6a.5 Collaborative Session release

23.2373GPPIP Multimedia Subsystem (IMS) Service ContinuityRelease 17Stage 2TS

Tools: ARFCN - Frequency Conversion for 5G NR/LTE/UMTS/GSM

6a.5.1 Controller UE Initiated Release Collaborative Session

The following information flow shows the Controller UE releasing a Collaborative Session to release all the media flows with remote party. As a pre-requisite, there exists a Collaborative Session with two media flows, Media Flow–A on the Controller UE (UE-1) and Media Flow–B on the Controllee UE (UE-2).

Figure 6a.5.1-1: Controller UE initiated Collaborative Session release

1. UE-1 sends a Release Collaborative Session request to the SCC AS to release the Collaborative Session and to release the Media Flow-B on UE-2: UE-1 removes Media Flow-A that is participating in the Collaborative Session.

2. The SCC AS identifies the Collaborative Session and the participating Access Leg from Controllee UE. SCC AS sends the Release Access Leg request to UE-2. The request identifies the Access Leg that needs to be released.

3. UE-2 releases the Access Leg and sends back Release Access Leg response to SCC AS.

4. The SCC AS releases the Remote Leg using IMS session release procedure as specified in TS 23.228 [4].

5. The SCC AS sends Release Collaborative Session response to UE-1.

6a.5.2 Remote Party Initiated Release Collaborative Session

The following shows the information flow where the remote party initiates the release of the session, which causes the SCC-AS to release the Collaborative Session.

UE-1 is a Controller UE and the other UEs are Controllee UEs.

Figure 6a.5.2-1: Remote Party Initiated Release Collaborative Session

1. The Remote Party decides to release the session, and therefore a Session Release Request is sent by the remote party to the SCC-AS.

2. The SCC-AS releases the Access Leg(s) towards the Controller UE-1.

3. The SCC-AS releases the Access Leg(s) towards the different Controllee UEs. This occurs in parallel with step 2.

4. When all Access Legs that belonged to the Collaborative Session have been released, the SCC-AS responds to the remote party.