Just have a look at the indicator formula…
CSSR = (1 – TCH ASSIGN UNSUCCESS RATE) * (1 – SDCCH DROP RATE)
CSR = (1 – CALL DROP RATE) * CSSR
For example :
CSSR = 95%
CDR = 10%
Therefore the CSR = 90% * 95% = 85.5%
The CSR is just a mega-KPI, aggregating CSSR and CDR within one indicator. Useless for troubleshooting, but nice for management reporting.