4.3.6 Interaction with supplementary services

23.1723GPPRelease 17Stage 2Technical realization of Circuit Switched (CS) multimedia service UDI/RDI fallback and service modificationTS

4.3.6.1 Call forwarding and Call deflection

If CFB(UDUB), CFNRy, or Call Deflection is invoked in a SCUDIF call, and both basic services are provisioned, the HLR (for early call forwarding) or VLR (for late call forwarding) shall check the handling of the call should continue with the active service negotiated between the called UE and the network.

If call forwarding except CFB(UDUB) and CFNRy is invoked in a SCUDIF call, and both basic services are provisioned, the HLR (for early call forwarding) or VLR (for late call forwarding) shall check the service for both the preferred service and the less preferred service.

Then, the SCUDIF call interacting with call forwarding shall be handled according to the following rules:

– If the call forwarding is active only for the less preferred service, the preferred service shall be selected and the call setup shall continue with a single service without invoking call forwarding.

– If the call forwarding is active only for the preferred service, the preferred service shall be selected and call forwarding shall continue with a single service to the destination indicated by the forwarded to number.

– If the call forwarding is active for both services and the forwarded to number for the preferred service is same as for the less preferred service, the call shall continue as a SCUDIF call to the destination indicated by the forwarded to number.

– If the call forwarding is active for both services and the forwarded to number for the preferred service is different from that for the less preferred service, the preferred service shall be selected and call forwarding shall continue with a single service to the destination indicated by the forwarded to number for the preferred service.

– If the call forwarding is active for both services and CF type for the preferred service is different from that of less preferred service, the call shall continue as a SCUDIF call to the destination indicated by the forwarded to number, and the forwarding reason for the preferred service shall be indicated.

NOTE: For Late call forwarding or Call Deflection with Optimal Routing, the second basic service group code shall be generated in VMSC and sent in Resume Call Handling and may be sent in the following Send Routing Information. The preferred service is set as basic service group IE, and the less preferred service is set as basic service group 2 IE.

4.3.6.2 Closed User Group (CUG)

If a SCUDIF call interacts with CUG and both basic services are provisioned, the service state shall be checked for both the preferred service and the less preferred service. If one service is not allowed, then the call shall fall back to the allowed service.

4.3.6.3 Call barring

If a SCUDIF call interacts with call barring and both basic services are provisioned, the service state shall be checked for both the preferred service and the less preferred service. If one service is barred, then the call shall fall back to the allowed service.