13.6.5 Retrieval of the held call, ongoing call is on-hold/completed

23.2843GPPLocal Call Local Switch (LCLS)Release 17Stage 2TS

13.6.5.1 General Principle

When the UE requests to place the new call on hold and retrieve the original call, the MSC server shall initiate normal call hold procedures as described in clause 13.6.1 for the new call. The MSC server sends the ASSIGNMENT REQUEST message with the GCR and LCLS-Configuration of the original call to the BSS. The MSC server continues the retrieval procedure as described in clause 13.6.2.2.

When the UE requests to retrieve the original call after the active session has completed, the MSC server shall send the ASSIGMENT REQUEST message to the BSS to update the GCR and LCLS-Configuration for the original call. The MSC server continues the retrieval procedures as described in clause 13.6.2.2.

13.6.5.2 Example call flow, Retrieval of held call after ongoing call has completed

Figure 13.6.5.2.1: Retrieval of held call, ongoing call has completed

1. The active session between UE-A and UE-C is released.

2. The RETRIEVE message is sent from UE-A to MSC-A Server.

3. MSC-A server accepts the RETRIEVE request.

4. MSC-A server retrieves the LCLS-Configuration and GCR for the held session and sends the ASSIGNMENT REQUEST message to BSS-A including the LCLS-Configuration IE and the GCR IE.

5. The BSS-A returns the ASSIGNMENT COMPLETE message with the LCLS-BSS-Status IE indicating "call not possible to be locally switched".

6. MSC-A server continues the sequence handling described in clause 13.6.2.3.2.