Radio Frequency Engineering

GSM Base Station Subsystem (BSS) KPI analysis

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GSM BSS KPI analysis
KPI means for key performance indicator, which is measure from all the related aspect of network such as call setup success rate (CSSR), Handover success rate (HOSR), Paging, network access, congestion etc. From KPI report Radio Network Optimizer’'s took decision or provide prescription for the network. For KPI analysis usually data is collected from drive test of Radio Access Network (RAN), error log of network equipment and Base Station Controller (BSC) data. After combining data we can draw symmetric graph using GSM KPI tools.
Short lists of GSM KPI tools:
  • Mapinfo.
  • TEMS Investigatation.
  • TEMS Route Analyzer.
  • Genex Probe.
  • Genex Assistant.
  • NEMO.
  • ACTRIX Analyzer.
  • Microsoft Excel and Microsoft Access
There are numerous KPI and optimization tools for GSM network, but above tools are widely used. From BSC we collect traffic data and system performance data, this data represent salient status of the network, resource utilization, Hardware load etc. After analyzing this data we can make decision on network planning, network monitoring and network performance.
BSS KPI Issue:
  • Paging success rate
  • Standalone dedicated control Channel (SDCCH) availability rate.
  • Standalone dedicated control Channel (SDCCH) congestion rate.
  • Immediate assignment success rate.
  • Standalone dedicated control Channel (SDCCH) call drop rate.
  • Traffic channel (TCH) call drop rate.
  • Traffic channel (TCH) congestion rate.
  • Traffic channel (TCH) assignment success rate.
  • Handover Success rate (HOSR)
  • Call setup success rate (CSSR)
  • Call complete success rate (CCSR)
     Above thirteen issues are important for network performance and this issues are directly impacts on the user experience about the network. On the other hand every single issue is depending on the multiple variables and as well as each other. Like low success rate of Handover (HOSR) decreases Call complete success rate (CCSR) and increases dropped call rate (CDR). Lower value of KPI depends on flowing:
  • Geo and Meta data issues.
  • Network Planning and implementation error (Such as cell mismatch, mismatch on RF parameter and antenna orientation, High VSWR and DTF etc ).
  • Hardware failure (BTS/RBS down time or off air time) or Hardware Capacity issues (limited capacity of hardware responsible for network congestion, it's also decreases network access rate).
  • Resource constraint (Frequency Band and Absolute radio frequency channel number - ARFCN, low height for serving antenna, low transmission capacity).
A GSM KPI’s widely depends on the network parameter; such as azimuth, mechanical tilting, electrical tilting, feeder length, feeder type and antenna height etc. Mismatch on network parameter decreases the KPI value. KPI is also depends on the core and transmission network parameter.
Note: GSM network may classified into three parts, these are
Ideal value of KPI is 100, expressed in percentage. In practical it’s not possible to achieve 100. But you should try to increase KPI values as much as possible. A good example of high KPI is Airtel network in Bangladesh. It’s about 94% in R2 region; R2 region is eastern belt of country, from Sylhet to Cox’s Bazaar including Comilla and Chittagong.