SRAN
GU Refarming Network Solution
Issue Date
3.0 2012-09-28
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HUAWEI TECHNOLOGIES CO., LTD.
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SRAN GU Refarming Network Solution
About This Document
About This Document Author Prepared by
Date
2012-06-07
Reviewed by
Date
yyyy-mm-dd
Reviewed by
Date
yyyy-mm-dd
Granted by
Date
yyyy-mm-dd
SRAN Solution Design Department
Change History Date
Versio n
Description
Author
2009-09-25
0.5
Completed the first draft.
Chen Shuai
2009-09-29
0.6
Modified the first draft.
Xiong Bin
2009-11-05
0.9
Completed the initial release.
Yang Liping
2009-12-26
1.0
Added chapter 8.
Yang Liping
2010-1-10
1.1
Updated the data of nonstandard frequency separation. Added interference cancelation combining such as ICC, EICC, and SAIC that are related to Refarming large capacity.
2010-9-10
2.0
Added the following information: Advantages of 900 MHz Refarming The application scenario and deployment policy of Refarming The definitions of nonstandard bandwidth and nonstandard frequency separation The instruction to the application of flexible nonstandard bandwidth
SRAN GU Refarming Network Solution
Date
About This Document
Versio n
Description
Author
The contents about frequencies with nonstandard separation not used in indoor GSM cells, frequencies with nonstandard separation not used in cells requiring large UMTS capacity, and enabling the UPA algorithm for resisting strong interference. Added buffer zone planning method on the live network. Rewrote the GSM network optimization measures after Refarming for delivery. Added per-sales performance solutions of Refarming. Added implementation steps of UMTS900 in the project implementation. Added the instruction to the difference between UO products and the Refarming. 2011-8-15
2.3
Added the instruction to UMTS900 capacity gain. Updated the Refarming antenna solution. Added the impact of GSM frequency reuse on network performance, including the network simulations and KPI assessments when different frequency reuse patterns are adopted. Added chapter 11.
2012-5-15
3.0
Rewrote the document based on the procedures of delivering the Refarming service products.
Li Guowei
SRAN GU Refarming Network Solution
Contents
1
Contents
About This Document.......................................................................ii Preface........................................................................................... 1 1 Refarming Overview......................................................................2 1.1 What is Refarming?...........................................................................................................................................2 1.2 Why the GU 900 MHz Refarming.....................................................................................................................2 1.3 Challenges of the GU 900 MHz Refarming......................................................................................................3
2 Refarming Solution Procedures......................................................4 2.1 Procedures for Designing the Pre-Sale Refarming Solution..............................................................................4 2.2 Procedures for Delivering the Refarming Solution...........................................................................................6
3 GSM Part...................................................................................... 7 3.1 Network Assessment..........................................................................................................................................7 3.1.1 GSM KPIs Assessment.............................................................................................................................7 3.1.2 UMTS900 Terminal Penetration Rate Assessment...................................................................................7 3.1.3 GSM Frequency Plan Analysis.................................................................................................................8 3.1.4 GBSS Feature Analysis............................................................................................................................8 3.2 Solution Design..................................................................................................................................................8 3.2.1 Interference Analysis for GU Nonstandard Frequency Spacing..............................................................8 3.2.2 Frequency Allocation Between GSM and UMTS Networks..................................................................17 3.2.3 GU Intra-Frequency Buffer Zone Planning............................................................................................23 3.2.4 GUL Inter_Rat Mobility Solution..........................................................................................................26 3.2.5 GSM Traffic Transfer Solution...............................................................................................................27 3.3 Implementation................................................................................................................................................29 3.3.1 Delivery Solutions..................................................................................................................................29 3.3.2 Implementation Procedures....................................................................................................................32 3.4 Network Optimization and Acceptance...........................................................................................................33 3.4.1 Network Optimization............................................................................................................................33 3.4.2 GSM Network Acceptance.....................................................................................................................34
SRAN GU Refarming Network Solution
Contents
4 UMTS Part..................................................................................35 4.1 Network Assessment........................................................................................................................................35 4.1.1 Assessment and Analysis of KPIs...........................................................................................................35 4.1.2 UMTS900 Coverage/Capacity Assessment............................................................................................36 4.1.3 Identifying UMTS Value Areas..............................................................................................................36 4.2 Solution Planning.............................................................................................................................................37 4.2.1 Antenna Solutions...................................................................................................................................37 4.2.2 UMTS Inter-Carrier Mobility Solution..................................................................................................41 4.2.3 Power Configuration Analysis................................................................................................................41 4.2.4 Parameter Configuration.........................................................................................................................42 4.3 Network Implementation.................................................................................................................................43 4.3.1 Policy for Deploying the UMTS900......................................................................................................43 4.3.2 UMTS900 Hardware Installation...........................................................................................................43 4.3.3 Activating the UMTS900........................................................................................................................43 4.3.4 Setting the UMTS Filter.........................................................................................................................44 4.4 Network Optimization and Acceptance...........................................................................................................44 4.4.1 UMTS Network Optimization................................................................................................................44 4.4.2 UMTS Network Acceptance...................................................................................................................45
5 Refarming Scenarios...................................................................46 Reference Documents....................................................................47
SRAN GU Refarming Network Solution
0Preface
Preface UMTS900 has advantages over UMTS2100. This drives most operators to reduce cost by deploying the UMTS900 network. Due to the frequency resource limitation, those operators cannot free a GSM 900 MHz frequency band of 5 MHz for Refarming. Therefore, they focus on the GU 900 MHz Refarming of a nonstandard bandwidth, such as 3.8 MHz, 4.2 MHz, or 4.6 MHz. To meet operators' requirements, this document provides the solution for the GU 900 MHz Refarming of 3.8 MHz, 4.2 MHz, or 4.6 MHz. This document is mapping with SRAN3.0 or later versions. The GU 900 MHz Refarming of 3.8 MHz is supported in SRAN6.0 or later versions. For reasons of simplicity and clarity, this document discusses 900 MHz Refarming. All the statements apply equally to 850 MHz Refarming.
Issue 3.0 (2012-09-28)
Huawei Proprietary and Confidential Copyright © Huawei Technologies Co., Ltd.
1
SRAN GU Refarming Network Solution
0Reference Documents
1
Refarming Overview
1.1 What is Refarming? Refarming is a strategy that telecom operators reuse their frequency resources and introduce new radio communication technologies to improve the spectral efficiency and data throughput. For example, the mainstream GU 900 MHz Refarming solution is that operators free about 5 MHz of the GSM on the 900 MHz band and deploy UMTS on the 900 MHz frequency band. On July 27, 2009, all 27 EU telecom ministers approved a 900 MHz Refarming bill that all the member countries are required to implement in six months to drive up the development of 3G mobile communication. The operators with the 900 MHz spectrum resources can put their spectrum Refarming plans in practice and use their desired mobile communication technologies in the 900 MHz frequency band without license restriction.
1.2 Why the GU 900 MHz Refarming The advantages of implementing the GU 900 MHz Refarming are as follows:
Gains in spectral efficiency The 900 MHz devices are most commonly used. Industry statistics show that by the end of 2008, about 80% of wireless devices work in the 900 MHz frequency band. By the end of 2009, the GSM900 license may be expired for many equipment suppliers and they have to apply for a license extension. In July, 2009, EU passed a resolution that the GSM900 band can be used for UMTS. In this manner, some operators can deploy a UMTS network without purchasing any UMTS licenses.
Gains in coverage UMTS900 has a 7 dB path loss advantage over UMTS2100 in free space conditions. This advantage can be more than 20 dB in indoor scenarios. For details, see reference [1]. As a result, the deployment of UMTS900 saves equipment cost by reducing the number of sites in suburban areas and provides a better and deeper indoor coverage in urban areas.
Gains in capacity In coverage-limited and non-interference-limited scenarios (for example, deep coverage areas in densely-populated urban areas or cell edge areas in suburban areas), UMTS900
SRAN GU Refarming Network Solution
0Reference Documents
has larger throughput and capacity than UMTS2100 since UMTS900 has higher receive levels and Ec/Io. In the interference-limited scenario, capacity gains brought by UMTS900 coverage are reduced when interference increases. As a result, the UMTS900 coverage does not have gains in this scenario.
Maturity of UMTS900 terminal industry chains A large-scale industry chain of the UMTS900 terminals has taken shape. Based on GSA investigation, until February, 2012, the total number of the UMTS900 terminals has reached 719. It is predicted that by 2015, the market penetration rate of the UMTS900 terminals will reach 100%. As a result, more and more operators plan to improve their competitiveness by implementing the GU 900 MHz Refarming and the GU 900 MHz Refarming is becoming the trend in the industry.
1.3 Challenges of the GU 900 MHz Refarming The GU 900 MHz Refarming also brings challenges to network planning and may affect network performance. The following are operators' concerns about implementing the GU 900 MHz Refarming:
How to reduce co-channel and adjacent-channel interference between GSM900 and UMTS900 networks
After the Refarming, the GSM frequency resources are greatly reduced. In this case, how to smoothly transfer GSM900 traffic to the GSM1800 or UMTS900 network to keep the GSM network quality
Whether the antenna of the GSM900 network can be reused by the UMTS900 network with network quality kept and cost saved
How to balance traffic load among the GSM, UMTS, and LTE networks after the UMTS900 deployment The preceding questions are of great concerns to the operators and are the key to the success of the GU 900 MHz Refarming solution.
2
Refarming Solution Procedures
2.1 Procedures for Designing the Pre-Sale Refarming Solution With the increase of Refarming projects, field pre-sales personnel raise more specific requirements for the performance and the implementation of the Refarming solution, and require Huawei to provide a pertinent and feasible Refarming solution. This chapter aims at guiding the field pre-sales personnel how to provide a feasible Refarming performance solution as well as how to make sales and delivery policies. This chapter also gives a detailed depiction by using examples.
Figure 2.1.1.I.1.1.1 Flowchart for designing the pre-sale Refarming solution
The preceding flowchart is for a general Refarming solution. The flowchart for a specific Refarming solution varies based on the following factors: frequency reuse coefficient, the coverage of DCS1800, the ratio of traffic intensity to the number of TCHs, and the proportion of traffic carried over half-rate TCHs (TCHHs).
2.2 Procedures for Delivering the Refarming Solution Huawei has developed Refarming service products which are divided into GSM and UMTS groups. Each group consists of four procedures: network assessment, solution design, network implementation, and network optimization acceptance. The following figure shows procedures for delivering Refarming service products. Figure 2.2.1.I.1.1.1 Delivery procedures
Delivery personnel should understand some or all of the above topics as required to ensure a better delivery.
3
GSM Part
3.1 Network Assessment 3.1.1 GSM KPIs Assessment 1.
Collecting KPIs of the live network For more details about the collected KPIs and recommended equations, see GU Refarming Network solution 3.0_annex 1_GSM KPI.xls. The recommended equations in the document can be modified as required.
2.
Commitment of KPIs after the Refarming During bidding clarification, do not promise that the KPI does not deteriorate after the Refarming. Any KPI commitment must be reviewed by Huawei KPI Auditing committee before being made to customers.
3.1.2 UMTS900 Terminal Penetration Rate Assessment Currently, the penetration rate of UMTS900 terminals cannot be calculated based on traffic statistics counters. Calculate the UMTS900 penetration rate as follows: 1.
Obtain it from customers.
2.
Obtain the terminals' IMEIs from the core network (CN). The UMTS900 terminal penetration rate can be calculated based on the obtained IMEIs because the IEMIs indicate terminal types and radio access (RA) capability.
The penetration rate of UMTS900 terminals in the GSM network is important for calculating the amount of traffic in the GSM network that can be transferred to the UMTS900 network. To calculate this rate, do as follows: 1
Calculate the penetration rate of UMTS terminals based on the Measurement of MS Capability counters A03624: Number of Calls Originated or Terminated by MSs Supporting FDD and A03604: Number of Calls Originated or Terminated by MSs Supporting Early Classmark Sending.
2
Obtain the penetration rate of UMTS900 terminals among all the UMTS terminals.
3
Calculate the penetration rate of UMTS900 terminals in the GSM network based on the preceding two figures.
Take the GSM network of operator V in country E as an example. The penetration rate of UMTS terminals in the GSM network is about 6% based on relevant counters while the penetration rate of UMTS900 terminals in all the UMTS terminals is about 15% (This number is obtained from the customer). As a result, the proportion of traffic in the GSM network that can be transferred to the UMTS900 network after the Refarming is 6% x 15% = 0.9%. The figure 0.9% indicates that little traffic in the GSM network can be transferred to the UMTS network.
2 GSM Frequency Plan Analysis To reuse the GSM frequency, you can allocate frequencies to BCCHs and TCHs separately or together.
Allocating frequencies to BCCHs and TCHs separately In this case, the frequency reuse coefficients of BCCHs and TCHs are calculated separately. Assume that the number of frequencies occupied by BCCHs in the GSM network is M, that of frequencies occupied by TCHs in the GSM network is N, and the average number of carriers configured for a cell is X.
If the frequency reuse mode of the TCH is none-FH or baseband FH, the frequency reuse coefficient of the BCCH is M and that of the TCH is N/(X–1).
If the frequency reuse pattern of the TCH is RF FH, the frequency reuse coefficient of the BCCH is M. The frequency reuse pattern of the TCH can be 1x1 or 1x3. FRLOAD = 3x(X–1)N.
Allocating frequencies to BCCHs and TCHs combinedly In this case, BCCHs and TCHs use the same frequencies. As a result, the frequency reuse coefficients of the two are the same. Assume that the number of frequencies available in the network is W, the average number of carriers configured for a cell is X. The frequency reuse coefficient of the network is W/X. After the Refarming, the GSM traffic will be transferred to the UMTS network to ensure that the frequency reuse coefficient of the GSM900 network remains the same. In this way, the GSM network quality, which greatly relies on its frequency reuse coefficient, is maintained. For details about transferring GSM traffic, see section 25GSM Traffic Transfer Solution.
3 GBSS Feature Analysis To make a detailed network planning and optimization scheme after the Refarming, you must first check the enabled features in the live network since the GBSS network performance is closely related to the enabled features. For the key features that must be checked, see the GSM Feature Audit List.
2 Solution Design 1 Interference Analysis for GU Nonstandard Frequency Spacing This section only provides a simple analysis on the interference between the GSM and UMTS networks. For more details, see the WRFD-021001 Flexible Frequency Bandwidth of UMTS 4.2 MHz Carrier Technical White Paper and MRFD-221703 2.0MHz Central Frequency Point Separation between GSM and UMTS Mode Technical White Paper.
UMTS Nonstandard Bandwidth The power spectrum of the UMTS is concentrated within 4.2 MHz around its center frequency (depending on the filter capability of the NodeB). Therefore, the frequencies with low power density at the edge of the UMTS spectrum can be used for GSM carriers, as shown in 1. The nonstandard filter is steeper than the standard 5 MHz one. Compared with the standard 5 MHz UMTS, the nonstandard UMTS can provide another one-to-six GSM carriers at each side for operators. 1
GU power spectrum of small separation application 4.2MHz steeper filter
2.2MHz 2.6MHz
If the spacing between the center GSM and UMTS frequencies is larger than 2.6 MHz, the UMTS uses a standard bandwidth of 5 MHz; if that spacing is 2.0 MHz, 2.2 MHz, or 2.4 MHz, the UMTS uses a nonstandard bandwidth of 3.8 MHz, 4.2 MHz, or 4.6 MHz, respectively. A UMTS bandwidth less than 5 MHz is regarded as a nonstandard UMTS bandwidth. The GSM frequencies less than 2.6 MHz away from the center UMTS frequency are regarded as small-spaced frequencies. 2 shows the flexible frequency spacing between the GSM and UMTS frequencies.
2
Flexible frequency spacing
U5.0M
2.6MHz
U4.8M
2.6MHz
2.4MHz
U
2.6MHz
U
2.4MHz
2.4MHz
2.2MHz
2.4MHz
U4.0M U
2.2MHz
2.2MHz
U3.8M
2.0MHz
2.0MHz
2.0MHz
2.2MHz
(1)
When the nonstandard UMTS bandwidth feature is enabled, a nonstandard filter is used on the NodeB side for transmitting and receiving signals while a 5 MHz standard filter is still used on the UE.
(2)
Versions earlier than SRAN6.0 only support the nonstandard UMTS bandwidth of 4.2 MHz or 4.6 MHz. The nonstandard UMTS bandwidth of 3.8 MHz is supported by SRAN 6.0 or later versions.
(3)
The spacing between the center GSM and UMTS frequencies must be an integer multiple of 0.2 MHz. Therefore, the spacing can only be 2.2 MHz, 2.4 MHz, or 2.6 MHz and cannot be 2.1 MHz, 2.3 MHz, or 2.5 MHz.
(4)
The GU 900 MHz Refarming of 4.2 MHz solution has been verified in both urban and suburban areas. As a result, this solution can be implemented on a large scale.
(5)
The GU 900 MHz Refarming of 3.8 MHz solution has not been verified in urban areas and is only recommended in suburban areas.
The standard spacing between the center UMTS frequencies is 5 MHz. If that spacing is less than 5 MHz, for example, 4.8 MHz, 4.6 MHz, 4.4 MHz, 4.2 MHz, 4.0 MHz, or 3.8 MHz, nonstandard spacing is used between two UMTS carriers. The smaller the spacing between the center GSM and UMTS frequencies or between the center UMTS frequencies is, the greater the co-channel or adjacent-channel frequency interference between different RATs is. As a result, the impact on relevant KPIs is greater. Not all the GSM cells use ARFCNs with nonstandard frequency separation after the 900 MHz Refarming solution is implemented. In fact, the GSM uses ARFCNs with nonstandard frequency separation according to different frequency reuse modes. 3 shows the application of small frequency separation. 3
Application of small frequency spacing
In 3, the UMTS bandwidth is 4.2 Mbit/s, the GSM is in S2/2/2 mode, and ARFCNs with the separations of 2.2 MHz, 2.4 MHz, and 2.6 MHz are distributed in each cell in 4 x 3 reuse mode. The minimum GU frequency separation of each cell varies with the GSM ARFCNs. Not all the cells have the same GU frequency separation. As shown in 2I111, in the UMTS4.2 M solution, the GU frequency separation of a cell can be 2.2 MHz, 2.4 MHz, or 2.6 MHz
Application Scenarios for GU Small Frequency Separation Since UU small frequency spacing only applies to UMTS co-located sites, this chapter only compares differences between co-located and separate sites for GU small frequency spacing. In the case of GU joint networking, the coverage range of the GSM differs from that of the UMTS due to the two RATS's differences in receiver sensitivity, transmit power, and demodulation threshold. Therefore, GU co-located sites or UMTS sites can be used for UMTS network construction. For details, see the reference[3]. spacing
Separate sites Separate UMTS sites have the following advantages: Compared with the GSM, the UMTS supports a larger coverage range. If separate UMTS sites are used, fewer UMTS sites are required and the equipment investment is reduced, so that the equipment investment on UMTS sited is decreased. Separate UMTS sites, however, also have the following disadvantages:
If separate UMTS sites are used, the network cannot be deployed according to the original cell structure. Therefore, the original site resources cannot be used in most cases and a large number of new sites must be constructed. The auxiliary investment increases (currently, the site investment occupies a large percentage of the operation expenditure).
Mutual interference between the GSM and the UMTS increases. As shown in 1, if a terminal (user equipment or mobile station) of either system is located at the edge of a cell of the local system but near to the base station of another system, the terminal generates the severest interference to the uplink of the other system when initiating a call. At the same time, the terminal is also interfered by the downlink of the other system. This is called "near-far effect". Therefore, the standard UMTS bandwidth of 5 MHz is recommended for separate UMTS sites. The UMTS sites of an operator are not located on the same site with the GSM sites of another operator in most cases. The networking solution should be designed according to the worst condition. To avoid interference between UMTS sites of one operator and the GSM sites of another operator, the GU frequency separation should be kept 2.6 MHz at least.
1
"Near-far effect" in the case of separate UMTS sites
Co-located sites GU co-located sites have the following advantages: The auxiliary investment is reduced because no new site must be constructed. GU co-located sites, however, also have the following disadvantage: Compared with separate UMTS sites, GU co-located sites require more UMTS equipment. Therefore, part of the equipment investment is wasted in the early stage when the UMTS service is not widely required.
2
Interference between a terminal of a RAT and the co-located base station of another RAT
For the scenario of GU co-located sites, the impact of "near-far effect" is small since the free space path loss from a terminal to its local system is the same as that from the terminal to the other system. Therefore, if the nonstandard UMTS bandwidth is used, it is recommended that one UMTS900 network be deployed in each GSM900 site. For some GSM900 cells where UMTS900 cannot be deployed, the GU small frequency spacing cannot be applied. Otherwise, strong interference between the two systems will occur. The standard UMTS 5 MHz bandwidth is recommended when GSM and UMTS sites are uncoordinated. In this scenario, the impact of GU small frequency spacing on network
performance cannot be assessed because we cannot access the interference between the two systems.
Analysis of Interference Between the GSM and the UMTS Both the GSM and the UMTS are deployed on the 900 MHz frequency band. The GSM uplink is close to the UMTS uplink, and the GSM downlink is also close to the UMTS downlink. The interference analysis focuses on the interference between BSs and terminals. The following describes interference analysis based on the adjacent channel selectivity (ACS) and the adjacent channel leakage power ratio (ACLR). As shown in 1, the interference between the GSM and the UMTS for 900 MHz Refarming is classified into four types according to interfered and interfering objects. 1
Interference between the GSM and the UMTS
GSM BTS
UMTS BS
(4) (1)
(3) (2)
GSM MS
UMTS UE
The green arrows indicate wanted signals and the red arrows indicate interfering signals. In the case of SRAN networking, the GSM BTSs are generally co-located with the UMTS NodeBs. They are separated in the figure only t The figure shows that the following types of inter-system interference exist when the UMTS900 coexists with the GSM900:
Interference caused by the GSM BTS to the downlink of the UMTS UE: This interference depends on ACLR of the GSM BTS and ACS of the UMTS UE.
Interference caused by the GSM MS to the uplink of the UMTS NodeB: This interference depends on ACLR of the GSM MS and ACS of the UMTS NodeB.
Interference caused by the UMTS NodeB to the downlink of the GSM MS: This interference depends on ACLR of the UMTS NodeB and ACS of the GSM MS.
Interference caused by the UMTS UE to the uplink of the GSM BTS: This interference depends on ACLR of the UMTS UE and ACS of the GSM BTS.
Interference caused by the UMTS UE to the uplink of the GSM BTS is small because the transmission power of the UE can be better controlled in the UMTS network.
The power received by the interfered system from the interfering system equals the transmit power of the interfering system minus the ACIR in Refarming scenarios. Therefore, the interference severity depends on the ACIR. The ACIR, however, is limited by the small one between the ACLR of the interfering system and the ACS of the interfered system. The interference bottlenecks can be analyzed according to the ACLR and the ACS of Huawei SRAN BSs in the GSM and the UMTS modes and those of GSM MSs and UMTS UEs. 1 lists interference bottlenecks when the GU frequency separation is 2.2 MHz. 1
Interference bottleneck analysis
No.
Interference Type
BS Indicato r
MS or UE Indicator
Interference Bottleneck When the GU Frequency Separation is 2.2 MHz
1
GSM BTS interfering with the UMTS downlink
GSM BTS ACLR
UMTS UE ACS
UMTS UE ACS
2
UMTS NodeB interfering with the GSM downlink
UMTS NodeB ACLR
GSM MS ACS
No bottleneck exists because no performance loss occurs.
3
GSM MS interfering with the UMTS uplink
UMTS NodeB ACS
GSM MS ACLR
UMTS NodeB ACS**
4
UMTS UE interfering with the GSM uplink
GSM BTS ACS
UMTS UE ACLR
No bottleneck exists because no performance loss occurs.
The GU frequency separation is 2.2 MHz are obtained from an analysis of GSM BTSs, GSM MSs, UMTS BSs, and UMTS UEs.
The interference caused by a GSM MS to the UMTS uplink is limited by the ACS of the UMTS NodeB, but the simulation data shows that the adjacent-channel interference suppression is greatly improved upon filter optimization. The excessive pursuit of improvement of adjacent-channel interference suppression will result in significant loss of wanted signals. In such cases, the throughput loss in the UMTS uplink is higher than that caused by the interference from GSM MSs.
Impact of the GU/UU Small-Frequency Spacing on Network Performance For details about the impact of the UMTS non-standard bandwidth on network performance, obtain relevant documentation from MO of SRAN Solution Design Department.
1
UMTS 4.2 MHz bandwidth
GU small-frequency spacing of 2.2 MHz. The network-level GSM mean opinion score (MOS) and throughput of EDGE services decrease by less than 5% compared with those in the 5 MHz UMTS only network.
The network-level throughput of services processed by the HSDPA-enabled category 8 UEs decreases by less than 5% compared with that in the 5 MHz UMTS only network. The network-level throughput of services processed by the HSDPA-enabled category 10
UEs decreases by less than 10% compared with that in the 5 MHz UMTS only network. The figure disclosed to Indian customers is 10%.
The network-level throughput of services processed by the HSUPA-enabled category 6 UEs decreases by less than 5% compared with that in the 5 MHz UMTS only network. The figure disclosed to Indian customers is 10%.
The network-level throughput of services processed by the HSDPA+(64QAM)-enabled UEs increases by 3% compared with that of services processed by the HSDPA(16QAM)enabled UEs in the same network.
The network-level throughput of services processed by the DC(64QAM)-enabled UEs increases by 5% compared with that of services processed by the HSDPA(16QAM)enabled UEs in the same network. The gain of services processed by the 64QAM-enabled UEs is calculated compared with the 16QAMenabled UEs in the same network.
UU small-frequency spacing of 4.2 MHz
The network-level throughput of services processed by the DC(64QAM)-enabled UEs (without MIMO) increases by 6% compared with that of services processed by the DC (16QAM)-enabled UEs (without MIMO) in the same network.
The downlink peak throughput of services processed by the 16QAM-enabled UEs decreases by less than 5% compared with that in the 5 MHz UMTS only network. The network-level throughput of services processed by the 16QAM-enabled UEs decreases by less than 3% compared with that in the 5 MHz UMTS only network.
The uplink peak throughput of services processed by the UPA(QPSK)-enabled UEs decreases by less than 5% compared with that in the 5 MHz UMTS only network. The network-level throughput of services processed by the UPA(QPSK)-enabled UEs decreases by less than 3% compared with that in the 5 MHz UMTS only network
2
UMTS 3.8 MHz bandwidth in rural areas
UMTS 3.8 MHz bandwidth
In the case of GSM 1x1 or 1x3 frequency reuse pattern with FRLOAD of 50%, the network-level average rate of services processed by the HSDPA-enabled category 8 UEs decreases by 25% compared with that in the 5 MHz UMTS only network; the networklevel average rate of services processed by the DC(64 QAM)-enabled category 24 UEs decreases by 35% compared with that in the 5 MHz UMTS only network; the networklevel average rate of services processed by the HSUPA-enabled category 6 UEs decreases by 30% compared with that in the 5 MHz UMTS only network.
In the case of GSM 4x3 frequency reuse pattern, the network-level average rate of services processed by the HSDPA-enabled category 8 UEs decreases by 15% compared with that in the 5 MHz UMTS only network; the network-level average rate of services processed by the DC(64QAM)-enabled category 24 UEs decreases by 30% compared with that in the 5 MHz UMTS only network; the network-level average rate of services processed by the HSUPA-enabled category 6 UEs decreases by 18% compared with that in the 5 MHz UMTS only network.
In a 3.8 MHz UMTS network, services processed by the 64QAM-enabled UEs have no gains compared with services processed by the 16QAM-enabled UEs. 64QAM-enabled UEs can only achieve low-speed data rates of 16QAM-enabled UEs.
The network-level throughput of services processed by the DC(64QAM) UEs increases by 3% compared with that of services processed by the HSDPA(16QAM) UEs in the GUU2.0 MHz network.
Impact of the 3.8 MHz UMTS network on the GSM network: The MOS decreases by 0.15, and the coverage decreases by 0.2 dB. Assume that the antenna height is 30 meters. The coverage radius decreases by 1.3%, and the coverage area decreases by 2.58%. Although the UMTS 3.8 MHz network has a performance loss compared with the 5.0 MHz UMTS network, the 3.8 MHz UMTS network has gains compared with the 3.8 MHz GSM network. Focus on the benefits of the 3.8 MHz UMTS network when explaining it to customers. The 3.8 MHz GSM network can use the S3/3/3 cell configuration. The following table compares the gain of the 3.8 MHz UMTS network compared with the EDGE network. In this table, the peak and average EDGE data rates are calculated based on MCS-9 and MCS-6, respectively. 1
Gains provided by the 3.8 MHz UMTS network compared with the EDGE network HSDPA CAT8
HSUPA CAT6
UMTS3.8 MHz Peak rate increment compared with EDGE
252%
144%
Average rate increment of the worst cell applying UMTS3.8 MHz network compared with EDGE
418%
201%
Average rate increment of UMTS3.8 MHz network compared with EDGE
475%
245%
2 Frequency Allocation Between GSM and UMTS Networks Two frequency allocation modes are available, depending on the operator's internal spectrum resource usage: edge frequency allocation and sandwich frequency allocation. 3.2.2.1 GU Edge Frequency Allocation 1 shows the GU edge frequency allocation mode. 1
Edge GU frequency allocation mode
The UMTS and the GSM are arranged side by side on the relevant frequency band, and UMTS and GSM allocated side by side. The center frequency separation (f 1) between the UMTS and the GSM of the same operator can be configured to the minimum spacing supported by the SRAN 3.0. For the impact on the network performance, see "Impact of the GU/UU Small-Frequency Spacing on Network Performance." The center frequency separation (f 2) between the UMTS and the GSM of other operators should be 2.6 MHz at least for the following reasons: If the adjacent frequency separation between the UMTS and the GSM of another operator is lower than 2.6 MHz, the UTMS bandwidth is 4.2 MHz and but the terminal still uses a bandwidth of 5 MHz; consequently, the frequency resources of another operator are occupied. Additionally, the GU nonstandard frequency separation may interfere with the GSM because the GSM RF performance is unknown. The GSM of another operator may interfere with the UMTS either, especially when the GSM is used at BCCH frequencies or PDCH because the power control function is not enabled.
Advantages If the edge frequency allocation mode is adopted, the center frequency separation between the UMTS and the GSM of the same operator and between the UMTS and the GSM of other operators should be considered. Because of the continuous spectrum of GSM, Refarming will not increase complexity for frequency replanning. And there's no change requirement when UMTS enlarge to the second carrier in future. Generally, before the UMTS is deployed, a guard band (f) that is often one ARFCN (200 kHz) may be available between the frequency band of the operator and that of another operator. If the GU frequency separation is 2.6 MHz, Huawei SRAN 3.0 supports satisfactory network performance as if no interference exists between the GSM and the UMTS (see the interference analysis in chapter 4). In this case, the UMTS of an operator can be located adjacent to GSM carriers of another operator, the guard band included in f2, no special reservation, which will save frequency resource and improve the utilization ratio. (Note: if the guard band is a public frequency, sharing between two operators, the frequency is still remained and cannot by use by the Refarming operator.)
Disadvantages If the edge frequency allocation mode is adopted, the interference between the new UMTS and the adjacent GSM of other operators must be considered. In GU co-located sites, it is relatively easy to analyze and adjust the interference between the UMTS and the GSM. The interference between the UMTS and the GSM of other operators, however, must be considered according to the worst scenario. If the adjacent frequency is used by a CDMA system of another operator, the UMTS located at the edge, compared with the GSM at the edge, suffers severer interference from the CDMA system. For example, the blocking requirement of the GSM is –16 dBm, while that of the WCDMA system is –47 dBm. To resist the interference from the CDMA system, the system isolation is required to be improved by a higher filter suppression value or adjusted engineering parameters of the UMTS. For the edge frequency allocation, the interference between UMTS and other neighboring operator's GSM. To prevent the conflicts related to interference, the center frequency separation between UMTS and other operator's GSM should be kept 2.6 MHz at least, there are 2 frequencies can be saved at most when the flexible bandwidth feature of SRAN3.0
3.2.2.2 GU Sandwich Frequency Allocation 1 shows the GU sandwich frequency allocation mode. 1
GU Sandwich frequency allocation mode
Inside the frequency band of an operator, the UMTS is arranged in the middle and the GSM is arranged at both sides. If the center frequency separation f1 or f2 is smaller than 2.6 MHz, the GSM and the UMTS can share the frequency resources with low power density at both sides of the UMTS. In this way, the number of additional GSM carriers is twice that in the edge frequency allocation mode. In the sandwich allocation mode, the UMTS carrier can be arranged at any location (unnecessarily at the center) in the spectrum resources of the operator, depending on the operator's strategies. For later capacity expansion of the UMTS, the operator may allocate more frequencies to support two UMTS carriers. To avoid adjusting the previous UMTS frequency, asymmetric frequency allocation can be adopted to make one side of the UMTS carrier near either edge of the spectrum. In this way, the continuous GSM spectrum at the other side is larger than 5 MHz, which facilitates expansion to the second UMTS carrier. The asymmetric frequency allocation also facilitates the GSM BCCH planning. Generally, a guard ARFCN must be reserved between the BCCH and the TCH. Only one guard ARFCN is needed for the undivided BCCH frequencies. Two guard ARFCNs may be needed if the BCCH frequencies are divided into two sections. Compared with the GSM, the UMTS supports weaker resistance against interference from the CDMA system. Therefore, the UMTS carrier should be located away from the CDMA systems of other operators as far as possible to avoid interference from the CDMA systems.
Advantages For an operator, if the sandwich frequency allocation mode is adopted, the UMTS frequencies are allocated inside its own frequency resource without interference to the GSM or other systems of other operators on the adjacent frequency bands. If the reserved buffer zone is configured according to the specific requirements, normal operation of both systems is ensured. Compared with the edge allocation mode, the sandwich allocation mode supports one more ARFCN if the GU frequency separation is 2.4 MHz. The sandwich allocation mode supports two more ARFCNs if the center frequency separation is 2.2 MHz. 1 lists the comparison of KPIs between two GSM networks with the same base station (BS) configuration but different numbers of ARFCNs (one GSM network supports two more ARFCNs than the other GSM network does). The BS configuration supported by the GSM network with more ARFCNs may be higher than that supported by the other GSM network. In addition, the KPI
comparison shows that, in the case of the same BS, the GSM network with more ARFCNs has higher network performance and Refarming has less impact on the GSM network. 1 KPI comparison between two GSM networks with the same BS configuration but different numbers of ARFCNs KPI
(I) S4/3/3*
(II) S5/5/4**
5.2 MHz
5.6 MHz
7.0 MHz
7.4 MHz
Immediate Assignment Success Rate
96.16%
96.55%
96.25%
96.43%
SDCCH Drop Rate
0.69%
0.37%
0.67%
0.36%
TCH Assignment Success Rate
96.51%
96.96%
96.60%
96.81%
Call Setup Success Rate
92.80%
93.78%
92.98%
93.46%
TCH Call Drop Rate (including Handovers)
0.84%
0.49%
0.82%
0.49%
TCH Call Drop Rate
1.15%
0.72%
1.13%
0.71%
Handover RF Success Rate
94.75%
95.64%
94.93%
95.36%
In example I, the Refarming solution comes from IDEA in India. After the Refarming, the spectral bandwidth used by the GSM is 5.6 MHz. The BCCH adopts 4 x 3 and the TCH adopts 1 x 3. The typical BS configuration is S4/3/3.
In example II, the Refarming solution comes from Operator D in Country Y. After the Refarming, the spectral bandwidth used by the GSM is 7.2 MHz. The BCCH adopts 4 x 3 and the TCH adopts 1 x 3. The typical BS configuration is S5/5/4.
Disadvantages If the sandwich frequency allocation mode is adopted, both the center frequency of the UMTS and the GSM frequencies must be adjusted during the later capacity expansion of the UMTS. This problem, however, can be avoided by predetermining the location of UMTS ARFCNs according to the operators' strategies. If RF hoping is used for GSM system, the BCCH cannot be allocated continuously in the sandwich frequency allocation mode. As a result, the available MA composing of remaining frequencies is not continuous, which bring some difficulties in GSM frequency planning. 3.2.2.3 Recommended GU Frequency Allocation The sandwich frequency allocation mode is preferred for 1:1 GU co-located site scenarios according to the comparison between the two frequency allocations modes and the interference data in the case of nonstandard GU separation. The reasons are as follows: The sandwich frequency allocation mode results in severer inter-system interference, but the impact caused by the interference on the network performance is acceptable in 1:1 GU colocated site scenarios due to the improved RF counters of Huawei SRAN 3.0.
The sandwich frequency allocation mode doubles the number of GSM ARFCNs saved in the edge frequency allocation mode. Therefore, the frequency efficiency is improved and the impact on the GSM is mitigated. The inter-system interference between the UMTS and other operators′ systems must be considered in the case of edge frequency allocation but not to be considered in the case of sandwich frequency allocation. If the UMTS is adjacent to the CDMA system of another operator in the case of edge frequency allocation, the operator has to pay a high cost for suppressing the inter-system interference. In the case of sandwich frequency allocation, the UMTS ARFCN can be flexibly located to facilitate capacity expansion and inter-system interference suppression. 3.2.2.4 Frequency Allocation after the Refarming After the GU 900 MHz Refarming, the GSM frequency must be replanned. And the feature of flexible bandwidth used to minimize the influence on GSM as far as possible will bring the interference problem between the GSM900 and UMTS900. Therefore, necessary interference mitigation methods should be taken in the network planning phase. This chapter gives some suggestions from the angle of decreasing the interference between G900 and U90, and gives elaborate description for each method.
Frequency Planning for the BCCH The protocol specifies that the power control function is disabled at all timeslots of the BCCH carrier during service initiation to guarantee successful access of subscribers. The GSM ARFCN with power control disabled causes severe interference to both the uplink and the downlink of the adjacent UMTS. Therefore, the GSM ARFCN adjacent to the UMTS carrier should not be configured as a BCCH carrier. Instead, the BCCH should be deployed at a GSM ARFCN that is at least 2.6 MHz away from the UMTS ARFCN.
Frequency Planning for the PDCH In the GSM network, frequency planning of the PDCH should meet strict requirements. The PDCH is often deployed at the BCCH carrier. In the case of huge demands for data services, operators may configure an independent GPRS or EDGE carrier. In such cases, a loose frequency reuse pattern is required to mitigate interference. The PDCH does not support downlink power control, and the PDCH deployed at a GSM ARFCN adjacent to the UMTS interferes with the UMTS downlink. Therefore, the SRAN 3.0 designed for the UMTS900 R10 requires that the PDCH should not be deployed at GSM ARFCNs adjacent to the UMTS.
Interference Suppression Methods When the GSM ARFCN Adjacent to the UMTS Is Configured as the TCH Carrier If the GSM ARFCN adjacent to the UMTS is configured as the TCH carrier, the GSM power control functions must be enabled in both the uplink and the downlink to reduce the interference caused by the GSM to the UMTS. According to the statistical data of the live network, the transmit power of Huawei GSM MSs with 3.5G power control enabled is decreased by about 5 dB (compared with that of Huawei GSM MSs with third generation (3G) power control enabled). The transmit power of Huawei GSM BTSs with 3.5G power control enabled is decreased by about 3 dB (compared with that of Huawei GSM BTSs with 3G power control enabled). For details, see [15]. In this way, the interference caused by GSM MSs to UMTS BSs and that caused by GSM BSs to UMTS UEs are reduced. Other functions such as frequency hopping, DTX, and half rate (HR) can be enabled to reduce inter-system interference. When the GSM system processes the PS service, the PS
open-loop power control function must be enabled to reduce the interference between GSM900 and UMTS900.
Avoiding Non-Standard-GU-Separation ARFCNs in the Same Cell in the Case of Sandwich Frequency Allocation If the sandwich frequency allocation mode is adopted, GSM ARFCNs adjacent to the UMTS appear in pairs. If several GSM ARFCNs adjacent to the UMTS are configured in the same cell, the cell is more easily interfered by the UMTS. As a result, the performance of the cell is much lower than that of other cells. In addition, the UMTS cell sharing the same coverage with the GSM cell is severely interfered. If the GSM ARFCNs adjacent to the UMTS are distributed in different cells, the mutual interference between the GSM and the UMTS can be equalized. Therefore, GSM ARFCNs adjacent to the UMTS should be separated geographically to equalize the network quality and to avoid poor performance (much poorer than the overall network performance) in one or two cells due to severe interference.
Frequencies with Nonstandard Separation Not Used in Indoor GSM Cells UMTS900 can be used for deep coverage in urban areas, that is, the macro base station covers is used for indoor coverage. Generally, GSM900 uses a special indoor coverage solution. If the frequencies with nonstandard separation are used for GSM indoor coverage, the GSM indoor base station may cause interference to UMTS terminals. The UMTS terminal located in the GSM indoor coverage area receives rather weak signals because the signal strength decreases significantly after penetrating the building and distributing in indoor environment. However, there is no attenuation for GSM signals dedicated for indoor areas. Therefore, the UMTS terminal receives rather strong GSM signals. In this case, GSM frequencies with nonstandard separation may cause great impacts on the UMTS terminal. To avoid the serious impacts, it is recommended that frequencies with nonstandard separation should not be used in indoor GSM cells.
1
Coverage of indoor GSM cells
Frequencies with Nonstandard Separation Not Used in Cells Requiring Large UMTS Capacity To reach a high data throughput, the UMTS system must use a high-order modulation coding scheme, for example, HSDPA using 16QAM using or HSDPA+ using 64QAM. The high-order coding scheme requires high-quality signals and is more sensitive to interference signals. According to the performance tests of the GU frequencies with nonstandard separation in the lab, the small-spacing frequencies bring greater impacts on high coding rates. Assume that the transmit power of the GSM system and UMTS
system is 20 W. When the channel quality indicator (CQI) is 30 in edge allocation mode, the GU performance loss of 64QAM is 30% to 40% in GU co-site deployment scenario. In the actual network, the UMTS cells require different capacities in the same area because the uses are not evenly distributed in cells. To mitigate the impacts of the GU frequencies with nonstandard separation on data throughput of the entire UMTS system, it is recommended that frequencies with nonstandard separation should not be used in cells with a high UMTS capacity during the GSM frequency planning. Enabling the HSUPA algorithm for resisting strong interference can relieve the impacts of instantaneous GSM interference to UMTS performance.
Enabling the HSUPA Algorithm for Resisting Strong Instantaneous Interference from GSM (Optional) The power control function is not enabled during the access of GSM terminals. In the case of the access to the TRX using frequencies with nonstandard separation, GSM terminals transmit signals at full power, greatly increasing the uplink background noise of neighboring UMTS cells. The common scheduling algorithm of the UMTS system uses the uplink load as the control threshold and measures the upload through Received Total Wideband Power (RTWP). If the RTWP is raised to a specified load threshold, the UMTS system will control the HSUPA scheduling rate and limit the uplink load within the threshold. The great increase in RTWP of the UMTS system seriously affects the uplink service rate of the UMTS system and leads to poor user experience. The HSUPA algorithm for resisting strong interference differentiates instantaneous interference causes by interference of other external systems for example, GSM. When there is strong interference and the RTWP increases drastically, the scheduling algorithm checks the RTWP and the load factor contributed by users in the local cell. If the load factor does not reach the predefined threshold, the user rate can be increased even if the RTWP exceeds the threshold. Therefore, if GU frequencies with nonstandard separation are used, enabling the HSUPA algorithm for resisting strong interference can greatly relieve the impacts of instantaneous strong interference of GSM users on the overall UMTS performance. Based on lab testing results, the maximum continuous interference supported by the HSUPA algorithm for resisting interference is 17 dB. If the continuous interference is larger than 17 dB, the HSUPA algorithm for resisting interference is not functional. This algorithm is applicable to RAN13, SRAN6.0 or later, not supported by SRAN3.0. In addition, because this algorithm is not verified, you are advised to confirm with the SRAN Solution Design Department first before using this feature.
3 GU Intra-Frequency Buffer Zone Planning This section provides only a simple description about the concept, principles, and solution of the buffer zone planning. For more details, see the GU Refarming Bufferzone Solution.
3.2.3.1 Definition Some frequencies used by the UMTS network in the Refarming area are still used by the GSM network outside the Refarming area. As a result, co-channel interference between the GSM and UMTS network may occur at the Refarming area edge. For more details, see reference [1]. A buffer zone can be established to reduce such interference. As shown in 1, the same frequency can be used in Area A (UMTS900) and Area C while frequencies used in Area A cannot be used in Area B, which is called the buffer zone.
1
Buffer zone
The area where UMTS900 is deployed and the buffer zone that implement frequency replanning are called Refarming area. To ensure that the GSM900 sites where Refarming is not implemented are not affected, the frequency of some sites outside the Refarming area may be adjusted. Therefore, the actual frequency replanning area is larger than the defined Refarming area.
Theoretical Analysis The modeling of theoretical interference analysis is shown in 1. The seven sites in the two layers at the center are BTSs. The outmost layer indicates the GU co-located sites. Layers 3 and 4 indicate the buffer zone where the GSM frequencies shared by the UMTS must be cleared (Clearing frequencies means not use). 1
Modeling of theoretical interference analysis
The theoretical analysis is performed based on the coverage analysis using appropriate propagation model and considering the particular service requirements. The theoretical analysis shows that the interference is acceptable for 3-sector BSs if two layers of GSM BTSs whose frequencies are shared by the UMTS are cleared. For details, see reference [16]. The theoretical analysis in reference [16] is based on the standard network structure which may differ from actual network conditions. Therefore, the impact caused by the interference varies with actual network conditions — for example, propagation loss that varies with terrains and ground features, parameter settings, cell size, and cell location. The degraded network quality in one or two BSs can be optimized through adjustment of RF parameters. In addition, the theoretical derivation in reference [16] is based on BSs with directional antennas. For BSs with omnidirectional antennas, a larger buffer zone may be required because the coverage is hard to control. The simulation is based on the regular network structure. The following conclusions are drawn according to the simulation data:
Assume that the C/I is 12 dB and that the acceptable coverage loss due to co-channel interference is within 3%. Two layers of GSM BTSs whose frequencies are shared by the UMTS must be cleared. In the case of GSM 4 x 3 frequency reuse pattern, while three layers of GSM BTSs must be cleared in the case of GSM 3 x 3 frequency reuse pattern.
Assume that the C/I is 9 dB and that the acceptable coverage loss due to co-channel interference is within 3%. Two layers of GSM BTSs must be cleared in the case of either GSM 4 x 3 or 3 x 3 frequency reuse pattern.
A tighter GSM frequency reuse pattern results in severer self-interference and greater influence from the UMTS, requiring a larger buffer zone between the GSM and the UMTS.
3.2.3.2 Buffer Zone Planning and Application Scenarios Currently, buffer zone can be planned through simulation, traffic statistics, and original Measurement Reports (MRs). Each planning method has its own advantages and disadvantages. 1 shows the comparison. 1
Comparison of the three methods for buffer zone planning Based on Simulation
Based on Traffic Statistics
Based on Original MRs
Principles
Defining the buffer zone by using U-Net to predict coverage based on the pre-set receive level
Defining the buffer zone based on the counters and engineering parameters in the live network
Defining the buffer zone based on the original MRs and engineering parameters in the live network
Data Input
Detailed engineering parameters, data map, and parameters in the live network
Detailed engineering parameters and counters
Detailed engineering parameters and original MRs
Application Scenarios
All Scenarios
Scenarios where equipment is provided by Huawei or any vendor except for ZTE
Scenarios where equipment is provided by Huawei
Based on Simulation
Based on Traffic Statistics
Based on Original MRs
Accuracy
Low, not considering the traffic distribution in the live network
High, considering the traffic distribution in the live network
High
Complexity
Simple, requiring knowledge about the U-Net
Simple, having low requirement on skills of using tools
Complex, requiring the use of professional tools in automatically analyzing large quantities of MR data
Maturity
Mature, with detailed case verification
Mature, with detailed case verification
Immature, not fully verified
Advantages
Applied to all scenarios
Easy to implement with high accuracy
With high accuracy
Disadvantages
With low accuracy which relies on the accuracy of digital maps and engineering parameters
Cannot be implemented in the ZTE network and takes one week to obtain relevant data in the live network
Difficult to obtain and analyze the required data
Different methods of buffer zone planning apply to different scenarios. Planning based on traffic statistics is recommended. If relevant traffic statistics cannot be obtained or the vendor's traffic statistics cannot be analyzed by Actix, the planning based on simulation is recommended. Do not use the planning based on the original MRs unless required by the frontline personnel or operators.
4 GUL Inter_Rat Mobility Solution This section introduces the GUL inter-RAT mobility solution. For more details, see the GUL Inter-Rat Mobility Solution.
The general solution is as follows: A multi-mode cell phone preferentially camps and initiates a service in a network with a higher priority. By default, the LTE has higher priority than the UMTS and the GSM has the lowest priority.
CS Services 1)
The GSM or UMTS network carries CS services initiated by camping terminals. A terminal initiating a CS service in the UMTS network can be handed over to the GSM network based on coverage and this CS service will not be handed over back to the GSM network when the call is proceeding.
2)
When IMS is not deployed in the LTE network, CS services need to be transferred to the UMTS network by CS Fallback (CSFB).
3)
When IMS is deployed in the LTE network, the Single Radio Voice Call Continuity (SRVCC) feature works to convert the VoIP services in the LTE network to CS services in the UMTS network. This ensures continuous voice services.
PS Services
1
1)
PS services of LTE terminals are preferentially carried by the LTE network. When a UE in the middle of a PS service in the LTE network moves out of the LTE coverage, a PS handover or re-direction will be performed to transfer the UE to the UMTS network or the GSM network (if the UE moves out of the UMTS coverage.) The choice between a PS re-selection and a PS handover depends on the capability of the UE.
2)
PS services of GU dual-mode terminals are preferentially carried by the UMTS network. When a UE in the middle of a PS service in the UMTS network moves out of the UMTS coverage, a PS re-selection or handover will be performed to transfer the UE to the GSM network.
3)
When a multi-mode terminal in connected mode moves back to an area covered by multiple RATs, the terminal will not fall back to the LTE network since the terminal cannot measure the signal quality of the LTE neighboring cells. Instead, PS reselections or handovers will be performed between the GSM and UMTS networks. After the CS service is released, the terminal will fall back to the LTE network through re-selection.
Combined Services 1)
The policy for CS services applies to the traffic transfer from the UMTS network to the GSM network. Service-based handovers will not be performed for combined services.
2)
For combined services, traffic needs to be transferred from the LTE network to the UMTS or GSM network only if a CS service is initiated while a PS service is performed in the LTE network. In this case, the CSFB feature is enabled on the base station.
GUL inter-Rat mobility strategy
5 GSM Traffic Transfer Solution This section provides only a general introduction to the GSM traffic transfer policy. For more details, see the GU Refarming traffic migration Guide.
The GSM frequency resources are reduced after the GU 900 MHz Refarming is implemented. To keep the GSM network quality, the cell configuration in the GSM network must be changed. Due to the low penetration rate of UMTS900 terminals or other factors, the GSM traffic volume may not decrease fast within a period after the Refarming. The following methods can be adopted to prevent the GSM network performance from deteriorating and keep the frequency reuse coefficient without causing traffic congestion: Improving efficiency of TRXs Transferring GSM900 traffic to another RAT 3.2.5.1 Configuration Goal of the GSM900 Network The goal is to implement the maximum average cell configuration based on the available GSM 900 MHz resources and the frequency reuse coefficient after the Refarming. If it is promised that KPIs do not deteriorate after the Refarming, the frequency reuse coefficient must remain the same. Otherwise, you have to assess the network performance deterioration caused by tightening of the coefficient. The assessment must be reviewed by Huawei KPI Auditing committee through the exceptional KPI auditing process.
Allocating frequencies to BCCHs and TCHs separately In this case, BCCHs and TCHs have different frequency reuse coefficients. Assume that the frequency reuse coefficient for BCCHs is X*3, that for TCHs is Y*3, and the available bandwidth is W MHz. The maximum average cell configuration is as follows:
−
AverageCellTrxNum = (Rounddown ((W/0.2),0)-X*3)/(Y*3) + 1 if the frequency hopping mode of TCHs is None FH or Baseband FH
−
AverageCellTrxNum = Rounddown ((Rounddown((W/0.2),0)-X*3)/(Y*3)/2) + 1 if the frequency hopping mode of TCHs is RF FH
Allocating frequencies to BCCHs and TCHs combinedly In this case, BCCHs and TCHs have the same frequency reuse coefficient. Assume that the frequency reuse coefficient is Z*3, the available band width is W MHz. The maximum average cell configuration is as follows: AverageCellTrxNum = Rounddown ((W/0.2),0)/(Z * 3) Rounddown ((W/0.2),0) in the preceding equation indicates the number of available GSM frequencies after the Refarming. If there are any dedicated frequencies in the network (for example, dedicated frequencies for indoor coverage or EDGE TRXs), the number of such frequencies should be excluded from the result.
Methods of Traffic Migration Increasing the half-rate service proportion 1
This is the simplest method. The proportion can be as high as 100% with the customer's permission. To increase this proportion, decrease the values of the TCH traffic busy threshold, AMR TCH/H Prior Cell Load Threshold, and Max Ratio of AMR-HR parameters.
2
Transferring the GSM900 traffic to the UMTS900 or UMTS2100 network
The volume of GSM900 traffic that can be transferred to the UMTS network can be calculated based on the penetration rate of UMTS900 terminals mentioned in section . Besides, more GSM900 traffic can be transferred to the UMTS network by modifying the traffic carrying policy between GSM and UMTS networks as well as the corresponding parameters. 3
Transferring the GSM900 traffic to the GSM1800 network The GSM1800 network cannot absorb all the GSM900 traffic due to its relatively weak coverage. The maximum GSM900 traffic that can be absorbed by the GSM1800 network is determined by the proportion of GSM900 traffic that can be transferred to the GSM1800 network. To transfer GSM900 traffic to the GSM1800 network, do as follows: 1)
Obtain the value for the Rx level distribution of the GSM900 cells.
2)
Calculate the proportion of GSM traffic that meets the inter-layer handover requirement based on the preceding Rx level and HO signal level threshold from G900 to G1800. This proportion is equal to the proportion of GSM900 traffic that can be absorbed by the GSM1800 network.
3)
Change the layer HO threshold or HO signal level between overlaid layer and underlaid layer as needed. This method involves the GSM1800 network deployment and expansion, which is the key to successful Refarmings. Before the Refarming, inform the customer about relevant materials to be prepared and configurations to be made in the live network. Besides, the GSM900 traffic can be transferred to the GSM1800 network by splitting cells or adding indoor base stations, base stations in streets, Micro base stations, and Pico base stations.
4
Enabling the tight frequency reuse features If the GSM900 TRX configuration cannot be changed as required, the following GSM features can be enabled to keep the GSM network quality:
Frequency Hopping (RF hopping): changing the frequency reuse method to enhance the supported TRX configurations
ICC, EICC, and SAIC: improving the anti-interference capability of the network to enhance the supported TRX configurations
VAMOS: improving the TRX usage
UISS+IBCA: improving network quality when the Frequency Hopping (RF hopping) feature is enabled and the FRLOAD is higher than 50%, enhancing the supported cell configurations without requiring more frequency resources The GSM900 network performance quality cannot be kept only by enabling the tight frequency reuse features. The most effective way is to transfer the GSM900 traffic to the expanded or newly deployed GSM1800 network.
3 Implementation 1 Delivery Solutions Currently, there are two scenarios: Refarming for base stations provided by Huawei and Swapping&Refarming for base stations provided by other vendors. For the first scenario, skip this section.
For the second scenario, there are two delivery solutions. Delivery solution 1 The delivery process of this Refarming solution is as follows: 1
Replan the GSM900 network and frequencies on the live network to ensure the frequencies required by the UMTS900 are idle.
2
Monitor KPIs of the GSM900 network for one or two weeks. If the KPIs are greatly affected, it is recommended that the RF optimization be performed on the GSM900 network. If the impacts on KPIs are acceptable, swap the GSM900 network.
3
After the KPIs of the GSM900 are stable, activate the UMTS900. The advantages of this Refarming delivery solution are as follows: Separate the two factors affecting the networking performance and divide the network performance optimization process into two stages: (1) Impact on the GSM network performance when the frequency spectrum is changed from tight to loose. (2) Impact of the interference between the GSM900 and UMTS900 on the network performance after the UMTS900 network is activated. This helps to analyze and identify the causes affecting KPIs. If the GSM network performance is reduced after the Refarming is implemented on the equipment provided by other manufacturers, it indicates that this problem is a common phenomenon and is not caused by the swap to Huawei equipment. In this way, the early stage of Refarming can be smoothly implemented. The first stage of this solution, however, is risky. If the GSM network performance is substantially reduced after frequency replanning, operators may question the feasibility of Refarming and the network swapping may be affected. If operators or third parties perform the frequency replanning based on the existing equipment, the frequency replanning may not meet the requirements of the GSM900 network after Refarming served by Huawei equipment, especially when ARFCNs with nonstandard frequency separation are used and some special network planning strategies for optimal network performance are used. In this case, the frequency replanning must be adjusted again. In addition, the frequency replanning based on the existing equipment may affect the usage of Huawei equipment. For example, the existing equipment adopts the baseband FH mode to use the cavity combiner. Therefore, the baseband HF mode must remain unchanged during network swapping. That is, the RF FH mode cannot be used, affecting the optimization of network performance. If Huawei performs the frequency replanning based on the existing equipment, the KPI requirements of the network after Refarming may not be met because Huawei is not familiar with the performance of the existing equipment and the related algorithm. In this case, with respect to delivery solution 1, it is recommended that you promise that the GSM KPIs remain unchanged after the UMTS900 network is activated.
Delivery solution 2 The delivery process of this Refarming solution is as follows: 1
Swap the GSM network according to 1:1.
2
Customers check and accept the GSM swapping.
3
Communicate with customers about the UMTS900 Refarming on the basis that the frequency replanning is sold to customers as a service.
4
Sell the UMTS900 license to customers and activate the UMTS900 network. This Refarming delivery solution features little risk. Huawei can determine the methods for improving the network quality because Huawei performs the network swapping and frequency replanning again. This increases the flexibility of network optimization. In addition, Huawei deserves the extra service cost and license cost involved in the
subsequent frequency replanning from operators. The standard for promising KPIs in this delivery solution, however, is not as clear as that in delivery solution 1. In this case, ensure that you warn customers in advance about the decline in performance due to GSM tight frequency reuse in large configuration scenarios. In addition, the process of KPI optimization of delivery solution 2 is more complicated than that of delivery solution 1. Delivery solution 2 has another type, which does not require the network acceptance after the GSM network swapping. Instead, the network is checked and accepted after the entire project is completed. In this way, the GSM network can be adjusted again after the UMTS900 network is activated. In common delivery solution 2, however, to ensure the KPIs of the GSM network after acceptance, the GSM network cannot be adjusted again after the UMTS900 network is activated. In this case, if the co-antenna solution is adopted, the RF parameters and other parameters must be adjusted according to the performance of the UMTS900 and GSM900 networks, affecting the original KPIs of the GSM network. The delivery solution where the KPIs are checked and accepted after the entire project is complete is more flexible. Specifically, after the UMTS900 network is activated, the GSM network can still be adjusted as long as the ultimate KPIs are ensured. Table 3.1.2.I.1.2.1.1 Comparison between UMTS900 Refarming delivery solutions 1 and 2 Solution 1 Solution descripti on
Replan the GSM900 network and frequencies on the live network to ensure the frequencies required by the UMTS900 are idle. Monitor KPIs of the GSM900 network for one or two weeks and determine the performance baseline after frequency replanning. If the KPIs are greatly affected, it is recommended that the RF optimization be performed on the GSM900 network.
Solution 2
Problem: How to charge for frequency replanning and RF optimization?
Swap the GSM900 network. Activate the UMTS900 network if the KPIs of the GSM900 are normal.
Swap the GSM network according to 1:1. Customers check and accept the GSM swapping (signing the PAC is recommended). After that, sell the frequency replanning of the UMTS900 network Refarming to customers as a service. Replan the frequencies of the GSM network to ensure that the frequencies required by the UMTS900 are idle. Whether to adopt solution (2) or solution (2') depends on the result of negotiation.
Activate the UMTS900 network after the frequency replanning is complete.
Solution 1 Solution advanta ges
The performance of the GSM network after Refarming is degraded. The performance comparison baseline before and after the network swapping, facilitating the ultimate acceptance of the network quality.
Solution 2
You can work around the potential risks due to the frequency replanning based on the equipment from the third party before Refarming. Customers can flexibly deploy the network and do not need to implement the Refarming before the network swapping. In addition, the frequencies are not required before the UMTS network is deployed. The frequency replanning is facilitated and is more suitable for Huawei Refarming solution.
Based on the analysis of solutions described in Table 3.1.2.I.1.2.1.1, the following network swapping strategies for Refarming scenarios are recommended. Solution 1 is recommended for Golden Cluster, and solution 2 is recommended for project swapping.
2 Implementation Procedures The following figure shows the implementation flowchart.
Figure 3.1.2.I.1.2.2 Implementation flowchart
The detailed procedures are as follows: 1
Make the configuration plan for cells in the GSM900 and GSM1800 networks based on the Refarming policy.
2
Expand the GSM1800 network or deploy a new GSM1800 network and gradually transfer GSM900 traffic to the GSM1800 network based on the specific solution in section 2.
3
Make the following GSM900 frequency re-planning solutions: −
GSM900 TRXs whose sectors are reduced use the UMTS900 frequencies after the Refarming.
−
GSM900 TRXs whose sectors are maintained use the GSM frequencies after the Refarming.
4
Implement the GSM900 frequency re-planning solution.
5
Deactivate GSM900 TRXs whose sectors are reduced and then activate the UMTS900 TRXs. The following figure shows the implementation procedures for the SFR project in France.
1
Implementation procedures for the SFR project in France
2 Network Optimization and Acceptance 1 Network Optimization After 900 MHz Refarming, the decrease in frequency resources may cause serious impacts on GSM network. To ensure network quality, you must replan and optimize the GSM network in four aspects: performance and algorithm, basic network optimization, equipment and engineering, and network architecture. As shown in 1Error: Reference source not found, the four optimization aspects form a pyramid and the importance increases from the top to the bottom. The adjustment in the network architecture is the basis for solution implementation. The network optimization cannot be depending only on one or several algorithms.
1
GSM network optimization
Performance Algorithm Basic Network Optimization
Equipment and Engineering
Network Architecture
After the Refarming, the main problems for the GSM network are abnormal KPIs, such as antenna connections, interference band, call drops, and voice quality. Troubleshoot these problems by referring to the Refarming X Action and GSM Performance Optimization X Action.
2 GSM Network Acceptance After the Refarming, perform GSM network acceptance as required by the contract. No special acceptance tests are required.
2
UMTS Part
1 Network Assessment 1 Assessment and Analysis of KPIs 1
Collecting KPIs of the live network The following table shows the KPIs that need to be collected.
1
UMTS network KPIs
2
KPIs Assessment for the UMTS900 Network Generally speaking, KPIs of the UMTS900 network are worse than those of the UMTS2100 network. For the UMTS acceptance, use the UMTS900+UMTS2100 KPIs after the Refarming to compare with the UMTS2100 KPIs before the Refarming. For details about UMTS900 KPIs, see the KPI Influence of U900 Network.
2 UMTS900 Coverage/Capacity Assessment U-Net can be used to provide a simple report on the UMTS900 coverage performance assessment. Since this assessment can neither bring many gains to solution design and implementation nor be sold as a service, implement this assessment only when customers have strong demands. If the customer requires a detailed report, the GU Refarming assessment service introduced in SingleRAN 7.0 can be provided. There are two scenarios for this service: one is in blind or weak UMTS coverage areas, the other is in UMTS capacity limited areas.
If the potential Refarming area has blind or weak UMTS coverage, give suggestions to customers after doing the following: 1)
Identify areas with blind or weak UMTS coverage by using the tool for accessing GSM and UMTS coverage.
2)
Assume that the service model of UMTS900 terminals and that of GSM terminals are the same. Calculate the GSM900 PS traffic that can be transferred based on the penetration rate of UMTS900 terminals. If most of the UMTS900 terminals are data cards, the transferred data traffic can be increased accordingly.
3)
Calculate the GSM CS traffic that requires to be transferred based on the penetration rate of UMTS900 terminals. Then provide the GSM1800 traffic transfer solution by referring to the Refarming Traffic Migration Guide and make the GSM configuration planning for the Refarming.
If the potential Refarming area has UMTS capacity limitation, suggest to customers after doing the following: 1)
Identify the value areas for the Refarming based on the UMTS2100 traffic.
2)
Assume that the service model of UMTS900 terminals and that of UMTS2100 only terminals are the same. Calculate the data traffic that can be transferred to the UMTS900 network based on the penetration rate of UMTS900 terminals.
3)
Then provide the GSM1800 traffic transfer solution by referring to the Refarming Traffic Migration Guide and make the GSM configuration planning for the Refarming.
This assessment only applies to the network using Huawei equipment of versions later than SRAN7.0 because the traffic map and UMTS900 terminal penetration rate are based on Huawei GSM and UMTS equipment and only Huawei equipment of versions later than SRAN7.0 support identifying UMTS900 terminals. For more details, see the Technical Guide of the SRAN7.0 GU Refarming Evaluation Service.
3 Identifying UMTS Value Areas On U-Net, enable the GU Joint Coverage Plan function to identify the value areas for Refarming. The value areas are identified based on the area priority order. The default priority order is UMTS blind zones > Zones with weak UMTS and GSM > Zones with weak UMTS and strong GSM. When you identify value areas, try to select sites near to each other.
BTS
BTS NodeB
2 Solution Planning MBTS
1 Antenna Solutions
BTS BTS 4.2.1.1 Principles
SASU
In the Refarming scenario, the UMTS system is built on the basis of the existing GSM system. In this case, the reuse of the existing antenna system can reduce the network construction cost of operators; however, the impact of the co-antenna system on the performance of the GSM and UMTS systems should be considered. The common antenna solutions in the GU co-located scenario are as follows: GSM/UMTS separate antenna, GU four-port co-antenna, and GU two-port co-antenna. In the scenario of SRAN deployment based on the software designed radio (SDR) technology, generally, only the co-antenna solution can be used because the GSM and UMTS signals are combined into one output. In some special cases, however, the separate antenna solution can be adopted because the SRAN can be configured in either GSM only mode or UMTS only mode. In the non-SRAN deployment scenario, either the co-antenna or separate antenna solution can be adopted according to actual network conditions and operator requirements. 1
GU separate antenna
Antenna Solutions
GU four-port co-antenna
GU two-port co-antenna
1 shows different antenna solutions with the macro BTSs as examples. These solutions also apply to distributed base stations (DBSs) regardless of the product type. When the two-port co-antenna solution is adopted, the combiner is required only if the non-SRAN is deployed. 1 shows both the SRAN and non-SRAN adopting the co-antenna solution (The co-frequency combiner used by the non-SRAN is SASU.) 1 shows the comparison among different antenna solutions.
1
Comparison among different antenna solutions
Antenna Solutions
Antenna Space
Cost
Performance
Implementation
O&M
GU separate antenna
A lot of space is required.
Additional feeders, antennas, and poles are required, increasing the network construction costs.
Azimuth angle, electronic tilt, and mechanical downtilt can all be modified independently, leaving little impact on the GSM and UMTS network performance.
It's difficult to implement since new antennas, feeders, and poles are required.
The azimuths and tilts of GSM and UMTS networks can be modified independently.
The number of antennas is increased, which easily attracts attentions.
GU four-port co-antenna
Additional supports and poles are not needed, saving space.
New four-port antennas and feeders are required, increasing cost. However, this solution saves rent and equipment cost because additional supports and poles are not required.
The electronic tilt can be modified independently. However, the GSM and UMTS azimuth angle must be consistent.
Replace the twoport co-antenna with the fourport one and add new feeders. The number of antennas is reduced.
The azimuths of GSM and UMTS networks must be consistent.
GU two-port co-antenna
Additional supports and poles are not needed, saving space.
This solution saves costs and reduces workload during construction because the original antennas and feeders can be reused. This solution also saves rent and equipment cost because additional supports and poles are not required.
The GSM and UMTS antenna engineering parameters must be consistent, impacting network performance.
You do not need to add antennas, feeders, or poles. The number of antennas is reduced.
The azimuths and tilts of GSM and UMTS networks must be consistent.
In summary, the main advantage of solution 1 is that engineering parameters of the GSM and UMTS systems can be adjusted independently, and the performance of the GSM and UMTS systems is not affected. The main disadvantage is that the cost of network construction is
increased. On the contrary, the main advantage of solution 3 is that the cost of network construction is reduced. The main disadvantage is that engineering parameters of the GSM and UMTS systems cannot be independently adjusted, and the network performance and subsequent network optimization are affected. The advantage and disadvantage of solution 2 are somewhere in between of those of solution 1 and solution 3. The co-antenna solution affects the performance of the GSM and UMTS systems to some extent. Therefore, the impact on the performance is factored to determine whether co-antenna solution is adopted. The following sections evaluate the impacts of co-antenna on the performance in different scenarios based on the simulation of engineering parameters on the live network. 4.2.1.2 Impact on Network Performance The impact of co-antenna adoption on network performance is as follows:
For rural areas, the site distance is large and the traffic volume is small. After the Refarming, the UMTS can use the antenna engineering parameters of the legacy GSM network, causing little impact on UMTS network performance.
For urban areas, the site distance is small and the traffic volume is high. To reduce interference, the downtilt is usually set to a large value. If the downtilt of the existing GSM system is too large (such as 2º to 3º), site distance is too small (less than 200 m), azimuth angle is not standard (less than 90º), and there are extra-high sites (higher than 45 m), coverage overlap will occur, causing serious interference which affects UMTS network performance seriously. To decide whether to adopt the co-antenna solution, check whether the downtilt, ISD, azimuth angle, and site height of the legacy network are appropriate. Otherwise, optimize the RF of the legacy network. The impact of two-port co-antenna adoption on network performance is as follows:
For rural areas, the average throughput loss is smaller than 5% and the cell edge throughput loss is smaller than 10%. The reason is that in rural areas, the traffic is small and the site distance is large. In addition, if BTSs and NodeBs share all the sites, the UMTS can use the engineering parameters of the legacy GSM network, causing little impact on UMTS network performance.
For urban areas, the downtilt is set to a large value. The reason is that traffic load is heavy and the site distance is small. If the engineering parameters are appropriate, the average throughput loss is smaller than 5% and the cell edge throughput loss is smaller than 10% when the BTSs and NodeBs share all the sites. Otherwise, optimize the RF of the legacy network.
4.2.1.3 Antenna Application Policy in Urban Areas
Scenario of GSM Swap and UMTS Swap The antenna solution used before Refarming is adopted. That is, if GU co-antenna solution is used before the Refarming, the GU co-antenna solution is still used after the Refarming. The engineering parameters are not changed. If GU independent antenna solution is used before the Refarming the GU independent antenna solution is still used after the Refarming. The engineering parameters keep consistent with that before the Refarming.
Scenario of GSM Swap and UMTS Establishment Based on the consideration of the affect on performance, maintenance, and optimization, you are advised to use the independent antenna solution.
The co-antenna solution in which the co-antenna solution serves as the major solution with some independent antennas deployed is cost-effective. For the cells where co-antenna solution is used, certain optimization methods can be implemented to further improve the performance. 4.2.1.4 Antenna Solution Optimization The co-antenna solution does not apply to the following scenarios: Pole space limited scenario: One operator may own multiple network systems. These network systems may share one pole in some cells, or the network systems of two operators share one pole. In this case, there may not be sufficient space on the pole for the installation of the UMTS antenna. At the site, however, the addition of another pole is not allowed. Therefore, the UMTS network must share the antenna with the original GSM network. Similar to the space limitation scenario, the four-port co-antenna solution is preferentially adopted. The azimuth angle of the four-port antenna is set according to the azimuth angle of the existing GSM network, the GSM down tilt angle is set according to the down tilt angle of the live network, and the UMTS down tilt angel is set according to the network planning. Tower top bearing limitation scenario: In the actual project construction, the bearing capability of the space or tower top may be limited. In this case, the two-port co-antenna solution must be adopted to reduce the bearing of the space and tower, and the security is ensured. High GSM site scenarios: During the earlier stage of GSM network construction, some high sites are established to perform broad coverage due to the lack of sites. When frequency planning is performed, a group of independent ARFCNs are used for these high sites to avoid frequency interference because the coverage scale is large. For the UMTS which frequency reuse pattern is 1, the high sites usually lead to interference. This greatly affects the network performance. For example, if the average antenna height is 30 m, an antenna of 45 m is a high site, cross coverage and pilot pollution may occur. In practice, the high sites can be determined by U-Net simulation, average height of building, and antenna height. For high sites, the antenna height must be lowered by adopting the independent antenna (if no negative effect is brought when GSM antenna height is lowered, co-antenna can be implemented after the antenna height is lowered), or disable the UMTS on the site. The azimuth angle is smaller than 90°: When the azimuth angle is smaller than 90°, the number of overlapped areas between cells increases. In the UMTS which frequency reuse is 1, mover overlapped areas indicate more interference. For GSM cells, a looser frequency reuse pattern is used. Adjacent cells use different frequencies; therefore, frequency planning can be implemented to mitigate interference. In this way, the engineering parameters of GSM cells which azimuth angle is smaller than 90° are not applicable to the UMTS on the live network. For these cells, GMS/UMTS separate antenna can be configured to control the number of overlapped areas of two cells. If the azimuth angle of a cell is too small due to capacity reason, another cell can be disabled, and the coverage can be completed by using the U2100. The distance between sites is small: If the distance between sites is small, different ARFCNs are configured for adjacent GSM cells to mitigate interference. However, for UMTS cells, small distance between sites may cause pilot pollution. The coverage of these cells must be strictly controlled by configuring separate antenna, or by disabling some sites on the premise that the coverage is not affected. When co-antenna is used, the following methods can be adopted to further improve the UMTS network performance. 1
UMTS power optimization In a cell where interference is severe, the pilot power can be reduced to control the cell coverage and alleviate the interference between cells. The antenna does not need to be
adjusted and this operation does not affect the GSM performance while increasing the UMTS network performance. 2
Control of down tilt angle in cells In a cell where the down tilt angle causes stronger interference to the network performance, the down tilt angle of antenna can be adjusted to reduce the interference between UMTS cells. The adjustment of antenna affects the coverage of GSM. The GSM carrier power can be optimized to reduce or avoid the impact on GSM performance. Another option is to configure four-port co-antenna. In this way, the down tilt angle can be independently adjusted. The GSM performance is not affected and the UMTS performance is ensured. However, antenna cost and module cost must be increased.
3
Azimuth angle adjustment In a cell where the azimuth angle causes stronger interference to the network performance, the azimuth angel of antenna can be adjusted by configuring UMTS independent antenna. In this way, the interference between UMTS cells is reduced. However, the antenna cost and module cost are increased because a pair of antennas and modules must be added.
2 UMTS Inter-Carrier Mobility Solution 1
Idle Mode Idle UEs support bidirectional cell reselection between UMTS and GSM and camp on UMTS900 or UMTS2100 cells randomly. For areas co-covered by UMTS2100 and UMTS900 cells, the Qqualmin/Qrxlevmin or Offset from U900 to U2100 parameter can be configured to change the number of UEs in idle mode.
2
CS Connected Mode In the UMTS900 central area, when a UE initiates a CS service in the UMTS2100 network and moves out of the UMTS2100 coverage, the UE will be handed over to the UMTS900 or GSM network based on coverage. A UMTS900 cell cannot be configured as the neighboring cell of a UMTS2100 cell or a GSM cell. In the UMTS900 area edge, a UE can be handed over between the UMTS900 network and the UMTS2100 or GSM900 network based on coverage.
3
PS Connected Mode In the UMTS900 central area, when a UE initiates a PS service in the UMTS2100 network and moves out of the UMTS2100 coverage, the UE will be handed over to the UMTS900 or GSM network based on coverage. A UMTS900 cell cannot be configured as the neighboring cell of a UMTS2100 cell or a GSM cell. In the UMTS900 area edge, a UE can be handed over between the UMTS900 network and the UMTS2100 or GSM900 network based on coverage. Different operators have different quantity of UMTS2100 carriers as well as different UMTS2100 inter-carrier mobility solutions. The Refarming solution should not affect the existing UMTS2100 inter-carrier mobility solution.
3 Power Configuration Analysis By default, transmit power at the top of the cabinet in the UMTS900 network is 20 W. When the transmit power at the top of the cabinet in a co-sited GSM900 network is larger than 20 W, set the transmit power in the UMTS900 network to be the same as that in the GSM900 network. After the Refarming, not only the carrier configuration but also the power configuration should meet the RF module requirements. If the current power configuration cannot meet the
RF module requirements, the GSM or UMTS power configuration should be modified or new RF modules should be added. 1 lists the typical carrier power configuration for the RRU3908 V2 module. 1
Typical carrier power configuration for the RRU3908 V2 module Numbe r of GSM Carrier s
Numbe r of UMTS Carrier s
Output Power per GSM Carrier (W)
Output Sharing Power per GSM Carrier (W)
Output Power per UMTS Carrier (W)
1
0
40
40
0
2
0
40
40
0
3
0
20
20
0
4
0
20
20
0
5
0
13
15
0
6
0
13
15
0
7
0
10
13
0
8
0
10
13
0
1
1
40
40
40
2
1
20
20
40
3
1
13
15
40
4
1
10
13
40
Power specifications of various RF modules are different. For power specifications of a specific RF module, check the RF module's specifications.
To check specifications of an RF module, download the document by clicking http://3ms.huawei.com/mm/docMaintain/mmMaintain.do? method=showMMDetail&f_id=GSM201201310032.
4 Parameter Configuration Parameters for UMTS900 and UMTS2100 cells should be configured consistently except for interoperation-related and UMTS inter-carrier-mobility-related parameters.
3 Network Implementation 1 Policy for Deploying the UMTS900 The preceding analysis shows that the inter-system interference is the minimum when GSM900 BTSs and UMTS900 BTSs are deployed in 1:1 mode. In addition, the more sites sharing the antenna, the less impact on the performance. Therefore, it is recommended that you guide customers to deploy GSM900 BTSs and UMTS900 BTSs in 1:1 mode. You can guide customers in the following aspects. Although the voice services served by the UMTS900 network are better than those served by the GSM900 network, the same number of GSM900 BTSs are required to ensure the data services at an appropriate rate. A single module of Huawei SRAN BTS can provide both the GSM900 and UMTS900 networks. In addition, the GSM900 and UMTS900 networks can share the antenna system, reducing the site deployment cost. In the segmental networking scenario where GSM900 sites and UMTS900 sites are not deployed in 1:1 mode, the GSM900 and UMTS900 networks cannot share the antenna system if the UMTS900 network requires continuous coverage. In this case, two modules are required, doubling the site deployment cost.
Huawei SRAN3.0 consists of mRRU and mRFU. mRFU provides a higher maximum transmit power through only one RF channel. If the GSM900 and UMTS900 networks use one module for networking and share the antenna, the GSM900 and UMTS900 TRXs share the same PA, causing legal risks. mRRU provides a maximum transmit power lower than that provided by mRFU through two RF channels. If the GSM900 and UMTS900 networks use one module for networking and share the antenna, GSM900 TRXs and UMTS900 TRXs use two different PAs respectively, avoiding legal risks. In summary, mRFU and mRRU have their own advantages and disadvantages. Therefore, you should choose the appropriate module with the local rules and strategies of operators taken into account in the application of Refarming solutions.
2 UMTS900 Hardware Installation Before activating the UMTS900, you need to connect the physical cables of the network properly and check whether the ports on WBBPs are sufficient. For details about the tools used for connecting cables, visit http://3ms.huawei.com/mm/docMaintain/mmMaintain.do? method=showMMDetail&f_id=GSM201103210059. Some operators want to visit the site just once for hardware installation and cell commissioning to reduce costs, such as the Australia OPTUS project. Since the GSM900 has not released its frequencies, activating the UMST900 will cause a frequency conflict. As a result, an alarm is reported on the base station. If operators want to activate the UMTS900 for an intermodulation test, they can use the frequency of other operators' for the test. They need to deactivate the UMTS900 immediately after the test and then change the UMTS frequencies to activate the UMTS900 cells after the GSM900 frequency release.
3 Activating the UMTS900 1
Set up UMTS900 cells and set the correct pilot and maximum transmit power based on the UMTS900 power planning.
2
Set the parameters related to camping, cell reselection, inter-frequency and inter-system handovers, and load control for the UMTS900 based on the traffic bearer scheme.
3
On the NodeB LMT, run the SET FREQBWH command to set the minimum effective bandwidth for the UMTS900.
4
Set UMTS900, UMTS2100, and GSM900 cells as neighboring cells for one another.
5
Activate UMTS900 cells.
4 Setting the UMTS Filter Currently, the CME has not achieved in implementing frequency-based adjustment of the UMTS filter settings. The default bandwidth of the UMTS filter is 5 MHz. When the UMTS900 site is initiated, the settings of the UMTS filter should be optimized according to the frequency configuration of the GSM900; otherwise, carrier alarms are generated or network performance is degraded. UMTS filter parameters are cell level ones. You can set these parameters by running the SET FREQBWH command on the NodeB LMT. If the parameters are not set, the default UMTS 5.0 MHz filter is used. After setting the parameters, you can query the current UMTS filter setting by running the LST FREQBWH command. 1 describes the UMTS filter settings for different bandwidths. 1
Non-standard UMTS filter settings Scenario
Principle for Setting UMTS Filters
UMTS networking using 4.6 MHz
The minimum central frequency point separation between UMTS and GSM is 2.4 MHz.
All UMTS filters are set to 4.4 MHz.
UMTS networking using 4.2 MHz
The minimum central frequency point separation between UMTS and GSM is 2.2 MHz.
All UMTS filters are set to 4.2 MHz.
UMTS networking using 3.8 MHz
The minimum central frequency point separation between UMTS and GSM is 2.0 MHz.
All UMTS filters are set to 3.8 MHz.
4 Network Optimization and Acceptance 1 UMTS Network Optimization RTWP Optimization According to project experience, the major performance problem after the UMTS900 activation lies in the RTWP. Therefore, the RTWP of each UMTS900 cell must be monitored. If the RTWP is greater than -104 dBm, measures must be taken to handle the problem. For details about the handling operations, see reference [13]. A high RTWP may be caused by any of the following:
Physical cable connections
If the problem is caused by hardware connections, engineers must check the physical cable connections onsite.
Antenna intermodulation If the problem is caused by the antenna intermodulation, an intermodulation interference test must be conducted during off-peak hours. First start TRX idle timeslot test on GSM to observe the RTWP of the UMTS900, and then start the test on UMTS900 to observe the RTWP of the UMTS900. In indoor distribution scenarios, if antennas are co-sited with GSM micro base stations, you can initiate services to several users, and raise the download transmit power to observe whether the RTWP of UMTS900 cells is increasing. If the RTWP increase is noticeable during the TRX idle timeslot tests on GSM and UMTS900, for example, 3 dB, there is intermodulation interference, and engineering personnel are required to handle the problem.
Improper antenna tilt If the GU common antenna is used, after the UMTS900 is activated, the UMTS network uses the antenna tilt used by the GSM network. In the UTMS900, if the KPIs are poor or the RTWP is high, you need to conduct a drive test, check for the cross-cell coverage, and optimize the antenna tilt.
External signal interference If the problem seems to be caused by external signal interference, identify the source of the external interference onsite.
Improper bufferzone planning Check the bufferzone based on the planning to determine whether the bufferzone is too small and consequently affecting the UMTS900 KPIs.
Interoperation Parameter Optimization Check whether ping-pong handovers occur between GSM and UMTS networks by checking whether the following condition is met: Qqualmin + SsearchRat < FDDQMIN If the penetration rate of UMTS900 terminals is high, the UMTS900 network absorbs large traffic, causing heavy load. You need to change inter-frequency handover parameters between the UMTS900 and UMTS2100 to balance the load between UMTS carriers.
Other UMTS KPI Optimization Check other UMTS KPIs by following the UMTS KPI optimization action or using the NPMaster. For details, visit http://support.huawei.com/support/pages/editionctrl/catalog/ShowVersionDetail.do? actionFlag=clickNode&p_line=&node=000001410349&colID=ROOTENWEB| CO0000000174&
2 UMTS Network Acceptance After the UMTS900 is activated, it is recommended that you accept the UMTS900 by comparing the UMTS900 KPIs withUMTS900+UMTS2100 KPIs after the Refarming, not the KPIs of the UMTS900+UMTS2100(before the Refarming).
3
Refarming Scenarios
The GU900 Refarming has been implemented at many sites. 1 lists the cases of Refarming on live networks. 1
Cases of Refarming scenarios
No.
Telecom Operato r
Scenari o
UMTS Bandwidt h
Traffic Migration Direction
GSM Frequency Reuse After the Refarming
New Feature
1
France SFR
Suburban areas
4.2 MHz
GSM1800/UM TS
Baseband frequency hopping
2
Hungary Vodafone
Suburban areas
4.2 MHz
Baseband frequency hopping
3
Thailand AIS
Entire network
5 MHz
Baseband frequency hopping
UMTS evolving from one carrier to two carriers
4
Egypt Vodafone
Urban areas
4.2 MHz
GSM900 tight frequency reuse
1x3 RF hopping
UISS+IBCA+VAM OS
5
Hongkong Hutchison
Urban areas
4.6 MHz
GSM1800/UM TS2100
Baseband frequency hopping
6
China Unicom in Guangzhou
Subways
3.8 MHz
Baseband frequency hopping
7
Poland P4
Urban areas
3.8 MHz
RFU multi-site cell networking
RFU multi-site cell
Reference Documents [1] CommunicaAsia 2009 Summit: Spectrum for Mobile Broadband –Low Frequency Options, GSA. [2] HSDPA capacity gain in the 900 MHz band, Nadia Khaji, Salah Eddine Elayoubi and Frédéric Marache, Orange Labs. [3] UMTS900_GSM900 Networking Technical Proposal V1.2, an internal Huawei document, Zhou Honggang, 2008.6 [4] Simulation Analysis for India IDEA, an internal Huawei document, Yang Liping, Zheng Xiang, 2009.7 [5] RNPS SRAN3.0 Technical Clarification on Feasibility of Antenna Sharing by GSM and UMTS V1.0, an internal Huawei document, Deng Shoufeng, Ji Yongjun, He Xiaomei, Zhuang Yanli, Huang Shengli, Zheng Xiang, Yang Liping, 2009.09 [6] Co-Antenna Network Solution for GSM and UMTS Systems, an internal Huawei document, Ji Yongjun, 2009.11 [7] 3GPP TS 25.816 V7.0.0, UMTS 900 MHz Work Item Technical Report [8] 3GPP TS 45.005 V8.5.0 (2009-05) Radio transmission and reception (Release 8) [9] 3GPP TS 25.104 V9.0.0 (2009-05) Base Station (BS) radio transmission and reception (FDD) (Release 9) [10] GU frequency Separation Analysis V1.8, an internal Huawei document, Lu Peng, Yang Liping, Xiong Bin, 2009.4 [11] Analysis on GU Central Frequency Separation, an internal Huawei document, Yang Liping, Xiong Bin, 2009.07 [12] "Impact on system performance from IM relaxation for MCPA application", GP-080231, TSG GERAN #37, Erission. [13] SRAN3.0 Impact of GU Coexistence on Performance, an internal Huawei document, Yang Liping, 2009.10 [14] Impact of UMTS Flexible Bandwidth on Performance, an internal Huawei document [15] Performance Improvement Plan and Solution for Refarming V1.0, an internal Huawei document, Xiong Bin, 2009.08 [16] Analysis on Isolation Distance between UMTS and Co-Band Heterosystem V1.1, an internal Huawei document, Guo Kuanxin, 2009.08 [17] GSM Frequency Planning Solution for Refarming V0.5, an internal Huawei document, Li Guowei, 2009.07
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[18] SRAN Refarming GSM-UMTS Buffer Zone Solution, an internal Huawei document, Deng Shoufeng, 2010.4 [19] Risk Analysis in France SFR, an internal Huawei document, Xiong Bin, 2009.12 [20] GTS NTS Dept.Joint Sta.No. [2010] 011-Specifications of KPI Commitment in GSM Refarming Service
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