7.9 Impact of GLR on CAMEL

23.1193GPPGateway Location Register (GLR)Release 17Stage 2TS

7.9.1 The VLR supports CAMEL Phase 2 onwards

When the GLR receives the MAP_UPDATE_LOCATION request message from the subscriber, the GLR checks that the CAMEL supported phase it previously received for that subscriber matches the CAMEL supported phase carried by MAP_UPDATE_LOCATION request message. If a difference is detected, the GLR relays the MAP_UPDATE_LOCATION request message to the HLR in order to obtain the proper CAMEL subscription information that corresponds to the current VLR. Refer to figure 7.9.1/1.

In order to perform this scenario, the CAMEL supported phase information needs to be added to the ‘IMSI record in GLR’ table.

It is possible that all the VLRs within a VPLMN do not support the same phase of CAMEL. This could happen in the case of an incremental upgrade of these VLRs within the VPLMN. In this case, it is possible that the HLR may receive frequent changes of the CAMEL supported phase information in the MAP_UPDATE_LOCATION request message from the GLR. The effect is that the HLR would perceive the GLR as a VLR that changes its CAMEL supported phase.

Other CAMEL related messages between HLR and VLR, e.g. Provide Subscriber Info, Provide Subscriber Info ack are always relayed transparently from the HLR to the VLR or vice versa.

Figure 7.9/1: CAMEL Subscription Information

7.9.2 The VLR supports CAMEL Phase 1 or has no CAMEL Support

If the Location Update Request message received by the GLR contains no indication that the VLR supports CAMEL, then this shows to the GLR that the VLR:

– either has no support for CAMEL.

– or supports CAMEL Phase 1.

The GLR will interpret this situation to mean that there is no CAMEL support within the VLR. Therefore the GLR will treat this as a case of an unsupported service (see clause 7.2.1.4). This will lead to an update location procedure being initiated between the GLR and HLR, causing the HLR to activate its service substitution rules.

Note the following description of a current GSM network, i.e. where there is no GLR between the HLR and VLR. When the HLR receives a Location Update request with no indication of CAMEL support, then the HLR will attempt to request CAMEL Phase 1 support in the ISD message. If the ISD is accepted by the VLR, then support for CAMEL Phase 1 is indicated. If the ISD is rejected, then no support for CAMEL Phase 1 is indicated.