Hi Alonewolves,
you mean t3101 trigger only for ghost rach? I dont think so
it should be pegged for all abis related problem and so timer expiry, not only for ghost rach i guess..
About formula, we use same formula and agai ghost rach not discarded here. I pasted some info from google, check it out, its quite clear ha
Short info for t3101:
T3101 (Default 3s)
When: immediate assignment process
Timer T3101 is used to set the interval between the start time when an IMM ASS message is sent by BSC and the stop time when an EST IND message is reported to BSC. BSC releases the seized SDCCH if no EST IND message is received within the time specified by timer T3101.
Normal flow
MS → RACH → BSC
MS ← IMM ASS ← BSC (start counting the timer)
MS → EST IND → BSC (stop the timer)
Abnormal flow
1). MS → RACH → BSC
MS X IMM ASS ← BSC (start counting the timer)
In this case IMM ASS message is not received by the MS. Then BSC will release the seized SDCCH after waiting the time specified by timer T3101.
2). MS → RACH → BSC
MS ← IMM ASS ← BSC (start counting the timer)
MS X EST IND X BSC
In this case, ESTIND message is not sent by the MS after receiving IMM ASS message. The BSC will release seized SDCCH channel as above case.
3). MS → RACH → BSC
MS ← IMM ASS ← BSC (start counting the timer)
MS → EST IND X BSC
In this case ESTIND message is sent by MS. But BSC does not receive ESTIND message. The seized SDCCH channel will release as above cases.