GSM 09.02 - Version 5.3.0 - Digital cellular telecommunications - ETSI

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GSM 09.02 Version 5.3.0: August 1996
Error handling
In case some error is detected during handling the access request, a respective error has been set.
Before returning this error cause to the MSC in a MAP_PROCESS_ACCESS_REQUEST response, it
need to be checked whether this access is for emergency call set-up, as this will require extra treatment.
If the CM Service type given in the MAP_PROCESS_ACCESS_REQUEST indication is emergency call
set-up, it is checked whether EC set-up in the particular error situation is permitted (operator option). If so,
it is checked whether the IMEI is required, and if so the IMEI is requested from the MS (macro
Obtain_IMEI_VLR, see subclause 21.6).
The macro will terminate immediately with unsuccessful outcome if the MSC transaction has been
aborted during the IMEI retrieval.
In case of an error reported back from IMEI retrieval, MAP_PROCESS_ACCESS_REQUEST
response containing the error cause set previously is returned to the MSC, the dialogue is closed
(MAP_CLOSE request indicating normal release) and the macro terminates with unsuccessful
outcome.
When a subscriber identity required by the operator (IMSI or IMEI) is available, the user error set
previously is deleted, the respective identity is returned in the MAP_PROCESS_ACCESS_REQUEST
response to indicate acceptance of emergency call, and the macro terminates with successful outcome.
In all other cases, the MAP_PROCESS_ACCESS_REQUEST response containing the error cause set
previously is returned to the MSC, the dialogue is closed (MAP_CLOSE request indicating normal release)
and the macro terminates with unsuccessful outcome.
21.4.3 Macro Identification Procedure
This macro is invoked by the macro Process_Access_Request_VLR in case the subscribers identity is not
known in the VLR.
If the identity received from the MS is an IMSI, the error Unidentified Subscriber will be set and reported
back to the calling macro (to be sent in the MAP_PROCESS_ACCESS_REQUEST response). The same
error is used in case a TMSI was received from the MS, but the operator does not allow open
identification of the MS.
If open identification of the MS is allowed, the macro Obtain_IMSI_VLR is invoked, requesting the
subscribers IMSI from the MS (see subclause 21.8), with outcome
OK, in which case it is checked whether for the IMSI received there exists a subscriber record in the
VLR. If so, the macro terminates successfully, else the error Unidentified Subscriber will be set and
reported back to the calling macro.
Error, in which case the error System Failure will be set and reported back to the calling macro.
Aborted, i.e. the MSC transaction is released, in which the macro terminates accordingly.