The drive test was performed using a 90sec. call, and after that, a redial (almost 100 Call Setups sequences).
This problem was found on 26% of the Call Setups, in different cells, but the same LA.
In that cases, the handshiking was as follows:
UL Channel Request
DL Immediate Assignment
DL Ciphering Mode Command
UL Ciphering Mode Complete
DL Identity Request
UL Identity Response
DL Call Proceeding
DL Assignment Command
UL Assignment Complete
DL Disconnect (20 sec. after Ch. Req.)
UL Release (Call End – NW Initiated Release)
DL Release Complete
DL Channel Release
So, there is an Assignment Complete msg, but there’s no Alerting msg.
We ask MSC administrators in order to ask for a signaling trace.