GSM 09.02 - Version 5.3.0 - Digital cellular telecommunications - ETSI

16.1.1.2 Detailed procedure in the MSC
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GSM 09.02 Version 5.3.0: August 1996
Figure 16.1.1/4 shows the MSC process for location register updating, containing macro calls for:
Receive_Open_Cnf subclause 21.1;
Authenticate_MSC subclause 21.5;
Check_IMEI_MSC subclause 21.6;
Obtain_IMSI_MSC subclause 21.8;
Trace_Subscriber_Activity_MSC subclause 21.9.
For structuring purposes, the second part of the process is placed into the macro Update Location
Completion MSC, which is specific to this process (see figure 16.1.1/5).
When the VLR receives an A_LU_REQUEST (normal location updating, periodic location updating or IMSI
attach) for a subscriber via the radio path, the MSC opens a dialogue to the VLR (MAP_OPEN request
without any user specific parameters) and sends a MAP_UPDATE_LOCATION_AREA request, containing
the parameters provided in the A_LU_REQUEST by the MS or BSS (for the parameter mapping see
TS GSM 09.10).
If the dialogue is rejected or the VLR indicates a fallback to the version 1 procedure (see
Receive_Open_Cnf macro in subclause 21.1), the MSC will send an A_LU_Rej towards the MS and
terminate the procedure.
If the dialogue is accepted, the VLR will process this updating request, invoking optionally the
MAP_PROVIDE_IMSI, MAP_TRACE_SUBSCRIBER_ACTIVITY, MAP_CHECK_IMEI or the
MAP_AUTHENTICATE services first (see subclause 16.1.1.3 for initiation conditions, subclause 21 for
macros defining the handling of services in the MSC). For these macros there are two possible outcomes:
- a positive outcome, in which case the process continues waiting for the
MAP_UPDATE_LOCATION_AREA confirmation; or
- an error is reported, in which case the process terminates (not applicable for
Trace_Subscriber_Activity_MSC, which has only a positive outcome).
After receiving the MAP_UPDATE_LOCATION_AREA indication and handling these optional services, the
VLR will decide whether a new TMSI need to be allocated to the subscriber or not.
Updating without TMSI reallocation
If the VLR does not reallocate the TMSI, the MSC will receive a MAP_UPDATE_LOCATION_AREA
confirmation next (figure 16.1.1/4).
- if there are no parameters with this primitive, updating was successful and a confirmation will be
sent to the MS;
- if there is an error cause contained in the received primitive, this cause will be mapped to the
corresponding cause in the confirmation sent to the MS (see TS GSM 09.10 for the mapping of
messages and causes).