Radio Frequency Engineering

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




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

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