be used for the transmission. The user’s data is sent over the PDSCH, and, in parallel, related control information is sent over the Physical Downlink Control Channel (PDCCH) to inform the UE when to expect the data and how to
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decode it. 4.
The UE receives the data and verifies the checksum. If the transmission was received properly, the UE transmits an ACK to the eNB, indicating that the transmission can stop. However, if there are errors, the UE sends a NACK to request additional information to resolve the errors.
This cycle is repeated continuously for as long as there is data to be sent over the PDSCH.
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5 | Life of an LTE Mobile
Uplink Traffic Operation 1
Scheduling Request Scheduling Grant
UE
2
3
Buffer Status Report Scheduling Grants 5
eNodeB 4
2 4
Scheduler
Data Transmissions 6
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This slide provides a high-level picture of a typical eNBcontrolled scheduled-mode UL-SCH operation. When a UE first attaches to a network and has date to send, it needs to tell the eNB.
1.
2.
The PUCCH is allocated on one resource block in each of the slots in a subframe. The number of resource blocks in a slot used for transmission of the PUCCH is set by higher layers. If the UE has something to send. It needs to indicate this to the eNB via a scheduling request. The scheduler at the eNB responds with a UL scheduling grant.
Once a UE has been assigned a UL-SCH for uplink data transmission, the UE follows the following steps: 3.
The UE looks at its buffer status for each channel and sends a Buffer Status Report serving cell. The information includes the channel identity, buffer status and available ratio at the UE.
4.
The scheduler algorithm is executed at the eNB. The serving UL-SCH cell typically provides a power allocation or scheduling grant to the UE.
5.
The UE transmits the data on the UL-SCH/PUSCH channels.
6.
The serving cell makes a determination of the ACK or NACK to be sent on the PDCCH in response to the received data on the PUSCH. The PDCCH signals the HARQ process number, and if it is a transmission or retransmission. Retransmissions are always scheduled through the PDCCH.
This sequence is repeated for every Transmit Time Interval (TTI) cycle as needed. Note that Steps 1 and 2 may not be required for each TTI transmission.
logical to the logical power
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5 | Life of an LTE Mobile
Handovers
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5 | Life of an LTE Mobile
Now, the UE Moves…No Problem! 1. Initial communication with eNB 1
eNB 3
2. Connection with eNB 1 broken
• Break before make • Hard handover • No soft handover in LTE
3. Connection with eNB 2 established eNB 1
1
3
2
eNB 2
UE Movement
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The figure shows a break-before-make handover. Initially, the UE communicates with the serving eNB, eNB 1. The UE continues to monitor signals from the eNBs in its neighborhood (called neighbors). There are three neighbors: eNB 2, eNB 3, and eNB 4. As the UE moves away from eNB 1, and toward a neighbor eNB 2, it finds eNB 2 to be a better eNB 1. Now, eNB 2 becomes the target eNB for a handover. The communication link between the currently serving eNB, eNB 1, and the UE is broken, and a new link between the UE and the target eNB, eNB 2, is established at the end of the handover. Since the new link is established after the previous link is broken, this type of handover is called a break-beforemake handover.
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5 | Life of an LTE Mobile
Handover Preparation Ongoing call
EPS Radio Bearer 1. Measurement Report
UE
X2 3. GTP tunnel is established
EPS Access Bearer
MME/ S-GW
2. Handover Decision Source to target eNB
eNB
4. Assignment of resources by Target eNB
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Let’s look at the procedure of the Intra-MME Hard Handover, which is executed in three phases: 1.
Handover Preparation Phase: During this phase, tunnels are established between the source eNB and the target eNB.
2.
Handover Execution Phase: During this phase, user data packets are forwarded from the source eNB to the target eNB until the source eNB buffer is empty.
3.
Handover Completion Phase: During this phase, the target eNB initiates a Path Switch procedure to establish an EPS bearer between the target eNB and the S-GW for data. The source eNB continues to forward data to the target eNB.
established EPS bearer. Also, the source eNB receives the periodic measurement reports. Based on the measurement reporting, the source eNB decides to perform a HO. When the source eNB decides to handover the UE to the target eNB, the source eNB first establishes an X2-interface GTP tunnel between itself and the target eNB. During this phase, the target eNB assigns the required radio resources to the UE.
During the handover preparation phase, the UE takes measurements of its surrounding environment as instructed by the E-UTRAN. Based on the requirement set by the E-UTRAN, the UE may need to send a measurement report to inform the E-UTRAN for handover consideration. The call is carried on with the source eNB and serving SGW/P-GW. The data packets are carried through the
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5 | Life of an LTE Mobile
Handover Execution Ongoing call
EPS Radio Bearer UE
EPS Access Bearer
MME/ S-GW
Source eNB
X2
5. Establish EPS radio bearer from target eNB
6. Data forwarding
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With the completion of the handover preparation phase, the handover execution phase starts. Two critical procedures are performed during this phase: 1.
The source eNB buffer containing unacknowledged data is forwarded to the buffer at the target eNB. The new user packets from the S-GW can still be forwarded through the source eNB during this stage.
2.
An EPS radio bearer is established between the UE and the target eNB based on radio resources assigned to the UE.
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5 | Life of an LTE Mobile
Handover Completion 6. Release Data Forwarding 9. EPS bearers
X
EPS Radio Bearer
MME/ S- GW
Source eNB
X2 8. Receive Data from target eNB
X
EPS Access Bearer
X
7. Establish EPS access bearer to Target eNB
EPS Radio Bearer UE
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Finally, the handover completion phase starts with the establishment of an EPS radio bearer with the target eNB (completion of the handover execution phase). This phase involves a path switching procedure. In this process, a new EPS access bearer from the target eNB to the S-GW is first established, and then mapped to the existing EPS radio bearer. Now, the user data packets from the S-GW are forwarded to the UE through the EPS access bearer toward the target eNB and the new EPS radio bearer. The EPS radio and access bearers from the old source eNB EPS bearer and the X2-interface GTP-U tunnel between two eNBs are released.
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5 | Life of an LTE Mobile
Summary • The steps of an end-to-end LTE call setup include: – – – – – –
Acquiring the network, Requesting a signaling connection, Attaching to the network, Authenticating the UE, Getting IP connectivity, and Requesting a service.
• The eNB owns and allocates all radio resources. – UEs monitor the control channel to see if they are about to receive data on the downlink. – UEs must explicitly request resources to transmit data on the uplink.
• All handovers are hard handovers controlled by the eNBs. Award Solutions Confidential and Proprietary
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Review Questions 1. What is the purpose of mutual authentication? 2. When does the UE get its IP address? 3. How does the UE know when and where to look for its data on the downlink? 4. List the key steps of LTE handover 5. Which node makes the decision to hand over?
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6 | LTE Deployment
Chapter 6: LTE Deployment
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6 | LTE Deployment
Objectives After completing this module, you will be able to: • • •
Describe the different LTE UE categories Identify the planning considerations associated with deploying LTE Predict theoretical LTE performance
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References: [1]
3GPP TS 23.402; Architecture Enhancements for non-3GPP accesses
[2]
3GPP TS 23.401; GPRS enhancements for LTE access
[3]
3GPP TS 36.300; Evolved Universal Terrestrial Radio Access (E-UTRA) and Evolved Universal Terrestrial Radio Access Network (E-UTRAN)
[4]
3GPP TR 23.882; 3GPP System Architecture Evolution
[5]
3GPP TS 36.306; Evolved Universal Terrestrial Radio Access (E-UTRA) User Equipment (UE) radio access capabilities
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6 | LTE Deployment
Device Capabilities
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6 | LTE Deployment
LTE Device Capabilities Category Bandwidth
MIMO
Duplexing
MHz
Modulation UL
DL
1 2 3 4 5
1.4, 3, 5, 10, 15, 20
Up to 2x2*
FDD, H-FDD, TDD
Up to 4x4*
QPSK, 16QAM QPSK, 16QAM, 64QAM
QPSK, 16QAM, 64QAM
Data Rates (Mbps) UL
DL
5
10
25
51
51
100
51
150
75
300
Note: Multiple transmit antennas are supported on the downlink only.
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Five different categories of LTE devices have been defined, similar to HSDPA and HSUPA categories for UMTS devices. The categories define some of the basic physical capabilities of the UE. The categories differ primarily in the peak data rate that each supports, ranging from 5 Mbps on the uplink and 10 Mbps on the downlink for a Category 1 device, to 75 Mbps on the uplink and 300 Mbps on the downlink for a Category 5 device. Currently, all LTE categories support the same values for system bandwidth, MIMO support and duplexing schemes, although these are still subject to change. Note that support for multiple transmit antennas only applies to the downlink, and that only a Category 5 LTE UE supports 64QAM modulation on the uplink.
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6 | LTE Deployment
Planning for LTE
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6 | LTE Deployment
Frequency Planning Same frequency/subcarriers
1 3
Partial frequency/subcarriers in cell edge
2
– Frequency reuse of 1/3 – Less interference – Simple radio resource allocation – Lower spectral efficiency
– Fractional frequency reuse – eNBs coordinate subcarrier allocation at cell edge to minimize interference – Higher interference – Complex radio resource allocation – Higher spectral efficiency
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Frequency planning is an important part of wireless network planning. In a GSM network, the frequency planning is complex, and is the key to network performance. In networks using CDMA technology, the frequency reuse is 1 and the frequency planning is simple. In OFDM-based systems such as LTE, frequency planning is more complex. In LTE, the entire system bandwidth is divided into many subcarriers, and a channel consists of many subcarriers. With a cell, the subcarriers for MS1 are different from the subcarriers for MS2. This is called frequency diversity. In the cell edge, MS1 in cell 1 and MS2 in cell2 may have some common subcarriers, but not all. By coordination between the neighboring BSs, the interference can be lowered. This is called interference diversity.
neighboring cells and no coordination between BSs is needed. The drawback is lower spectral efficiency. The second option is fractional frequency reuse, where the same frequency/subcarriers are used within the cell and partial frequency/subcarriers are used in the cell edge. The frequency reuse factor is a little bit less than 1. For example, the same 5 MHz bandwidth can be used on all three sectors of a site. At the cell edge, the BSs coordinate subcarrier allocation to minimize interference. The benefit of this option is higher spectral efficiency. The drawback is higher interference and complex radio resource allocation.
There are two options for frequency planning in LTE. First, three sectors of a site use different frequency bands. The frequency reuse factor is 1/3. For example, if the system is deploying using a 5 MHz bandwidth, a 15 MHz (5X3) bandwidth will be needed. The benefits of this option is less interference and simple radio resource allocation. Different frequencies are used at the cell edge of two
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6 | LTE Deployment
Multiple-Antenna Planning Adaptive switching based on radio condition (share the same set of physical antennas)
Multiple-Antenna Mode Selection Techniques
Benefits
Transmit diversity
Increase cell coverage
SU-MIMO
Increase user throughput/cell throughput
MU-MIMO (SDMA)
Increase number of users/cell capacity and throughput
Beamforming
Increase cell edge performance
Transmit diversity
MIMO
Multiple Antenna Configuration
Beamforming
Number of antennas
Tradeoff between performance and cost, tower top space
Number of cables
Electronics on top (one cable totally) or on ground (one cable per antenna)
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Multiple antennas are mandatory in LTE deployment and LTE supports different multiple-antenna techniques and different antenna configurations. Different multiple-antenna techniques provide different benefits. Transmit diversity increases cell coverage, SUMIMO increases user throughput and cell throughput, MUMIMO increases cell capacity and cell throughput, and beamforming increases cell edge performance. Since different techniques bring benefits to different scenarios, it will be a good solution to adaptively switch techniques based on radio conditions. For example, when an MS moves near the BS, use MIMO; when an MS locates at the cell edge, use transmit diversity or beamforming. Transmit diversity is open-loop and simple to implement, while beamforming needs feedback on channel conditions and is complex but with better performance. Note that all the techniques can share the same physical antennas on the tower top.
transmitter and receiver electronics are. If the electronics go to the tower-top, only one cable is needed; if the electronics are located on the ground, multiple cables are needed, one cable for each antenna.
Another thing to decide is how many antennas should be used. This is a trade-off between performance and cost. Also, tower-top space is a factor. The number of cables from the tower-top to the ground depends on where the
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6 | LTE Deployment
4G Backhaul Challenges Air Interface Data Rates in 2G/3G/4G Networks
2G 3G 4G
Technology
Theoretical Peak Rate
Practical Data Rate
GSM
56 kbps
14.4 kbps
IS-95
115.2 kbps
14.4 kbps
UMTS/HSPA
14 Mbps
400~700 kbps
1x EV-DO
3 Mbps
400~800 kbps
WiMAX
75-300 Mbps
10 Mbps in DL 2-3 Mbps in UL
LTE
300 Mbps
TBD
2G/3G
4G
Air Interface
Air Interface
T1/E1 works
T1/E1 does not work anymore
Backhaul
Backhaul
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The fast growing wireless data service demands more bandwidth and higher data rates. This brings in the 4G networks, which increases air-interface throughput significantly by using OFDM and multiple-antenna techniques. At the same time, backhaul capacity becomes the bottleneck of the network. A backhaul solution is critical to improved network performance and cost. The table lists air-interface data rates in 2G, 3G and 4G networks. For 2G/3G networks, the practical data rate is 10s or 100s of kbps, one or several T1/E1 can support the backhaul traffic. But for 4G, the theoretical peak data rate goes up to 300 Mbps. The practical data rate would be lower, but the traditional T1/E1 is no longer able to support the requirement with reasonable cost.
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6 | LTE Deployment
Backhaul Alternatives T-1
1.544 Mbps
150 Mbps ~ 100 T-1 capacity
OC-3
600 Mbps OC-12
~ 400 T-1 capacity 1 Gbps
GigE
~ 600+ T1 capacity ~ 50-100 T1 capacity
Microwave
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Today, in the United States, the vast majority of wireless backhaul is T1-based. This is largely due to the natural evolution of wireless networks and the nature and volume of traffic that they support. Commercially available alternatives to T1 service are principally fiber-based. Microwave radio is also a viable alternative for some operator and some cell sites. However, as you might expect, the monthly tariff is much higher for 150 Mbps capacity than it is for 1.5 Mbps. At the same time, fiberbased services are available that charge for “capacity that is used.” In other words, while availability varies by market, if a cell site is served by an OC3 and the cell only requires 20 Mbps of capacity, that is all that the wireless operator pays for. This produces a profitable business model for both the Local Exchange Carrier (LEC) or fiber provider and the wireless service provider.
capacity is mushrooming. Consider the aggregation network capacity required to give every home 50 Mbps of narrowcast bandwidth. It rapidly turns into terabits in the distribution and core network. The aggressive roll-out of FTTH and FTTP is marching fiber within the proximity of most urban and suburban cell sites.
Gigabit Ethernet networks are being deployed in many metropolitan markets and are being used to support the ever-expanding requirement for increased capacity at the edge of the network, i.e., as homes and business are evolving to Fiber to the Home (FTTH) and Fiber to The Premise (FTTP)-based access, aggregation network
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6 | LTE Deployment
LTE Performance - VoIP Capacity LTE VoIP Capacity Estimate Deployment Scenario
Average VoIP Capacity (users/sector) DL
UL
Case 1
317
241
Case 3
289
123
Assume: (a). VoIP traffic model = Full rate AMR with 50 percent VAF (b). Outage = 95 percent coverage for 2 percent FER at 50 ms air interface delay bound (c). System bandwidth = 5MHz 350
317 289
300
-
241
250 200
Case 1 150
123
Case 3
100 50
Assume a homogenous user distribution - Case 1: inter-site distance = 500 m - Case 3: inter-site distance = 1732 m
0 DL
UL
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Source: www.3GPP.org
Voice capacity (the number of simultaneous calls that can be supported on a radio channel) can be difficult to estimate, especially with packet-based (VoIP) calls on a shared channel; the impact of changing radio conditions and of other services running on the same channel can be significant. Nonetheless, it’s important to get a feel of how LTE compares to other technologies when it comes time to handling voice. This chart summarizes a simulation study by 3GPP on LTE VoIP performance on a 5 MHz channel (comparable to a single UMTS radio channel). Under a variety of assumptions and conditions, the estimated voice capacity of the channel ranged between 123 and 241 users. By way of comparison, a typical UMTS channel may handle between 60 and 80 users; even with the overheads associated with packetized voice, LTE is significantly more efficient than UMTS. Reference: 3GPP TSG-RAN WG1 #49 - R1-072570: Performance Evaluation Checkpoint: VoIP Summary.
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6 | LTE Deployment
Summary • Device categories identify the physical characteristics of the UE, including peak data rates and MIMO support. • LTE network deployment considerations include: – Spectrum and bandwidth, – Use of multiple antennas, and – Backhaul capacity.
• The simulated LTE performance meets or exceeds the LTE targets.
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6 | LTE Deployment
Review Questions 1. Why does LTE define multiple UE categories? 2. What are the key challenges with deploying multiple-antenna solutions? 3. Why is backhaul capacity an important deployment consideration?
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A | Additional Topics
Appendix A: Additional Topics
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A | Additional Topics
Objectives After completing this module, you will be able to: • Compare features and capabilities of LTE and WiMAX • Step through the interworking of LTE with: • 3GPP (UMTS/HSPA and GSM/GPRS), and • 3GPP2 (1xEV-DO)
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A | Additional Topics
LTE and WiMAX: Similarities and Differences Award Solutions Confidential and Proprietary
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A | Additional Topics
LTE vs. WiMAX: Similarity
VoIP and High-Speed Data Applications
OFDM
Multiple-Antenna Techniques
All-IP Architecture
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This slide shows the similarities between LTE and WIMAX. Both are 4G technologies able to support VoIP and highspeed data applications. The targeted data rate will be in 100s of Mbps and latency will be less than 10 ms. Both LTE and WiMAX are based on the same foundation: OFDM, multiple-antenna techniques, and all-IP architecture. These similarities make network convergence and seamless mobility easier.
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A | Additional Topics
LTE vs. WiMAX: Key Market Differences LTE
Mobile WiMAX
Genesis
3GPP
IEEE + WiMAX Forum
Spectrum
Initial deployment in FDD spectrum
Initial deployment in TDD mode in 2.3, 2.5 and 3.5 GHz
Time of Deployment
Approximately 2010
2007 and beyond
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This table lists the market differences between LTE and WiMAX.
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A | Additional Topics
LTE vs. WiMAX: Key Technical Differences LTE
Mobile WiMAX
Comments
Uplink Tech.
SC-FDMA
OFDMA
SC-FDMA reduces PAPR on uplink, but increases complexity
Framing
1 ms
5 ms
Faster framing reduces latency for real-time apps
Subcarrier Spacing
15 kHz
10.94 kHz
Trade-off between robustness against ICI (higher mobility) and overhead loss due to CP
Resource Allocation
Persistent and Non-persistent
Non-persistent (valid within one frame)
Persistent allocation option is more efficient, reduces signaling overhead
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SC-FDMA improves cell-edge uplink performance for LTE by avoiding PAPR. This performance improvement is achieved at the expense of greater complexity. So, this leaves us to look at other areas to distinguish the technologies. Since mobile WiMAX was at its conception intended for high-speed data, not specifically voice communications, some areas of LTE are optimized to provide better performance for VoIP than WiMAX, such as smaller frame sizes. LTE also targets at very high mobility. Additionally, since LTE must support compatibility with earlier 3GPP technologies, it includes inter-radio technology handover in its inception. This said, there is very little difference between the candidate 4G technologies. WiMAX and LTE continue to learn from each other and will continue to evolve their respective capabilities. For example, WiMAX Release 1.5 will include features to optimize for VoIP, and will offer inter-radio access technology handover for several technologies including Wi-Fi, EV-DO, HSPA, and LTE.
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A | Additional Topics
Comparing Peak Data and Availability
Speed (Mbps)
>100
802.11n
LTE Mobile WiMAX
WiMAX
50
Wi-Fi HSDPA+
10 3
HSDPA
1xEV-DO (Rev B)
1xEV-DO 2002
2006 Availability
2008
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This diagram compares the peak data rate capabilities of various wireless networks and puts them against the timeline in terms of their availability. •
Around 2002: CDMA2000 1x systems evolved to support higher data rates of 2.45 Mbps in the downlink. This uses the channel bandwidth of 1.25 MHz. In those days, Wi-Fi was already popular and delivering data rates of 11 Mbps in 802.11b and up to 54 Mbps in 802.11g. However, notice that the coverage of Wi-Fi is very limited and uses a much larger bandwidth in the unlicensed spectrum.
•
Around 2006: The UMTS evolution of HSDPA offers a peak data rate of 14 Mbps in the 5 MHz channel bandwidth. However, the practical data rates are in the range of 3.6 Mbps. WiMAX, however, offers data rates in the range of 50 Mbps in the 20 MHz channel bandwidth.
rates greater than 100 Mbps. Later, Long Term Evolution (LTE) will deliver peak data rates in the range of 50 to 100 Mbps.
Moving forward, HSPA+ will provide the peak data rate of 42 Mbps and 1xEV-DO (Rev B) can put multiple 1xEV-DO carriers together to offer the data rates of 15 * 3 = 45 Mbps in a 20 MHz bandwidth. 802.11n will support data
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A | Additional Topics
A Comparative View 1xEV-DO Rev A
HSDPA and HSUPA
HSPA+
LTE Rel 8
WiMAX 802.16e
DL Data Rates (Mbps) (Theoretical Max)
3.1
14
28-42
Up to 300
75-300
UL Data Rates (Mbps) (Theoretical Max)
1.8
5.7
11
Up to 75
25-75
Channel Bandwidth
1.25
5
5
Up to 20
Up to 20
Standard Availability
2004
04-05
2007-08
2007-08
2005
LTE and WiMAX data rates are comparable for similar RF parameters such as bandwidth, number of antenna, etc.
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This chart provides a summary of the key aspects of the 4G competitive landscape.
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A | Additional Topics
Interworking with 3GPP
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Interworking with 3GPP (Rel-8) S12 (for direct tunnel)
UTRAN GERAN
Rel 8 SGSN S4 S3
MME
S-GW
HSS
S5/S8
P-GW
IP services or Internet
EPC
E-UTRAN
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This slide shows the interworking architecture between LTE and Release 8 UTRAN/GERAN. New interfaces - S3, S4, and S12 - are added in Rel 8 UMTS/GPRS networks. The Rel 8 SGSN will communicate with the MME over the S3 interface for handover signaling messages, and communicate with the S-GW over the S4 for user plane data traffic. Also, a direct tunnel for data traffic can be established between the RNC in UMTS and the S-GW in LTE to reduce delay. Note that the S-GW is the mobility anchor here, not the P-GW.
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A | Additional Topics
Interworking with 1x/1xEV-DO
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A | Additional Topics
LTE-1x/1xEVDO Interworking Architecture HSS
IP Services
SWx 3GPP
AAA S6b
E-UTRAN
MME
S-GW
P-GW PCRF
S101 (Pre-Reg/HO Signaling)
S103 (Data S2a forwarding) (MIP)
1xEV-DO AN
Gxa (QoS)
STa (Authentication)
PDSN
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This slide shows the interworking architecture between LTE and 1x/1xEV-DO. There are five new interfaces needed. The S101 interface between the MME and 1xEVDO sets up a transparent tunnel and carries the preregistration and handover signaling messages. The S103 interface enables data forwarding during handover. The S2a interface between the P-GW and PDSN supports Mobile IP and carriers user-plane data traffic. The Gxa interface supports QoS mapping during handover. A new entity – the 3GPP AAA server - is added in the LTE core network to act as a broker between the HSS and PDSN. The STa interface between the AAA server and the PDSN supports authentication.
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A | Additional Topics
LTE Performance
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LTE DL Spectrum Efficiency and User Throughput Spectral Efficiency (bps/Hz/cell) Case 1
Mean User Thpt (bps/Hz/user) Case 1
Spectral Efficiency (bps/Hz/cell) case 3
3
0.3
2.67 2.41
2.5 1.87
2
1.69
Mean User Thpt (bps/Hz/user) case 3 0.27
0.24
0.25
1.85
0.19 0.19
0.2
0.17
1.56
0.16
0.15
1.5
0.1
1 0.53
0.52
0.5
0.05
0
0
UTRA baseline (1x2)
SU-MIMO (2x2)
SU-MIMO (4x2)
0.09 0.08 0.07 0.06 0.05 0.04 0.03 0.02 0.01 0
UTRA baseline (1x2)
SU-MIMO (4x4)
Cell-edge User Thpt (bps/Hz/user) Case 1
0.05 0.05
SU-MIMO (4x2)
SU-MIMO (4x4)
Cell-edge User Thpt (bps/Hz/user) case 3 0.08 0.08
0.06
0.05
0.05 0.04
0.02 0.02
UTRA baseline (1x2)
SU-MIMO (2x2)
SU-MIMO (2x2)
SU-MIMO (4x2)
SU-MIMO (4x4)
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- Assume 10 users per cell on average and a homogenous user distribution - Case 1: inter-site distance = 500 m - Case 3: inter-site distance = 1732 m Source: www.3GPP.org
This slide shows the LTE DL spectrum efficiency and user throughput performance simulation conducted by 3GPP. The UTRA baseline is given in the first bar on the left. The other three scenarios are for E-UTRA. It is noted that increasing the number of antennas improves spectral efficiency and throughput. The performance of Case 1 (500 m inter-site distance) is slightly better than Case 3 (1732 m inter-site distance). Also, when an MS moves to the cell edge, a throughput decrease is expected.
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LTE UL Spectrum Efficiency and User Throughput Spectral Efficiency (bps/Hz/cell) Case 1 1.2
Spectral Efficiency (bps/Hz/cell) case 3 1.103
Mean User Thpt (bps/Hz/user) Case 1 0.12
1.038
1
0.11
0.104
0.1 0.735
0.8
0.681
0.675
0.08
0.073
0.622
0.068
0.067
0.062
0.06
0.6 0.4
Mean User Thpt (bps/Hz/user) case 3
0.04
0.332 0.316
0.033 0.032
0.02
0.2
0
0 UTRA baseline
1x2
1x4
UTRA baseline
1x2 (MU-MIMO)
Cell-edge User Thpt (bps/Hz/user) Case 1
0.052
0.05 0.04 0.024
0.023
0.02 0.01
0.0094
0.009 0.0023
1x4
1x2 (MU-MIMO)
Cell-edge User Thpt (bps/Hz/user) case 3
0.06
0.03
1x2
0.0044
0.0023
- Assume 10 users per cell on average and a homogenous user distribution - Case 1: inter-site distance = 500 m - Case 3: inter-site distance = 1732 m
0 UTRA baseline
1x2
1x4
1x2 (MU-MIMO)
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Source: www.3GPP.org
This slide shows the LTE UL spectrum efficiency and user throughput performance simulation conducted by 3GPP. The performance of Case 1 (500 m inter-site distance) is better than Case 3 (1732 m inter-site distance). The UTRA baseline is given in the first bar on the left. The other three scenarios are for E-UTRA. It is noted that increasing the number of receiving antennas at the BS from two to four significantly improves spectral efficiency and throughput. The use of 1x2 MUMIMO can increase the cell capacity without impacting the user throughput too much. But, using 2x2 SU-MIMO does not improve the user throughput performance. Also, when an MS moves to the cell edge, the user’s cell edge throughput is low (as expected). The cell edge data rate in a large cell (Case 3) is significantly low compared to that of a small cell (Case 1).
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A | Additional Topics
Summary • Similarities among various 4G systems include: – High data rates and low latency, – Voice supported by VoIP, – Use of OFDM and multiple-antenna techniques to achieve high data rates, – Flat all-IP architecture and reduced nodes compared to 3G wireless systems, and – Use of a scalable channel bandwidth up to 20 MHz.
• Differences among various 4G systems include: – Initial deployments of Mobile WiMAX in TDD mode, whereas LTE deployments are in FDD mode.
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Acronyms
1xEV-DO 2G 3G 3GPP 3GPP2 4G AAA ACK AMR AN AS AS AuC BCCH BPSK BS BTS BWA C-RNTI CAPEX CDMA CP CQI CSCF DL DSCP DSP E-UTRA E-UTRAN eBS EDGE eNB eNodeB EPC ePDG EPS EV-DO FA FA FDD FDM
1x Evolution for Data Optimized Second Generation Wireless Systems Third Generation Wireless Systems Third Generation Partnership Project Third Generation Partnership Project 2 Fourth Generation Wireless Systems Authentication, Authorization and Accounting Acknowledge or Acknowledgement Adaptive Multi-Rate Access Network Access Stratum Application Server Authentication Center Broadcast Control Channel Binary Phase Shift Keying Base Station Base Transceiver Station Broadband Wireless Access Cell Radio Network Temporary Identity Capital Expenditure Code Division Multiple Access Cyclic Prefix Channel Quality Indicator Call Session Control Function Downlink Differentiated Services Code Point Digital Signal Processing Evolved Universal Terrestrial Radio Access Evolved Universal Terrestrial Radio Access Network evolved Base Station Enhanced Data Rates for Global Evolution E-UTRAN Node B or Evolved Node B E-UTRAN Node B or Evolved Node B Evolved Packet Core Evolved Packet Data Gateway Evolved Packet System Evolution for Data Optimized Foreign Agent Frequency Allocation Frequency Division Duplex Frequency Division Multiplexing
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Acronyms
FDMA FER FFT FM FTP FTTH FTTP GERAN GGSN GHz GPRS GRE GSM GTP GUTI GW H-FDD HA HARQ HLR HO HSDPA HSPA HSS HSUPA ICI IEEE IFFT IMEI IMS IMSI IP ISI ISUP kbps LAN LEC LTE MBMS MCC MCM
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Frequency Division Multiple Access Frame Error Rate Fast Fourier Transform Frequency Modulation File Transfer Protocol Fiber-to-the-Home Fiber-to-the-Premise GSM EDGE Radio Access Network Gateway GPRS Support Node GigaHertz General Packet Radio Service Generic Routing Encapsulation Global System for Mobile Communication GPRS Tunneling Protocol Globally Unique Temporary Identity Gateway Half-Frequency Division Duplex Home Agent Hybrid ARQ Home Location Register Handover High Speed Downlink Packet Access High Speed Packet Access Home Subscriber Server High Speed Uplink Packet Access Inter-Carrier Interference Institute of Electrical and Electronics Engineers Inverse Fast Fourier Transform International Mobile Equipment Identity IP Multimedia Subsystem International Mobile Subscriber Identity Internet Protocol Inter-Symbol Interference ISDN (Integrated Services Digital Network) Signaling User Part kilo-bits per second Local Area Network Local Exchange Carrier Long Term Evolution Multimedia Broadcast Multicast Service Mobile Country Code Multi-Carrier Modulation
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Acronyms
ME MGCF MGW MHz MIMO MIP MME MMS MNC MU-MIMO NACK NAS OFDM OFDMA OPEX P-GW PAPR PCEF PCRF PDCCH PDSCH PDN PDP PDP PDSN PLMN PRB PS-CN PSTN PUCCH PUSCH QAM QCI QoS QPSK RAN RF RNC RRC RRM S-GW
Mobile Equipment Media Gateway Control Function Media Gateway Mega Hertz Multiple Input Multiple Output Mobile IP Mobility Management Entity Multimedia Messaging Service Mobile Network Code Multi-User MIMO Negative ACK Non-Access Stratum Orthogonal Frequency Division Multiplexing Orthogonal Frequency Division Multiple Access Operating Expenditure PDN Gateway Peak-to-Average Power Ratio Policy and Charging Enforcement Function Policy and Charging Rules Function Physical Downlink Control Channel Physical Downlink Shared Channel Packet Data Network or Public Data Network Packet Data Protocol Policy Decision Point Packet Data Serving Node Public Land Mobile Network Physical Resource Block Packet Switched Core Network Public Switched Telephone Network Physical Uplink Control Channel Physical Uplink Shared Channel Quadrature Amplitude Modulation QoS Class Identifier Quality of Service Quadrature Phase Shift Keying Radio Access Network Radio Frequency Radio Network Controller Radio Resource Control Radio Resource Management Serving Gateway
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Acronyms
S1-U SC-FDMA SCTP SDMA SGSN SGW SIM SIP SMS SOFDMA STK SU-MIMO TCP TD-CDMA TDD TDMA TTI UE UL UL-SCH UMB UMTS USIM UTRA UTRAN VAF VoIP WCDMA Wi-Fi WiMAX WLAN
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S1 - User Plane Single Carrier - Frequency Division Multiple Access Stream Control Transmission Protocol Space (or Spatial) Division Multiple Access Serving GPRS Support Node Signaling Gateway Subscriber Identity Module Session Initiation Protocol Short Message Service Scalable OFDMA SIM Tool Kit Single User MIMO Transmission Control Protocol Time Division-Code Division Multiple Access Time Division Duplex Time Division Multiple Access Transmission Time Interval User Equipment Uplink Uplink Shared Channel Ultra Mobile Broadband Universal Mobile Telecommunications System Universal Subscriber Identity Module Universal Terrestrial Radio Access Universal Terrestrial Radio Access Network Voice Activity Factor Voice over Internet Protocol Wideband Code Division Multiple Access Wireless Fidelity Worldwide Interoperability for Microwave Access Wireless Local Area Networks
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References
Standards 1. 2. 3. 4. 5.
3GPP TS 36.211: “Physical Channels and Modulation” 3GPP TS 36.212: “Multiplexing and channel coding” 3GPP TS 36.213: “Physical layer procedures” 3GPP TS 36.300: “E-UTRA and E-UTRAN Overall description; stage 2” 3GPP TS 36.306: “Evolved Universal Terrestrial Radio Access (E-UTRA) User Equipment (UE) radio access capabilities” 6. 3GPP TR 25.814: “Physical layer aspects for Evolved UTRA” 7. 3GPP TR 23.882: “3GPP System Architecture Evolution” 8. 3GPP TS 23.401: “System Architecture Evolution: GPRS enhancements for LTE access” 9. 3GPP TS 23.402: “Architecture Enhancements for non-3GPP accesses” 10. 3GPP TR 25.913: “Requirements of Evolved UTRA and Evolved UTRAN” 11. 3GPP TS 23.203: “Policy and charging control architecture”
IEEE Papers 1. 2. 3. 4.
Junsung Lim, “Adaptive radio resource management for uplink wireless networks”, Ph.D dissertation, Polytechnic University. Junsung Lim et al., “Peak-to-average power ratio of SC-FDMA signals with pulse shaping”, IEEE international symposium on PIMRC, 2006. Hyung G Myung et al., “Single carrier FDMA for uplink wireless transmission”, IEEE vehicular technology magazine, September 2006. “Toward Global Mobile Broadband,” UMTS Forum, February 2008.
Web Sites 1. 2. 3. 4. 5. 6.
Third Generation Partnership Project (3GPP) Homepage – www.3GPP.org European Telecommunications Standards Institute – www.etsi.org UMTS Forum – www.umts-forum.org CDMA Development Group – www.cdg.org 3G and 4G Comparison - www.mobileinfo.com/3G/4GVision&Technologies.htm White paper “Mobile Broadband: The Global Evolution of UMTS/HSPA – 3GPP Release 7 and Beyond” www.3gamericas.org/documents/UMTS_Rel7_Beyond_Dec2006.pdf
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