GSM 09.02 - Version 5.3.0 - Digital cellular telecommunications - ETSI

Page 432
GSM 09.02 Version 5.3.0: August 1996
Call Released by Calling Subscriber
This may occur at any stage during the call set up procedure. Call release is indicated to the MSC by a
Release Message (I_REL). The MSC will then terminate the procedure towards the VLR using the
MAP_U_ABORT service. The User Reason will indicate Application Procedure Cancellation and the
Diagnostic Information will indicate Call Release. If at the time the procedure is terminated the call has
already been confirmed by the MS, i.e. the MS has responded to the set up message (A_SETUP) by
returning a call confirmed message (A_CALL_CONF), then the resources associated with the mobile
terminating side of the call should also be released (i.e. mobile station and base station resources). The
procedure in the MSC is then terminated.
No Paging or Search Response
If the timer for paging expires, paging may be repeated n times. The number of successive paging
attempts and the time intervals are a network dependent choice. If the paging fails the MSC informs the
VLR in the MAP service response (either MAP_PAGE or MAP_SEARCH_FOR_MS) with the user error
set to "Absent Subscriber". If the Call Forwarding on MS Not Reachable service is not active, the VLR will
terminate the procedure by returning a MAP_SEND_INFO_FOR_INCOMING_CALL service confirm with
the user error set to "Impossible Call Completion". The MSC will then send a Release message (I_REL) to
the Gateway MSC to release the call.
If Call Forwarding on MS Not Reachable is active, then the call will be forwarded as described below in the
Call Forwarding subclause.
Called Subscriber Not Reachable
In response to the MAP_SEND_INFO_FOR_INCOMING_CALL service request the VLR may inform the
MSC that the subscriber cannot be reached. If Call Forwarding on MS Not Reachable service is not active,
this notification is contained in a MAP_SEND_INFO_FOR_INCOMING_CALL service confirm with the user
error set to "Absent Subscriber". To terminate the procedure, the MSC will send a Release message
(I_REL) to the Gateway MSC to release the call.
If Call Forwarding on MS Not Reachable service is active, then the call will be forwarded as described
below in the Call Forwarding subclause.
Access to Called Subscriber Not Possible
The VLR, in response to the request from the MSC to provide information for the called subscriber
(MAP_SEND_INFO_FOR_INCOMING_CALL service request) may detect an error condition. This is
reported in the MAP_SEND_INFO_FOR_INCOMING_CALL service confirm with the user error indicating
one of the following:
Unallocated Roaming Number;
Unknown Subscriber;
Unexpected Data Value;
Data Missing;
System Failure.
To terminate the procedure for this call the MSC will send a Release Message (I_REL) to the Gateway
MSC to release the call.