GSM Multi-sector Solution Guide(GSM BSS Draft a)

GSM BSS

GSM Multi-sector Solution Guide Issue

Draft A

Date

2015-05-15

HUAWEI TECHNOLOGIES CO., LTD.

Copyright © Huawei Technologies Co., Ltd. 2015. All rights reserved. No part of this document may be reproduced or transmitted in any form or by any means without prior written consent of Huawei Technologies Co., Ltd.

Trademarks and Permissions and other Huawei trademarks are trademarks of Huawei Technologies Co., Ltd. All other trademarks and trade names mentioned mentioned in this document are the property of of their respective respective holders. holders.

Notice The purchased products, services and features are stipulated by the contract made between Huawei and the customer. All or part of the products, services and features described in this document document may not be within the purchase scope or the usage scope. Unless otherwise specified in the contract, all statements, information, information, and recommendations in this document are provided "AS IS" without warranties, guarantees or representations of any kind, either express or implied. The information in this document is subject to change without notice. Every effort has been made in the preparation of this document to ensure accuracy of the contents, but all statements, information, and recommendations recommendations in this document do not constitute a warranty of any kind, express or implied.

Huawei Technologies Co., Ltd. Address:

Huawei Industrial Industrial Base Bantian, Longgang Shenzhen 518129 People's Republic of China

Website:

http://www.huawei.com

Email:

[email protected]

Issue Draft A (2015-05-15)

Huawei Proprietary and Confidential Copyright © Huawei Technologies Co., Ltd.

i

GSM BSS GSM Multi-sector Solution Guide

Contents

Contents 1 About This Document..................................................................................................................1 1.1 Scope..............................................................................................................................................................................1 1.2 Intended Audience..........................................................................................................................................................1 1.3 Change History...............................................................................................................................................................1

2 Overview.........................................................................................................................................2 2.1 Background.....................................................................................................................................................................2 2.2 Overall Scheme...............................................................................................................................................................2 2.2.1 Dual-beam Antennas/Narrow-beam Antennas............................................................................................................3 2.2.2 Frequency Planning.....................................................................................................................................................4 2.3 Application Scenario......................................................................................................................................................4

3 Hardware Selection.......................................................................................................................7 3.1 Antenna Selection...........................................................................................................................................................7 3.2 RF Module Selection......................................................................................................................................................8 3.3 Connection Mode...........................................................................................................................................................9

4 Delivery Process...........................................................................................................................12 4.1 Scenario Identification..................................................................................................................................................13 4.2 Network Planning.........................................................................................................................................................13 4.2.1 Frequency Planning...................................................................................................................................................13 4.2.1.1 ARFC N Planning....................................................................................................................................................13 4.2.1.2 BSIC Planning........................................................................................................................................................14 4.2.1.3 HSN and MAIO Planning.......................................................................................................................................14 4.2.2 RF Planning...............................................................................................................................................................15 4.2.3 Neighboring Cell Planning........................................................................................................................................15 4.3 Network Optimization..................................................................................................................................................15 4.3.1 RF Optimization........................................................................................................................................................15 4.3.2 Frequency Optimization............................................................................................................................................16 4.3.3 Neighboring Cell Optimization.................................................................................................................................16 4.3.4 General Optimization................................................................................................................................................16

5 Acronyms and Abbreviations...................................................................................................17 6 Reference Documents.................................................................................................................18 Issue Draft A (2015-05-15)


ii


1 About This Document

1

About This Document

1.1 Scope This document describes the multi-sector solution which increases network capacity without adding spectrums or sites. Using the spatial multiplexing technique, Huawei dual-beam antennas, and network optimization, this solution helps operators meet challenges in network capacity.

1.2 Intended Audience This document is intended for personnel who: l l

Need to understand the solution described herein Work with Huawei products

1.3 Change History This section provides information about the changes in different document versions.

Draft A (2015-05-15) This is the first commercial release.



1


2 Overview

2

Overview

2.1 Background GSM spectrum resources are becoming less with the fast refarming development. However, subscribers on the GSM network will not migrate to other networks in the near future, and the demand on GSM network capacity remains great in a short term. To help operators meet the challenge in network capacity, the multi-sector solution is introduced. Using the spatial multiplexing technique, Huawei dual-beam antennas, and network optimization, this solution increases network capacity without adding spectrums or sites.

2.2 Overall Scheme The multi-sector solution uses dual-beam antennas or narrow-beam antennas to achieve small sector coverage area. Together with proper frequency planning and increased frequency reuse rate, this solution increases system capacity by 30% to 70%. Figure 2-1 shows the implementation of the GSM multi-sector solution.



2


2 Overview

Figure 2-1 GSM multi-sector implementation

This solution uses dual-beam antennas or narrow-beam antennas and involves frequency planning and GSM multi-sector related techniques.

2.2.1 Dual-beam Antennas/Narrow-beam Antennas The GSM multi-sector solution uses the following antennas: l

Narrow-beam antenna: Its beam half-power angle is 33 degrees, which is half of that of a three-sector antenna. Two narrow-beam antennas provide the same coverage as a common antenna and therefore can be used for sector splitting.

l

Dual-beam antenna: It splits a beam of a common antenna into two well-isolated beams and therefore can be used for sector splitting.

Figure 2-2 Narrow-beam antenna and dual-beam antenna



3


2 Overview

2.2.2 Frequency Planning Frequency planning for the multi-sector solution is as follows: l

l

Back-to-back intra-frequency planning: Front-to-rear power of the antenna directivity diagram is high. Based on this, have the two cells in back-to-back mode use the same frequency and remain the original three-sector frequency planning unchanged. Non-back-to-back intra-frequency planning: The included angle of the main lobe is small, making it easy to avoid overlapping areas covered by main lobes of neighboring sites. Based on this, traverse frequencies for planning using the U-Net and obtain the optimal frequency planning which has minimum intra-network co- and adjacent-channel interference.

2.3 Application Scenario The GSM multi-sector solution helps increase network capacity by increasing the TRX reuse times per area and improve uplink and downlink coverage using dual-beam antennas. Dual-beam antennas bring 1 to 3 dB gains compared with traditional 65-degree antennas. This solution is used in the following scenarios: 1.

2.

Capacity-required scenarios where the following conditions are met: l

The proportion of cell-level half rate traffic volume for voice services during peak hours is greater than 80%, or the traffic channel (TCH) congestion rate is greater than 2%.

l

Site acquisition is difficult, and sites cannot be added.

Weak coverage scenarios where the weak coverage and bad quality ratio is greater than or equal to 4% l

The weak coverage and bad quality ratio is the percentage when the receive quality level ranges from 4 to 7, the uplink level is less than –95 dBm, and the downlink level is less than –90 dB.

3.

Refarming scenarios where frequency bands are saved for UMTS/LTE (UL) networks

4.

GUL co-site scenarios where UMTS or LTE sectors have been split and GSM sectors are to be split to save space

Restrictions of this solution are as follows: l

When co-BCCH or enhanced dual-band network is enabled, the multi-sector reconstruction must be performed on both frequency bands.

l

IBCA is mutually exclusive with this solution.

l

When traffic is severely unbalanced among sectors, for example, traffic concentrates in some sectors and cannot be distributed to other sectors by sector splitting, the multi-sector solution is not recommended.

l

When strip-shaped areas are in the same direction of sector coverage, especially in highspeed mobility scenarios, the multi-sector solution is not recommended.

l

If antennas are not selected based on the GSM multi-sector antenna selection plan, the expected system capacity cannot be achieved.

l

When the included angle between azimuths is less than 100°, sector splitti ng is not recommended.



4

GSM BSS GSM Multi-sector Solution Guide l

2 Overview

Traffic migration occurs after sector splitting. Therefore, verify the solution gain by checking cluster-level counters.

Continuous-area Reconstruction In this scenario, sites in a continuous area are reconstructed to multi-sectors. Because narrow beam antennas are used in the reconstruction area and unified frequency planning is performed, intra-network interference is easy to control, bringing a significant capacity gain. The following table provides capacity gains for different bandwidths at the 1800 MHz frequency band when Huawei split antenna AMB4520R0 is used for continuous-area reconstruction. For a satisfactory capacity gain, it i s recommended that the reconstruction cover more than 20 sites.

Frequency Bandwidth

Capacity Gain

3.0 MHz to 3.8 MHz

10% to 30%

3.8 MHz to 6.2 MHz

30% to 45%

6.2 MHz to 10 MHz

45% to 55%

> 10 MHz

55% to 70%

The following table provides capacity gains for different bandwidths at the 900 MHz frequency band in the continuous-area reconstruction.

Frequency Bandwidth

Capacity Gain

3.0 MHz to 3.8 MHz

8% to 25%

3.8 MHz to 6.2 MHz

25% to 35%

6.2 MHz to 10 MHz

35% to 45%

> 10 MHz

45% to 56%

Mixed Networking Reconstruction On the live network, mixed networking reconstruction is performed when some sites in a continuous area require capacity expansion. In the reconstruction, frequencies are re-planned for all cells in the continuous area to ensure that intra-network interference is controllable. The proportion of sites for mixed networking reconstruction varies with the frequency reuse rate. If the proportion is excessively low, the advantage of narrow-beam antennas to control interference in the three- and multi-sector hybrid network is compromised. In this case, co- and adjacent-channel interference cannot be eliminated, and the network quality deteriorate.



5


2 Overview

Table 2-1 GSM multi-sector reconstruction

BCCH Frequency Reuse Pattern

TCH Frequency Reuse Pattern

Reconstructio n Scale (Site Quantity)

Recommende d Site Reconstructio n Quantity

Minimum Interference Protection Area

BCCH 3x3

/

20 sites

20 sites

Neighboring cells of two layers

BCCH 4x3

TCH 1x3

20 sites

Neighboring cells of two layers

TCH 2x3

10 sites

Neighboring cells of one layer

TCH 3x3

7 sites

None

TCH 4x3

5 sites

None

The mixed networking reconstruction is performed on a certain proportion of sites. Therefore, its gain is about 80% of the gain brought by the continuous-area reconstruction when the preceding conditions are met.

Weak Coverage Dual-beam antennas or narrow-beam antennas provide greater coverage gain than traditional three-sector antennas and therefore are used in networks with high requirements on coverage. The quantitative coverage gain is determined by the gain difference between the dual-beam antenna/narrow-beam antenna and the three-sector antenna on the live network, which is about 2 dB.



6


3 Hardware Selection

3

Hardware Selection

3.1 Antenna Selection Table 3-1 Antenna selection

Model

Manuf Band acturer Class

Gain

Horizo Electri ntal c Tilt Beam Width (°)

Specif Weigh ication t (Unit: s kg)

21

33

0

2577 x 591 x 182

21.3

Narrow -beam antenna

824-89 0

17.9

39

0-10

32.5

890-96 0

18.2

36

2090 x 504 x 118

Dual beam antenna

1710-1 990

19.2

34

0-10

18.3

1920-2 200

19.7

31

1468 x 349 x 166

Dual beam antenna

2200-2 490

20

29

2490-2 690

20.2

27

(dBi)

(MHz)

LBX-3 319DST0M

Andre w

2CPX2 08RV1

Argus

AMB4 520R0

Huawei


806-89 6 870-96 0


Anten na Type

(H x W x D) (mm)

7


Model


Manuf Band acturer Class

Gain (dBi)

(MHz)

Horizo Electri ntal c Tilt Beam Width (°)

Specif Weigh ication t (Unit: s kg)

Anten na Type

(H x W x D) (mm)

DX-69 0-960-3 3-20.5i -M-R

Huawei

690-96 0

20.5

33

0-10

2580 x 590 x 169

400

Narrow -beam antenna

HBXX3817T BVTM

Andre w

1710-1 880

19.2

38

0-10

15

1850-1 990

19.6

38

1390 x 301 x 181

Dual beam antenna

1920-2 180

19.8

35

For the 1800 MHz frequency band, Huawei antenna AMB4520R0 is recommended. For the 900 MHz frequency band, Huawei antenna DX-690-960-33-20.5i-M-R is recommended.

3.2 RF Module Selection In principle, types of radio frequency (RF) modules for multi-sector capacity expansion are the same for the six sectors. Specifically, you are advised to use R F modules of the same type as that configured on the original three sectors or having replacement relationships with the original RF modules unless RF modules of the original three sectors are to be changed. For example, macro base stations use radio frequency units (RFUs), and distributed base stations use remote radio units (RRUs). In special scenarios, to facilitate multi-sector capacity expansion, RRUs can be added to macro base stations to serve newly added sectors. RF modules in 1T2R and 2T2R modes are independently configured on each sector. The number of RF modules configured on each sector varies depending on the TRX number, bandwidth, power, and frequency band. In 2015, Huawei introduces a 2T4R RRU (RRU3953) for distributed base stations. The 2T4R RRU can be shared by two sectors, thereby saving RRU installation clearance. Table 3-2 RF module selection Module

RRU393 6

RRU393 9

RRU365 9

RRU395 3

MRFUv 2

MRFUd

MRFUe

Frequen cy Band

900/180 0 MHz

1800 MHz

900 MHz

1800 MHz

900 MHz

900/180 0 MHz

1800 MHz



8



Support ed RAT

G/U/L

G/U/L

G/U/L

G/U/L

G/U/L

G/U/L

G/U/L

Channel

1T2R

2T2R

2T2R

2T4R

1T2R

2T2R

1T2R

Output Power

1 x 80 W

2 x 60 W

2 x 60 W

2 x 80 W

1 x 80 W

2 x 80 W

1 x 125 W

Maximu m Number of Cascadi ng Levels

6

6

6

6

2

2

2

Require d Quantit y

6

6

6

3

6

6

6

GSM: 2 x 60 W

NOTE

The RF modules are software-defined radio (SDR) modules and support evolution to the UMTS or LTE sites. They can be used when the multi-sector solution is used in multiple radio access technologies (RATs). The RF modules can be cascaded to save the number of required common public radio interface (CPRI) ports on the BBU.

3.3 Connection Mode The connection mode varies with the antenna and RF modules types.



9



Figure 3-1 Connection between 1T2R/2T2R RF modules and narrow-beam antennas (dual receiving)

Figure 3-2 Connection between 1T2R/2T2R RF modules and dual-beam antennas (dual receiving)



10



Figure 3-3 Connection between 2T4R RF modules and dual-beam antennas (dual receiving)

Figure 3-4 Connection between 2T4R RF modules and narrow-beam antennas (dual receiving)



11


4 Delivery Process

4

Delivery Process

Figure 4-1 Delivery process



12


4 Delivery Process

4.1 Scenario Identification The multi-sector solution is used in capacity-required scenarios where the following conditions are met: l

The proportion of cell-level half rate traffic volume for voice services during peak hours is greater than 80%, or the TCH congestion rate is greater than 2%.

l

Site acquisition is difficult, and sites cannot be added.

The accurate site planning (ASP) tool can be used to filter target scenarios and antenna initial parameters. NOTE

The ASP of the current version supports scenario identification and of the version released in May of 2015 supports multi-sector antenna initial parameter planning. Before that time, manually set antenna initial parameters.

4.2 Network Planning 4.2.1 Frequency Planning Frequency planning of the multi-sector reconstruction is performed using the U-Net. Figure 4-2 shows the frequency planning process. Figure 4-2 Frequency planning process

4.2.1.1 ARFCN Planning The multi-sector absolute radio frequency channel number (ARFCN) planning falls into the following types: Issue Draft A (2015-05-15)


13

GSM BSS GSM Multi-sector Solution Guide l

4 Delivery Process

Back-to-back intra-frequency planning: Front-to-rear power of the antenna directivity diagram is high. Based on this, have the two cells in back-to-back mode use the same frequency and remain the original three-sector frequency planning unchanged. This planning method is recommended when sectors are split to five or six sectors and is not recommended in 1x3 or 2x3 scenarios and single-site reconstruction scenarios. Working principles of this method are as follows:

– In the interference matrix, interference matrices of the two back-to-back cells are combined.

– Frequencies are planned based on the combined interference matrix, and available frequencies are obtained. Figure 4-3 Back-to-back intra-frequency planning

l

Non-back-to-back intra-frequency planning: The included angle of the main lobe is small, making it easy to avoid overlapping areas covered by main lobes of neighboring sites. Based on this, traverse ARFCNs using the U-Net and use the optimal frequency plan which has minimum intra-network co- and adjacent-channel interference.

4.2.1.2 BSIC Planning The base transceiver station identity code (BSIC) planning for the multi-sector solution is the same as that for the common three-sector solution. During the planning, obey the following principles: l

A serving cell and its neighboring cells cannot be configured with the same BCCH and same BSIC.

l

Neighboring cells of a serving cell cannot be configured with the same BCCH and same BSIC.

l

The BCCH and BSIC reuse distance must be as long as possible for cells with the same BCCH and same BSIC.

For details on planning BSICs based on the topology relationship using the U-Net, see GSM Frequency Planning Technical Guide.

4.2.1.3 HSN and MAIO Planning The hopping sequence number (HSN) and mobile allocation index offset (MAIO) planning for the multi-sector solution is similar to that for the three-sector solution. HSN planning principle: Cells using the same MA cannot use the same HSN. If HSN resources are insufficient, ensure that the HSN reuse distance is as long as possible. In the three-sector Issue Draft A (2015-05-15)


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4 Delivery Process

solution, HSNs of cells under the same site are the same. However, in the multi-sector solution, if the back-to-back intra-frequency planning is used, HSNs for back-to-back cells must be different to avoid intra-frequency interference. MAIO planning principles: Each TRX involved in the frequency hopping (FH) is assigned with an MAIO. The MAIO value, indicated by L, ranges from 0 to l, which is obtained by subtracting 1 from the MA length.

For details on planning HSNs and MAIOs based on the topology relationship using the U-Net, see GSM Frequency Planning Technical Guide .

4.2.2 RF Planning Perform RF planning based on the actual situation and comply with the following principles: l

Enable sector antennas to face the overlapping areas of the two sectors under two neighboring base stations.

l

Prevent the main lobes of sectors under two neighboring base stations from facing each other.

l

Prevent the situation that important areas are covered by overlapping areas. During the RF planning, take traffic balance into consideration.

In actual engineering parameter planning, to avoid back interference caused by signal back spillover in the back-to-back intra-frequency continuous area construction, you are advised to set the mechanical downtilt angle to 0 degrees and adjust the electrical downtilt angle to optimize network coverage.

4.2.3 Neighboring Cell Planning The multi-sector reconstruction increases the number of sectors as well as the number of neighboring cells. When the number of neighboring cells reaches the threshold, which is 64 for a single cell, perform neighboring cell planning based on the topology relationship using the U Net.

4.3 Network Optimization When the multi-sector solution is used in urban areas (especially in densely populated urban areas), due to complicated geographical environment, more sectors, and increased traffic volume, network interference becomes more severe, and the number of neighboring cells increases, leading the network performance to fluctuate. This section describes the solutions to the problem.

4.3.1 RF Optimization RF engineering parameter modification based on actual situations can resolve most problems in signal coverage and interference. Specifically, it can eliminate coverage holes as well as control coverage and interference. Generally, RF optimization involves modifications of antenna downtilt, azimuth, position, and height. The modification principles are the same as that for RF planning. If the U-Net is deployed on the live network, collect measurement reports (MRs) for automatic cell planning (ACP) simulation and RF parameter optimization. If the U-Net is not deployed on Issue Draft A (2015-05-15)


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4 Delivery Process

the live network, modify RF parameters based on the site geographic display, drive test (DT) data, traffic statistics, and actual situations.

4.3.2 Frequency Optimization This section describes how to modify BCCH and TCH frequencies and BSICs t o decrease intranetwork co- and adjacent-channel interface and thereby improve network quality. If the Nastar is deployed on the live network, collect MR data and traffic statistics and perform partial adjustment using the Nastar. For a large-scale adjustment, frequency refarming is recommended. If the Nastar is not deployed on the live network, or few cells are interfered, manually modify BCCH frequencies and BSICs for top cells. Enable the BCCH and BSIC reuse distance to be as long as possible, preventing co- and adjacent-channel interference and cells with the same BCCH and BSIC.

4.3.3 Neighboring Cell Optimization Neighboring cell optimization includes adding missing neighboring cells and deleting redundant neighboring cells. If the Nastar/SONMaster or U-Net is deployed on the live network, detect missing and redundant cells based on MRs using the Nastar/SONMaster ANR function. Alternatively, detect missing neighboring cells based on the topology relationship and coverage prediction using the U-Net. If the Nastar/SON Master or U-Net is not deployed on the live network, detect missing neighboring cells and redundant cells based on the site geographic display, DT data, and traffic statistics.

4.3.4 General Optimization After RF optimization, frequency optimization, and neighboring cell optimization, check and optimize common performance problems, for example, check RF channels and parameters and analyze traffic statistics. For details, see the GSM troubleshooting guide.



16


5 Acronyms and Abbreviations

5

Acronyms and Abbreviations

Acronym or Abbreviation

Full Name

ACP

automatic cell planning

AFP

automatic frequency planning

ASP

accurate site planning

B2B

back to back

RF

radio frequency

ANR

automatic neighbor relation

IBCA

Interference Based Channel Allocation

SDR

software-defined radio



17


6 Reference Documents

6

Reference Documents

None



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GSM Multi-sector Solution Guide(GSM BSS Draft a)

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