WCDMA BSS CS Drive Test (DT) KPI Measurement and Analysis

WCDMA BSS CS KPI: 

WCDMA BSS CS KPI

 

BSS (Base station subsystem) CS (Circuit Switched) KPI (Key performance indicator) means for overall WCDMA (Wide band code division multiple access) voice KPI. To measure WCDMA  BSS CS KPI you need to use flowing software:

• Genex probe or Tems investigation or Nemo Outdoor (Log collection software).

• Genex Assistant or Tems discovery or Actix Analyzer (Log analysis software).

•  Mapinfo professional 11.5 SCP (data presentation software)

• Google Earth (Mapping tool).

The flowing equipment requires to collect WCDMA log files from Um interface:

• Mobile Station (MS) Sony Ericsson W995 for Tems investigation or Huawei U1251 for Genex Probe.
• GPS NMEA (WGS84),  Model No: BU353

•  PC (processing speed minimum core i5).

• Inverter (as a portable power source).

CS KPI includes the flowing parameter measurement and analysis:

• Call setup success rate (CSSR).

• Call completeness success rate (CCSR).

• Average call setup time (CST).

• Average SQI MOS (Speech quality index mean opinion score) value.

• Coverage rate score.

• Handover success rate (HOSR).

• Blocked call rate (BCR).

• Dropped Call rate (DCR). 

Log collection procedure and equipment assembly: 
To measure WCDMA BSS CS KPI you need at least three mobile station (ms) and a GPS. MS1 and MS2 used to collect SQI MOS value and MS3 used to collect rest of the KPI values. MS3 is in short call mode 30 seconds for each call with 10 seconds as a interval. Number of short call is infinite; that is during the entire test period short call will be continued.

KPI Analysis:
After log collection you need to analyze the log to extract desired raw data to calculate KPI. The required analysis tools described in above. For every KPI there is at least a KPI equation. you have to put exact value from raw data for every variables.

Call setup success rate (CSSR):
Call setup success rate is the rate ration of number of call attempt and number of successful setup. Expressed in percentage.

CSSR = (number of successful call setup/number of call attempt)* 100 %

Call completeness success rate (CCSR):
Call completeness success rate is the ration of number of user defined call end and number of call established.

CCSR= (number of user defined call end/number of call established)*100

Average Call Setup Time: 
Call setup time time is the total time required to established a call between to user.
Average call setup time = (total call setup time for "N" number of call/ "N" number of call)*100

Call Setup time

Average SQI MOS value:

Actually SQI MOS (Speech quality index mean opinion score) represents the speech quality of WCDMA CS network. The calculation of SQI MOS, which is defined by the ITU-T PESQ (Perceptual evaluation of Speech Quality) P.862 standard. SQI MOS value ranges from 1 to 5 according to ITU-T PESQ P.862 standard. 

Here, score 1 means worst (Very annoying), score 2 means bad ( Annoying), score 3 means fair ( Slightly annoying), score 4 means good (Perceptible but not annoying), score 5 means best ( Imperceptible).

Geographically distributed SQI MOS Values

Coverage rate score:

There are numerous equation to calculate Coverage rate based on the RSCP (Received Signal Code Power) and EcIo, one of the standard equation based on RSCP is given bellow:

Coverage Rate Score(%) = (A%*10+B%*8+C%*6+D%*1)/10

 Here, A is 0 to -74dbm

B is -74dbm to -82dbm

C is  -82dbm to -98dbm

D is -98dbm to -120dbm

Handover success rate (HOSR): 

Actually, there are two types of Handover in WCDMA one is soft handover another is Hard handover. The equation of handover success rate is given bellow:

HOSR = (Number of successful handover/Number of handover attempt)*100

   Inverse of CSSR (Call setup success rate) is BCR (Blocked call rate),

BCR= (100- CSSR)

Inverse of CCSR (Call completeness success rate) is DCR (Dropped call rate)

DCR = (100-CCSR)

Related Articles:

• How to calculate Call Setup time.
• GSM BSS KPI Analysis
• RF Planning and Optimization Viva question 

GSM Base Station Subsystem (BSS) KPI analysis

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.

• Google Earth 

•  Google Map

• 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) availability.

• 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)

• Call setup delay (Ideal value of call setup time is bellow 3.5 seconds).

     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

• Radio access network (RAN)

• Core network (CN) and

• Transmission network (TN).

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.

Related articles

• How to Calculate Call Setup Time in GSM or WCDMA
• RF Planning and Optimization question (wimaxtec.blogspot.com)
• Implementation Of 4G network in Bangladesh (wimaxtec.blogspot.com)