GSM Radio Optimization Guide

8/13/2019 GSM Radio Optimization Guide

http://slidepdf.com/reader/full/gsm-radio-optimization-guide 1/64

GSM Radio Network Optimization(How To Optimization Network )



Wireless Network Optimization

Common procedure of networkoptimizationData collectionEvaluation of networkNetwork optimizationIntroduce of network optimizationtools

Let’s Begin!



Common Procedure of GSM Network Optimization

Data collection before optimizationNetwork evaluation before optimizationOptimization schemeThe design of optimizationimplementation schemeNetwork evaluation after optimizationLight adjustment solutionEvaluation before completion

Experience communion



Data Collection

• Data collection of current network• Performance data and traffic fromOMC-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



Data Collection Of Current Network-1

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

• Parameters of BTS equipment and Antenna_feedere.g. BTS Max power output, Max Site type Loss ofcomponents of antenna and feeder etc.

• Special function of equipment e.g. Distinctivehandover arithmetic.

• Wireless propagation Environment Clutter Dense cityCommon city Sparse city Suburb Village Landform

platform hill Land and Waters etc. Electronic mapis necessary sometimes



Data Collection Of Current Network-2

• Engineering Data Longitude,latitude of sites AltitudeSite type Capacity Configuration Antenna heightParameters Gain Front_back ratio Horizontal 3dbBeam width Vertical 3db Beam width Electrical downtilt Azimuth of Antenna Length of feeder; TMA,Booster, Repeater used etc.

• Wireless Resource Parameters MCC+MNC+LAC+CIBTS Output power Frequency Hopping BSIC cellselection parameters cell reselection parametershandover parameters BA neighbor cell list SDCCHConfiguration LAC and PCH Location Update etc.



OMC-R Performance Data and Traffic Statistical Data

Statistical data on busy timeData kinds

SDCCH Assign Allocate seizure Success Rate and number of successTCH Assign Allocate seizure Success Rate and number of success

TCH Handover Success Numbers and Success RateTCH Handover Success Numbers and Success Rate Between Dual-band;TCH Call Drop numbers and Drop rateTCH call drop reason (LAPD ,Radio Link etc.)SDCCH Congestion and traffic per subscriberTCH Congestion and traffic per subscriberUsable rate of TRX



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



Test data_ main content

Mode of mobile No Service Idle Dedicated

The co-ordinate of site longitude and latitudeRxLev C1 C2 ; RxQual FER BER ,TA ( Only in Dedicatedmode etc.

Decoding information and other information of neighbor cell

L3 Layer3 information From the layer 3 information ,thewhole communication procedure can be traced

The reselection information



CQT Test

• The special place• Indoor test



Feedback from the subscribers

The time

The place

The problem description

The solution

The contact information of thesubscriber



A_Interface Data

The handover data of each cellThe information of location update

The information of call drop

The traffic



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 distributinginformation of RXLEV quality and number of measurereport TA distributing information the informationof balance between uplink and downlink

All of the signal information between BTS and BSC



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 theinformation shows the network quality as a whole

• Drive test the information shows the network quality as awhole and the quality of particular place,but the result is

random.• Test in special place to find the special problem and test inhot spot

• Feedback from the subscribers complementary informationand the final information

• Collection data from signal analysis equipment you can getthe information of the whole network and detail informationbut lack of the information of downlink um interface and thelocation information

l f k



Evaluation of Network

• Evaluation of the wholenetwork

• Finding reason of theparticular problem



Evaluation of the whole network-1The coverage rate of the whole networkThe quality rate of the whole networkThe handover success rate of the whole networkSDCCH Assign Allocate seizure Success Rateand number of successTCH Assign Allocate seizure Success Rateand number of successTCH Handover Success Number and Success RateTCH Handover Success Number and Success RateBetween Dual-bandTCH Call Drop number and Drop rateTCH call drop reason (LAPD ,Radio Link etc.)SDCCH Congestion and traffic per subscriberTCH Congestion and traffic per subscriberUseable rate of TRX



Evaluation of the whole network-2

• Difference indicators partitionTCH 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 badcell.

Special problem



Special problem

Blind coverage area

The area with bad qualityThe area which call drops oftenThe reason of dropThe cell handover success rate

The TA DistributingThe congestion of the cell

Network optimization



Network optimization

Rudder of network optimization

Common procedure of optimization

Wireless parameter optimization

Wireless resource parameteroptimization



Network Optimization —Rudder 1

One must analyses problem systematically in network

optimization Network is a system Any partialadjustment must be thought in a whole network, negativeeffect must be thought over Specially for theFrequency ,antenna(Wireless parameters)

Try your best to reduce the risk of Optimization1. Avoid adjusting the network frequency continuously.2. Using the software and equipment to simulate the result

of network optimization3. Test in partial area4. 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.



First the global problem ,next the particular problemThe global Problems must be thought about first forexample the congestion of the whole network.Next theproblems 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



Common Procedure

Checking network engineering parametersAntenna and feeder the mistake connection of feeder.The antenna typeThe Engineering parameters of antenna the Height/Azimuth/down tilt of antenna.

The exact and detailed data is the base of networkoptimization

Checking Wireless resource parametersCGI = MCC + MNC + LAI + CIBSIC AND Frequency resource

Common Procedure2



Common Procedure2

Confirming the probable range of the main problemaccording to the network evaluation report.Finding the probable problemsAnalyze the main problemsGive the solution and implementation

Wireless parameters



Wireless parameters

Types of wireless parameters mainly RF Parametersincluding the Parameters of antenna height of antennaazimuth Down tilt output power of BTS FrequencyOthers the propagation Environments

The method of adjustment Using the drive test softwareand network plan software can increase the accuracy ofadjustment.

The main problems The Coverage problems :The weaksignal , the overshoot ,the overlay ; The interference: co-

channel and adjacent channel interference ; The balance oftraffic

Coverage



•BTS output power

•The loss of feeder System

•The antenna type

•The engineering parameters Azimuth Down tilt

•Path Loss

Coverage

• Factors of coverage:



Coverage-Path Loss 1

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

2. Clutter The building is more ,the path loss is more3. The landform plain,hill4. Forest influence About 10 db loss if the microwavepropagates the forest in 20meters

Factors of Path

h



5. Water surface effect: The signal loss near water is very small and isclose to the loss in free space the loss on water surface becomes

larger farther away from the shore, for the phase difference betweenthe direct wave and the wave reflected by the water surface is 180degree, while the intensities are almost the same, hence the receivedsignal is very weak.

6. Obstacle Diffraction loss is caused by obstacles like hills andbuildings. 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-pathpropagation effect.7. Loss through buildings It varies significantly with buildings of

different cities, structures and materials. Usually, for 900MHz theloss is 12~17dB (15dB is usually used) for 1800MHz the loss is18~20dB. The loss also varies with different floors of a building:Usually, the loss reduces about 2dB every floor up. In cold areas, thewalls of builds are usually rather thick, and the loss for 900MHz isabout 18~20dB.

8. Propagation distance Within 1~20km the propagation loss is40dB/dec longer than 20km, the loss is about 50~60dB/dec.

Coverage-Path Loss 2

C A



Coverage-Antenna type

1. Gain2. Polarized Vertical Polarized Dual_ Polarized

3. Vertical and horizontal 3db Beam width4. Front_Back Ratio5. Electrical Down tilt

The important Technology Parameters

60

(eg)Peak

Peak - 3dB

Peak - 3dB

3dB Beamwidth

The Reason of weak signal



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 Horizontal3dB 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

The common method to increase the signal strength



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;

indoor Coverage



indoor Coverage

• Macro cell

• Micro cell indoor• Distributed system indoor

• Repeater and leaking line

Coverage indoor



LocalUnit

Remote Unit

BTS

Splitter

Cable

Fiber

Cable

Antenna

Coverage indoor

Lonely Island



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 islandarea often have interferences

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

CELL A

ISLAND

Lonely Island

Coverage Overlap



1. Some area covered by two or more cells is needed betweentwo cell The area can provide coverage area continuously

and handover well2. The Overlap Area is Suitable for 20%~30% to the wholecoverage area. If the overlap coverage area is big, theerror handovers and call drops appear possibly.

3. SolutionAdjust the wireless parameters plan coverage area for

each cell carefully .Just like adjust the down tilt ofantenna and output power of BTS

g p

The interference problems



The interference problems

1. Noise2. Call Drop3. Low Handover Success Rate4. Can’t Page information increase

The Problems brought by the interference

Reduce the interference



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 cell6. Adjust the height of antenna

Reduce the interference

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

Antenna Down tilt



1. Think about the vertical beam widthof antenna.

2. Calculate method d h/tg(a-t/2)d: radius of cell covering h theeffective height of antenna a thedown tilt degree t : the verticalbeam width of antenna

3. The above formula need

Calculate the down tilt degree of antenna

Height ofantenna

Comparative height

Down tilt Distanceto site

Cell No. Remark

37 57 10 1088 Wuzhi_A The geographic situation is uneven.

Down tilt



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 ifthe down tilt is too much.

Down tilt too much electro- down tilt No down tilt

Frequency Planning



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

Wireless Resource Parameters Optimization



p

1. The content of wireless resource parameters Set atOMC_R ,About the parameters how to use wirelessresource e.g. CGI CCCH combine method PCH blocksSDCCH cell select parameters cell reselect parameterscell handover parameters power control parameters etc..

2. How to adjust the wireless resource parameters Analysisthe performance data ,drive test data to get a resolvedmethod.

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

TCH Congestion



1. MORE TRX Calculate by Erl_B

2. Reduce the coverage Area

3. Adjust the Selection Parameters forexample :RAM

4. Adjust the reselection Parameters forexample: CRO

5. Adjust the Handover Parameters for example:UPLEV

6. Directional Retry

SDCCH Congestion



1. Location update frequently2. 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

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

Adjacent cell



Adjacent cell

1. At MOST :322. Enough is OK ,At first,you can define many ,and reduce some3. If some adjacent cell is left, maybe cause the handover success

rate is low,and if the adjacent cell is important, call dropincrease

The neighbor relation

1. The map2. Drive test

Define the neighbor relation

Dual_Band Network



900 micro 1800 micro

GSM900 macro

GSM1800 macro

P-cell P-cell

_

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

Tool Introduction



• Planning soft planmaster tm2.0

• Drive test tools TEMS SAFCO ANTPILOT

• Signal analysis equipment ocean

GPS

PlanMaster TM2.0



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

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

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

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

Function

PlanMaster TM2.0



Overshooting coverage

BS8107A

PlanMaster TM2.0



Overlap coverage

BS8101A servicearea including

BS8105BS8102 BS8108

etc.

PlanMaster TM2.0



InterferenceInterference analysis

PlanMaster TM2.0



Drive test analysis

Drive testanalysis

PlanMaster TM2.0



Drive test analysis

Ant



Received signal level

Ant



Rxqual

Ant



Handover

Ant



Data replay

OCEAN



Data statistics at A interface-Failure rate of TCHchannel

The statistics shows the rateof abnormally released TCHafter the TCH assignmentcommand is given, including

reasons like TCH assignmentfailure and TCH call drop. TheTCH failure rate showed inthe figure is 2.7%.

OCEAN



Data statistics at A interface-Failure rate of TCH connection

The statistics shows the rateof abnormally released TCHafter the TCH connection isestablished, including reasons

like TCH call drop. The TCHconnection failure rate showedin the figure is 0.6%.

OCEAN



Data statistics at A port –Handover success rate

For most cells, thehandover success rate is

above 95%. This functionreflects the handoversuccess rate between anytwo cells

OCEAN



A-bis interface-Coverage across cells

For the Mechanical FactoryDistrict 3, there are somecalls for TA 20 while there isno call from TA 10 to TA 20,

which is definitely an islandphenomenon.

OCEAN



A-bis interface-Interference

Sometimes there is fairlystrong interference for sometime slots in the District 3 ofthe Police Hospital. It isbecause the remote areas likeDistrict 3 of the PoliceHospital are covered by co-channel cells, or adjacent-channel cells of strongintensity, and when thehandset uses channels of co-

channel or adjacent-channelcells, it is inevitable for thehandset signal to interferesome time slots of the cell.

OCEAN



A-bis interface-Interference

For the District 3 of the PoliceHospital, RQ is larger than 2when the received level is still85dBm which shows thatthere is significantinterference in the cell.

OCEAN



Measure report analysis:

1. Fault phenomenon: the signal coverage of the BS in Qidu ofChizhou Unicom, Anhui, is comparatively weak, but there isno alarm.

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

rvDownrvUpmsoutAnt P P P P

Take the average from many measure reports to determinewhether the output power at the transmitting end of the

antenna is normal3. Result of data analysis: the output power is comparativelysmall.

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

GSM Radio Optimization Guide

Documents

Transcript of GSM Radio Optimization Guide