9 Unsuccessful call setup

03.043GPPSignalling Requirements Relating to Routing of Calls to Mobile SubscribersTS

This clause deals with those cases which are specific to calls to a mobile subscriber. The case where the called subscriber does not subscribe to the service required by the call is the same as for a call to a subscriber on the fixed network.

9.1 Roaming Not Allowed

If the called MS has roamed to a PLMN where it is not allowed service, the HLR has no location information for the called MS. If Call Forwarding on MS Not Reachable is active, the HLR returns the forwarded-to number in response to the interrogation as described in subclause 8.1. If Call Forwarding on MS Not Reachable is not active, the HLR returns an error response to the interrogation.

If the called MS has roamed to a location area where it is not allowed service, the HLR contains the identity of the VLR to which the MS has roamed, but the MS is marked as detached in the VLR. The VLR therefore returns an ‘absent subscriber’ error in response to the request for an MSRN. If Call Forwarding on MS Not Reachable is active, the HLR returns the forwarded-to number in response to the interrogation as described in subclause 8.1. If Call Forwarding on MS Not Reachable is not active, the HLR returns an error response to the interrogation.

9.2 VPLMN Cannot Support The Required Service

If the called MS has roamed to a PLMN which does not support the service required by the call (as indicated in the information sent in the request for the MSRN), the VLR returns an appropriate error indication to the HLR, which relays the error indication to the interrogating exchange.

9.3 HLR Restart

If the HLR has restarted, the location information for the called MS which has been reloaded from the backup may be incorrect. In this case, the request for an MSRN is directed to the wrong VLR, but the VLR returns an MSRN and requests subscriber data from the HLR as described in Technical Specification GSM 03.07. The HLR returns the MSRN in response to the request for routeing information and the call is routed to the VMSC as described above, but the MS will not respond to paging, so the call will fail with a cause of absent subscriber, or be forwarded if Call Forwarding on MS Not Reachable is active.

Annex A (informative):
Change Request History

Change history

SMG No.

TDoc. No.

CR. No.

Section affected

New version

Subject/Comments

SMG#07

4.0.4

ETSI Publication

SMG#20

5.0.0

Release 1996 version

SMG#27

6.0.0

Release 1997 version