Hello Ayat,
You’re asking the same question in three threads, but i’ll just answer here :
you can divide the call phase in four sub-phases :
1- sdcch assignment (MS asks the BTS to get a SDCCH, thanks to BCCH channel)
2- sdcch phase (exchange of info between MS and NSS on the dedicated SDCCH)
3- tch assignment (BTS requires a TCH and allocate it to the MS)
4- tch phase (exchange of speech frames on the dedicated TCH)
as far as i can see, you have 3 TCH counters :
TCH allocated
TCH assigned
TCH seizure
You must know that a counter is incremented in the BSC as soon as the BSC sends (or receives) a ABIS message. Check the description of those counters, and find the message to which they’re associated.
Finally, get the 3GPP doc about the message flows for call setup (sorry don'(t have the ref…)