In alcatel (WOOOOWWWW YEAH !) there is a TA filter applied on channel resquests.
If TA(chan.req) > RACH TA FILTER, the channel request is not processed
during a call : the TA cannot be used to detect a “call drop”. The only application of TA is to detect a HO. If the TA > U_TIME_ADVANCE, then a neighbour cell is chosen.
If there is no neighbour, the call is kept in the current cell. A high TA is not a reason for a call drop (at least, not in alcatel)
Soft, Hard… Whatever, in Alcatel, it’s just the truth.