TCH Block Rate Optimization Tips in Huawei GSM

TCH Block Rate is familiar KPI in GSM Networks. TCH Block rate indicate percentage of blocking on TCH(Traffic channel) due to lack of traffic channel in a cell. In this note I would like to share how to optimize TCH Bloking rate step by step in order to reduce TCH blocking and configure channel capacity based on traffic needed. Below are steps you need to follow based on my daily optimization activity in my project in Indonesia.

• Check for hardware, make sure no hardware issue.

Hardware checking always the first thing you need to check. You have to make sure no hardware issue before go to next optimization step.Your next action will be useless if the problem of the KPI is hardware issue.If found hardware issue please follow up first to FLM(Field Maintenance) or Project Team to check and troubleshoot. You can check from active alarm and especially from TCH Availability to make sure no TRX module faulty. If found no hardware issue then go to next step.

• Check for Coverage, make sure no Overshooting

Coverage also need to check to make sure no overshooting and cover so far area that will trigger TCH Blocking due to cover unnecessary location and huge traffic.If found overshooting then you need to adjust Antenna tilt.If found no problem with coverage the go to next step.

• Check for Current Channel Configuration, make sure no over dimension of other channel(SDCCH, BCH and PDTCH)

Current channel configuration need to check to make sure no over dimension of other channel(ex:SDCCH,BCH or PDTCH). For SDCCH You can refer to number of TRX, usually the number of SDCCH in a cell same as number of TRX on that cell(ex: number of SDCCH =2 if TRX number =2), except for other case such as high SD traffic cell or covering Event, number of SDCCH may be different. for BCH usually maximum 2 channel in 1 Cell. and for PDTCH usually 1 static PDTCH for 1 TRX(same as SDCCH),except for high PS Traffic cells. After make sure no over dimension channel of other channel(beside TCH), then go to next step

• Calculate TCH needed based on Erlang B Calculation

Now you need to generate measurement related TCH Traffic maximum on the Cell then calculate besed on Erlang B Table. After get TCH Traffic measurement on Busy Hour Cells then you can calculate how many channel needed to accommodate TCH traffic. Click here to calculate channel required for TCH based on Erlang B calculation.

• Change Half Rate Threshold/Re-Dimension Channel/Upgrade TRX

Based on Elang B calculation now you get how many channel TCH needed to accommodate traffic on TCH. Then you can go to Upgrade or Change other Channel into TCH or Change Half Rate setting(TCHBUSYTHRES/AMRTCHPRIORLOAD in Huawei Parameter).You can go to upgrade TRX if Half rate setting already maximum(TCHBUSYTHRESS=0) and additional channel required need add TRX ( 1 TRX = 8 Channel TCHFR) and also no possibility to change other channel into TCH.

Summary to Optimize TCH Block rate:
- Check Hardware problem, make sure no hardware problem occurred.
- Check Coverage, make sure no overshooting to avoid cells cover unnecessary traffic/Covering far area.
- Check Channel Configuration, make sure no over dimension of other channel(SDCCH, BCH and PDCH)
- Calculate TCH Needed based on Erlang B Calculation
- Change Half Rate Setting(TCHBUSYTHRESS and AMRTCHPRIORLOAD)/Channel re-dimension(Change other channel into TCHFR)/Upgrade TRX

You might also Need to know:
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- GPRS Packet Data Access Rate(PDASR) Improvement in Huawei GSM
- Call Drop Rate Improvement by Parameter change in 3G Huawei