SRAN
GU Refarming Network
Solution
Issue 3.0 Date 2012-09-28 INTERNALCopyright © Huawei Technologies Co., Ltd. 2012. All rights reserved.
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SRAN
GU Refarming Network Solution About This Document
About This Document
Author
Prepared by SRAN Solution Design Department
Date 2012-06-07
Reviewed by Date yyyy-mm-dd
Reviewed by Date yyyy-mm-dd
Granted by Date yyyy-mm-dd
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 About This Document
Date 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.
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
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
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.
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
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.
2.2MHz
4.2MHz steeper filter
2.6MHz
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
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.
2.6MHz 2.6MHz U5.0M 2.4MHz 2.6MHz U4.8M 2.4MHz 2.4MHz U 2.2MHz 2.4MHz U 2.2MHz 2.2MHz U 2.2MHz 2.0MHz U4.0M 2.0MHz 2.0MHz U3.8M
(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.
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
UMTS UE
GSM MS
(1)
(4)
(3)
(2)
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 16QAM-enabled 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 network-level 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 network-level 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.
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 co-located 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).
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.
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 re-selections 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.
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.
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 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 2 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.
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.