2023年4月17日 1

GSM Radio Network Optimization(How To Optimization Network)

2023年4月17日 2

Wireless Network Optimization

Common procedure of network

optimization

Data collection

Evaluation of network

Network optimization

Introduce of network optimization tools

Let’s Begin!

2023年4月17日 3

Common Procedure of GSM Network Optimization

Data collection before optimization Network evaluation before

optimization Optimization scheme The design of optimization

implementation scheme Network evaluation after

optimization Light adjustment solution Evaluation before completion Experience communion

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Data Collection

• Data collection of current network； • Performance data and traffic from OMC-R

；

• Driving test data； • Test data in special place； • Feedback from the subscribers ； • A interface and a-bis interface trace

data by signal analysis equipment ；• Usage of all kinds of data

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Data Collection Of Current Network-1

• Parameters of BSC ： e.g. Max Capacity 、 Phase2+ support ?etc.

• Parameters of BTS equipment and

Antenna_feeder ： e.g. BTS Max power output, Max Site type 、 Loss of components of antenna and feeder etc.

• Special function of equipment ： e.g. Distinctive

handover arithmetic.

• Wireless propagation Environment ：Clutter （ Dense city 、 Common city 、 Sparse city 、 Suburb 、 Village ）；Landform （ platform 、 hill 、 Land and Waters etc. ）。Electronic map is necessary sometimes ；

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Data Collection Of Current Network-2

• Engineering Data ： Longitude,latitude of sites 、 Altitude 、 Site type （ Capacity Configuration ）、Antenna height 、 Parameters （ Gain 、、 Front_back ratio 、 Horizontal 3db Beam width 、 Vertical 3db Beam width 、 Electrical down tilt ）、 Azimuth of Antenna 、 Length of feeder; TMA, Booster, Repeater used etc. ；

• Wireless Resource Parameters ：（ MCC+MNC+LAC+CI ）、 BTS Output power 、 Frequency Hopping 、 BSIC 、 cell selection parameters 、 cell reselection parameters 、 handover parameters 、 BA 、 neighbor cell list 、 SDCCH Configuration 、 LAC and PCH 、 Location Update etc. ；

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OMC-R Performance Data and Traffic Statistical

Data

Statistical data on busy time

Data kinds ： SDCCH Assign 、 Allocate 、 seizure Success Rate and number of

success  TCH Assign 、 Allocate 、 seizure Success Rate and number of

success  TCH Handover Success Numbers and Success Rate ； TCH Handover Success Numbers and Success Rate Between

Dual-band;  TCH Call Drop numbers and Drop rate  TCH call drop reason (LAPD ,Radio Link etc.)  SDCCH Congestion and traffic per subscriber  TCH Congestion and traffic per subscriber   Usable rate of TRX

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Test_Object And Classification

• DT test: the quality evaluation of the whole network;• Frequency scanning test: checking internal or

external interference ;• CW test: propagation model correction test;• Cell reselection border test;• Cell handover border test;• Interference cause confirmation;

MacrocellMacrocell

MicrocellMicrocell

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Test data_main content

Mode of mobile （ No Service ， Idle ， Dedicated ）；

The co-ordinate of site （ longitude and latitude ）；

RxLev ， C1 、 C2 ; RxQual 、 FER 、 BER ,TA ( Only in Dedicated mode ） etc. ；

Decoding information and other information of neighbor cell ；

L3 （ Layer3 ） information ； From the layer 3 information ,the whole communication procedure can be traced ；

The reselection information

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CQT Test

• The special place• Indoor test

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Feedback from the subscribers

      The time ；

The place ；

The problem description ；

The solution ；

The contact information of the subscriber ；

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A_Interface Data

The handover data of each cell ；

The information of location update ；

The information of call drop ；

The traffic ；

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A-bis data

The main information you can get ：

The whole signal procedure ；

The uplink signal between MS and Network ；

From the analysis of measure report ： the distributing information of RXLEV 、 quality and number of measure report ； TA distributing information ； the information of balance between uplink and downlink ；

All of the signal information between BTS and BSC

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The usage of all kinds of data

• Data collection of current network ： the basic of network optimization;

• OMC-R performance data and traffic statistical data ： the information shows the network quality as a whole ；

• Drive test ： the information shows the network quality as a whole and the quality of particular place,but the result is random.

• Test in special place ： to find the special problem and test in hot spot ；

• Feedback from the subscribers ： complementary information and the final information ；

• Collection data from signal analysis equipment ： you can get the information of the whole network and detail information ， but lack of the information of downlink um interface and the location information ；

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Evaluation of Network

• Evaluation of the whole network

• Finding reason of the particular problem

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Evaluation of the whole network-1

The coverage rate of the whole network ；

The quality rate of the whole network ； The handover success rate of the whole

network SDCCH Assign 、 Allocate 、 seizure Success

Rate and number of success ； TCH 、 Assign 、 Allocate 、 seizure Success

Rate and number of success ； TCH Handover Success Number and Success

Rate ； TCH Handover Success Number and Success

Rate Between Dual-band TCH Call Drop number and Drop rate ； TCH call drop reason (LAPD ,Radio Link

etc.) ； SDCCH Congestion and traffic per

subscriber ； TCH Congestion and traffic per subscriber ； Useable rate of TRX ；

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Evaluation of the whole network-2

• Difference indicators partition  TCH Congestion ： 0%~2% ， 2%~5% ， 5%~10% ， 10%~20% ， >20% ；

         TCH Handover Success Rate ：<60% ， 60%~80% ， 80%~90% ， 90%~95% ， >95% ；

         TCH Drop Rate ： <1% ， 1%~2% ， 2%~5% ， 5%~10% ， >10% ；

        Traffic Per Channel ： <0.2 ， 0.2~0.3 ， 0.3~0.4 ， 0.4~0.5 ， 0.5~0.6 ， >0.6 ；

Through the statistical Method ,we can find the bad cell.

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Special problem

Blind coverage area ； The area with bad quality ； The area which call drops often ； The reason of drop ； The cell handover success rate ； The TA Distributing ； The congestion of the cell ；

2023年4月17日 19

Network optimization

Rudder of network optimization

Common procedure of optimization

Wireless parameter optimization

Wireless resource parameter

optimization

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Network Optimization—Rudder 1

One must analyses problem systematically in network optimization ： Network is a system ， Any partial adjustment must be thought in a whole network, negative effect must be thought over 。 Specially for the Frequency ,antenna(Wireless parameters) ；

Try your best to reduce the risk of Optimization ：1. Avoid adjusting the network frequency continuously. 2. Using the software and equipment to simulate the

result of network optimization 3. Test in partial area 4. The good implementation procedure is

needed,Especially when the adjustment job lasts long time , the adjustment must be executed step by step.

5. Backup of the current network data6. Adjust in the lowest traffic time7. Explain to the Subscribers if necessary.

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First the global problem ,next the particular problem ：

The global Problems must be thought about first for example the congestion of the whole network.Next the problems in special place be thought about.

First the Wireless parameters （ Engineering Parameters,Next the wireless resource Parameters.

From the hot areas to others ： The main problems to minor problems 。

Network Optimization—Common Rule 2

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Common Procedure

Checking network engineering parameters ： Antenna and feeder ： the mistake connection of

feeder. The antenna type ： The Engineering parameters of antenna ： the

Height /Azimuth/down tilt of antenna.

The exact and detailed data is the base of network optimization 。

Checking Wireless resource parameters ：CGI = MCC + MNC + LAI + CI 。BSIC AND Frequency resource 。

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Common Procedure2

Confirming the probable range of the main problem according to the network evaluation report.

Finding the probable problems Analyze the main problems Give the solution and implementation

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Wireless parameters

Types of wireless parameters ： mainly （ RF ） Parameters ， including the Parameters of antenna 、 height of antenna 、 azimuth 、 Down tilt 、 output power of BTS 、 Frequency 。 Others ， the propagation Environments 。

The method of adjustment ： Using the drive test software and network plan software can increase the accuracy of adjustment.

The main problems ： The Coverage problems :The weak signal , the overshoot ,the overlay ; The interference: co-channel and adjacent channel interference ; The balance of traffic 。

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•BTS output power

•The loss of feeder System

•The antenna type

•The engineering parameters ： Azimuth 、 Down tilt

•Path Loss

Coverage

• Factors of coverage:

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Coverage-Path Loss1

1. Height of antenna ： according to 20lg(h /30) ,the higher antenna the less path loss 。

2. Clutter ： The building is more ,the path loss is more 。3. The landform ： plain,hill 。 4. Forest influence ： About 10 db loss if the microwave propa

gates the forest in 20meters 。

Factors of Path

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5. Water surface effect: The signal loss near water is very small and is close to the loss in free space ； the loss on water surface becomes larger farther away from the shore, for the phase difference between the direct wave and the wave reflected by the water surface is 180 degree, while the intensities are almost the same, hence the received signal is very weak.

6. Obstacle ： Diffraction loss is caused by obstacles like hills and buildings. The diffraction loss can be calculated by principle of Huygens. Buildings near to the BS will cause larger shadows, while shadows caused by buildings far away are smaller because of the multi-path propagation effect.

7. Loss through buildings ： It varies significantly with buildings of different cities, structures and materials. Usually, for 900MHz ， the loss is 12~17dB (15dB is usually used) ； for 1800MHz ， the loss is 18~20dB. The loss also varies with different floors of a building: Usually, the loss reduces about 2dB every floor up. In cold areas, the walls of builds are usually rather thick, and the loss for 900MHz is about 18~20dB.

8. Propagation distance ： Within 1~20km ， the propagation loss is 40dB/dec ； longer than 20km, the loss is about 50~60dB/dec.

Coverage-Path Loss2

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Coverage-Antenna type

1. Gain2. Polarized ： Vertical Polarized 、 Dual_

Polarized 。 3. Vertical and horizontal 3db Beam width 。 4. Front_Back Ratio5. Electrical Down tilt 。

The important Technology Parameters

60° (eg) Peak

Peak - 3dB

Peak - 3dB

3dB Beamwidth

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The Reason of weak signal

1. BTS Output Power 。

2. The loss of Feeder_Antenna ， Alarm of VSWR ；

3. Between the Directional antennas （ Outside of Horizontal 3dB Beam width ）

4. The tilt of Omni_Antenna ；

5. The height of antenna ；

6. The antenna type ： For example :the gain is too low ；

7. The Path Loss is big ： Landform or forest ；

8. The wrong type of antenna ；

WHY No signal ？

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The common method to increase the signal strength

1. Increase Output Power 。

2. Reduce the Loss of antenna and feeder ；

3. Use the high gain antenna if possible ；

4. Change the azimuth of the antenna ；

5. Change the down tilt of the antenna.

6. Higher the Height of antenna ；

7. Add new site ；

8. Use Repeater;

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indoor Coverage

• Macro cell

• Micro cell indoor

• Distributed system indoor

• Repeater and leaking line

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Local Unit

Remote Unit

BTS

Splitter

Cable

Fiber

Cable

Antenna

Coverage indoorCoverage indoor

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1. Phenomenon ： The coverage area of one cell is divided into two or more parts.

2. Reason ： The coverage is overshooting.

3. Result ： bring call drops if the some neighbor relations are not defined. frequent handover ； The congestion because of the big coverage ； The island area often have interferences ；

4. Solution ： Reduce the coverage,adjust the down tilt of the cell etc.

CELL A CELL B

ISLAND

Lonely Island

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1. Some area covered by two or more cells is needed between two cell ： The area can provide coverage area continuously and handover well 。

2. The Overlap Area is Suitable for 20%~30% to the whole coverage area. If the overlap coverage area is big, the error handovers and call drops appear possibly.

3. Solution ：Adjust the wireless parameters ， plan coverage area

for each cell carefully .Just like adjust the down tilt of antenna and output power of BTS 。

Coverage Overlap

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The interference problems

1. Noise2. Call Drop3. Low Handover Success Rate 4. Can’t Page information increase

The Problems brought by the interference

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1. Increase the signal of BTS2. Reduce the coverage area of the main cell3. Good frequency Plan.4. Select the suitable antenna5. Adjust Down tilt of the interference cell 6. Adjust the height of antenna

Reduce the interference

Object ： Increase the signal of main service cell ,reduce the signal strength of interference

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Antenna Down tilt

1. Think about the vertical beam width of antenna.

2. Calculate method ： dh/tg(a-t/2) ，d: radius of cell covering ， h the effective height of antenna ， a the down tilt degree ， t : the vertical beam width of antenna 。

3. The above formula ， need 。

Calculate the down tilt degree of antenna

Height of antenna

Comparative height

Down tilt Distance to site

Cell No. Remark

37 57 10 1088 Wuzhi_A The geographic situation is uneven.

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Down tilt

Unsuitable big direct down tilt can bring big problems through the alternant coverage.

We suggest that we use direct and electro-down tilt together if the down tilt is too much.

Down tilt too muchelectro- down tiltNo down tilt

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Frequency Planning

1. Solve the co-channel problem2. Solve the adjacent channel problem

The problems solved by Frequency optimization

1. The regular BCCH Reuse :at least 4*3 ， better 5*3.2. BCCH use the continuous frequency used by BCCH

only.3. BCCH not frequency hopping.

Main point of frequency optimization

2023年4月17日 40

Wireless Resource Parameters Optimization

1. The content of wireless resource parameters ：， Set at OMC_R ,About the parameters how to use wireless resource ， e.g. CGI 、 CCCH combine method 、 PCH blocks 、 SDCCH 、 cell select parameters 、 cell reselect parameters 、 cell handover parameters 、 power control parameters etc..

2. How to adjust the wireless resource parameters ：Analysis the performance data ,drive test data to get a resolved method.

3. the problems can be dealt with ： capacity /call drop / others 。

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TCH Congestion

1. MORE TRX ， Calculate by Erl_B 。

2. Reduce the coverage Area ；

3. Adjust the Selection Parameters for example :RAM 。

4. Adjust the reselection Parameters for example: CRO 。

5. Adjust the Handover Parameters for example: UPLEV 。

6. Directional Retry ；

2023年4月17日 42

SDCCH Congestion

1. Location update frequently 。 2. High traffic

The Reason of SDCCH Congestion

1. At the border of location2. Alone cell3. High traffic 。

SDCCH Congestion Cell Features

1. SDCCH/42. SDCCH/8

SDCCH Channel Method

Increase the SDCCH channel number

The solution to solve SDCCH congestion

LAC

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Power control

Control TRX Max output power

Static power control

1. Reduce the noise of whole cell2. Reduce the power of MS

Dynamic Power Control

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Adjacent cell

1. At MOST :32 ；2. Enough is OK ,At first,you can define many ,and reduce

some ；3. If some adjacent cell is left, maybe cause the handover

success rate is low,and if the adjacent cell is important, call drop increase 。

The neighbor relation

1. The map ；2. Drive test

Define the neighbor relation

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900 micro 1800 micro

GSM900 macro

GSM1800 macro

P-cell P-cell

Dual_Band Network

1. Provide a method for big capacity2. Use the same site location of GSM 900M , Cost is low ；

Strongpoint

1. Handover parameters 。2. Reselect parameters for traffic ；

Method of optimization

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Tool Introduction

• Planning soft ： planmastertm2.0 ；

• Drive test tools ： TEMS ， SAFCO ， ANTPILOT ；

• Signal analysis equipment ： ocean ；

GPS

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PlanMasterTM2.0

1. Evaluate the radio environment by coverage analysis, co-channel interference analysis, and adjacent channel interference analysis. Simulate and analyze the adjustment effect of radio parameters for optimization.

2. Adopt e-map to make the most of the distribution information of landforms, natural features and buildings to determine the antenna down tilt more reliably.

3. Provide the set of adjacent cells of each cell after the radio parameters are adjusted.

4. Discover radio problems by analyzing the Drive test data.

Function

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PlanMasterTM2.0

Overshooting coverage

BS8107A

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PlanMasterTM2.0

Overlap coverage

BS8101A service area including

BS8105 、BS8102 、 BS810

8 etc.

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PlanMasterTM2.0

Interference Interference analysis

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PlanMasterTM2.0

Drive test analysis

Drive test analysis

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PlanMasterTM2.0Drive test analysis

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Ant

Received signal level

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AntRxqual

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Ant

Handover

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Ant

Data replay

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OCEAN

Data statistics at A interface-Failure rate of TCH channel

The statistics shows the rate of abnormally released TCH after the TCH assignment command is given, including reasons like TCH assignment failure and TCH call drop. The TCH failure rate showed in the figure is ： 2.7%.

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OCEAN

Data statistics at A interface-Failure rate of TCH connection

The statistics shows the rate of abnormally released TCH after the TCH connection is established, including reasons like TCH call drop. The TCH connection failure rate showed in the figure is ：0.6%.

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OCEAN

Data statistics at A port –Handover success rate

For most cells, the handover success rate is above 95%. This function reflects the handover success rate between any two cells

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OCEAN

A-bis interface-Coverage across cells

For the Mechanical Factory District 3, there are some calls for TA 20 ， while there is no call from TA 10 to TA 20, which is definitely an island phenomenon.

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OCEAN

A-bis interface-Interference

Sometimes there is fairly strong interference for some time slots in the District 3 of the Police Hospital. It is because the remote areas like District 3 of the Police Hospital are covered by co-channel cells, or adjacent-channel cells of strong intensity, and when the handset uses channels of co-channel or adjacent-channel cells, it is inevitable for the handset signal to interfere some time slots of the cell.

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OCEAN

A-bis interface-Interference

For the District 3 of the Police Hospital, RQ is larger than 2 when the received level is still 85dBm ， which shows that there is significant interference in the cell.

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OCEAN

Measure report analysis:

1. Fault phenomenon: the signal coverage of the BS in Qidu of Chizhou Unicom, Anhui, is comparatively weak, but there is no alarm.

2. Problem location: shut down the power control of uplinks and downlinks of this BS ， and trace the measure reports of some call processes at the A-bis interface of the BS with the signaling analyzer. According to the principle of equal loss for uplinks and downlinks, use the following formula:

rvDownrvUpmsoutAnt PPPP Take the average from many measure reports to

determine whether the output power at the transmitting end of the antenna is normal

3. Result of data analysis: the output power is comparatively small.

4. Solution: Replace the power amplifier, and it can be settled.

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