HI MOHIT,
Bro conceptually its very simple..as the name suggests , CSSR , is only about the call setup success…which means if the traffic channel assignment is done ,regardless of whether the call is dropped later on through an abnormal release(none or just one of the two user entities completing the release), it is considered a setup success…the reference here is obviously , total number of calls made by the user…
However , CSR ,tells us the percentage of calls that follow a normal release (both user entities completing the release or other normal causes such as release iniated by IN through the msc , when balance ends…)..the reference here is again the total number of calls made by the user..thats y its always aggregated with the CSSR value…
we always get,CSSR>CSR REALISTICALLY…