dcr optimization after swap.doc

7/27/2019 DCR optimization after swap.doc

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How to Improve Call drop rate

Background:in swap project,after swap there were some cells with

worse dcr,in order to improve this kpi,We summarized these aspects and gave

some suggestions:

1 Hardware problem

1.1check the alarm and history alarm,normally it can lead to call drops

due to Equipment Failure.

1.2 reset the site,If there are some call drops due to Equipment Failure

without alarm,maybe there are something wrong with our BTS software.reset

the site with level 4 during night.if also not ok,get the help from BSC guy.

1.3 check the WSWR of the site through MML,if the value of VSWR is

bigger than 1.5,maybe there are something wrong with feeder,TMA,or

antenna and so on.let site enginner go to this site with site master for testing

the VSWR.

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2 DRFU (PBT) Single Feeder(1TX+2RX)

2.3 Neighbors Relationship,we can use Nastar to check the

neighbors,especially missing neighbors.

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2.4 Frequency HSN MAIO and so on.

3 DATA CONFIGURATION

3.1 Coverage Parameters

About this kind problem,firstly we can collect the Measurement from M2000:

Number of MRs based on TA per TRX

Radio Link Failure Measurement per TRX

Radio Link Failure Measurement based on TA per TRX

Receive Quality Measurement per TRX

TCHF Receive Level Measurement per TRX

TCHH Receive Level Measurement per TRX

Uplink-and-Downlink Balance Measurement per TRX

After we anlyzed the report,we can know about the Receive Quality,Level,TA

and so on.if the TA is big for coverage plan,we should control the

coverage.parameters we can adjust as below:

a. RACH Min.Access Level(dbm),default value is -115,recommended value

-109.

b. Random Access Error Threshold, default value is 180, recommendedvalue 220

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c. RXLEV_ACCESS_MIN, default value is 8, recommended value 10.

d. otherwise,we can adjust downtilt and power to control the coverage.

3.2 Interference Parameters

About this kind of problem,we can collect the Measurement from M2000:

Radio Link Failure Measurement per TRX

Receive Quality Measurement per TRX

TCHF Receive Level Measurement per TRX

TCHH Receive Level Measurement per TRX

GSM Cell to GSM Cell Outgoing Handover Measurement

Interference Band Measurement per TRX

After anlysis,if there are high receive level with bad quality,a lot of quality

handovers and interference band are bigger than 3,there maybe

interference,we can adjusted the parameters as below:

a. Radio Link Timeout(SACCH period (480ms)) this parameter is about

downlink, default value is 16, recommended value 52

b. SACCH Multi-Frames(SACCH period (480ms)) this parameter is about

uplink, default value is 18, recommended value 36.

c. T200 FACCH/F(5ms) default value is 50,recommended value 80.

d. T200 FACCH/H(5ms) default value is 50,recommended value 80.e. N200 of FACCH/Half rate, default value is 29,recommended value 50.

f. N200 of FACCH/Full rate, default value is 34,recommended value 50.

g. if there is strong interference through monitoring channel interference

band,we need eliminate it.

3.3 Handover Parameters

About this kind of problem,we can collect the Measurement from M2000:

Incoming Internal Inter-Cell Handover Measurement per Cell

Outgoing Internal Inter-Cell Handover Measurement per Cell

Incoming External Inter-Cell Handover Measurement per Cell

Outgoing External Inter-Cell Handover Measurement per Cell

GSM Cell to GSM Cell Outgoing Handover Measurement

After anlysis,if there is bad hsr between 2 neighbors,and also Cell Outgoing

Handover Fail Reconn Fail happens,we need adjust some handover

parameters as below:

a. Edge HO UL RX_LEV Threshold,default value is 10,recommended value

15.

b. Edge HO DL RX_LEV Threshold,default value is 19,recommended value

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25.

c. Min DL Power on HO Candidate Cell,default value is 10,recommended

value 0.

d. Min UP Power on HO Candidate Cell,default value is 10,recommendedvalue 0.

e. Min Interval for Consecutive HOs,default value is 4,recommended value

2.

f. Min Interval for Emerg.HOs,default value is 4,recommended value 2.

g. Filter Length for TCH Level,default value is 6,recommended value 3.

h. Filter Length for TCH Qual,default value is 6,recommended value 3.

i. DL Qual. Threshold,default value is 55,recommended value 40.

j. UL Qual. Threshold,default value is 55,recommended value 40.

k. MR.Preprocessing, default value is YES,recommended value NO.

About the values of parameters,just recommended,you can decide to choose

according to actual situation, detailed meaning of these parameters,you can

get it from LMT help document,thanks,

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dcr optimization after swap.doc

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