7.5 MBS procedures for Group Message Delivery

23.2473GPPArchitectural enhancements for 5G multicast-broadcast servicesRelease 18TS

Editor’s note: The service operation and parameters are FFS, and the related steps in this clause is to be aligned with clause 9.

Editor’s note: It requires further investigation on whether the service operation should align more with T8 interface (delivery & modify) or follow the SBI design principles (CRUD).

Editor’s note: It is FFS whether TLTRI (T8 Long Term Transaction Reference ID) should be kept or use Group Message Correlation ID instead.

Editor’s note: It is FFS for the case that the service area in the request is different with the service area associated with the TMGI which is provided during the TMGI allocation.

7.5.1 Group Message Delivery via MBS Broadcast

Figure 7.5.1-1: Group Message Delivery via MBS Broadcast

NOTE 1: In the procedures referred to the TS 26.502 [18], the NEF is the MBS Application Provider.

1. The AF sends Group Message Delivery Request to the NEF, containing the Group Message Payload, MBS service area, Group Message Delivery Start Time, Stop Time, External Group Identifier.

2. The NEF checks authorization of AF. If geographical area information or civic address information was provided by the AF as MBS service area, the NEF translates the MBS service area to Cell ID list or TAI list. The NEF may further check the MBS capability within the MBS service area.

NOTE 2: The NEF is mandated for group message delivery.

3. The NEF transforms the group message payload into a file, and determines the meta data information of the file (e.g. File URL, etc.). The NEF assigns a Group Message Correlation ID that identifies this Group Message Delivery Request.

If Application Service Provisioning hasn’t been performed, step 4 to step 8 needs to be executed. Otherwise, they can be skipped.

4. The NEF performs Application Service Provisioning towards the MBSF using Object Distribution Method as specified in TS 26.502 [18], which including invoking Nmbsf_MBSUserService_Create and Nmbsf_MBSUserDataIngestSession_Create on the MBSF.

5. The MBSF performs MBS Session Creation as specified in clause 7.1.1.2 or clause 7.1.1.3.

6. The MBSF performs Distribution Session Provisioning as specified in TS 26.502 [18]. The MBSF invokes Nmbstf_MBSDistributionSession_Create on the MBSTF, passing the parameters of the MBS Distribution Session received in step 4 to the MBSTF.

7. The MB-SMF initiates the MBS Session Start for Broadcast procedure as specified in step 2 to step 9 in clause 7.3.1.

8. If the MBSF performs the service announcement, it initiates the MBS User Service Announcement as specified in TS 26.502 [18]. The application may receive the appropriate information through the MBS-6 API from the MBS Client (see TS 26.502 [18]). The NEF may receive the service announcement information via Nmbsf_MBSUserDataIngestSession_StatusNotify callback service operation (see TS 26.502 [18]).

9. The NEF sends Group Message Response to the AF, containing Group Message Correlation ID, Acceptance Status, Cause. The Acceptance Status indicates whether the group message delivery request is accepted or not. If not, the Cause indicates the appropriate failure reason. If the AF performs the service announcement, the service announcement information containing the file meta data can be optionally included in the Group Message Response. The NEF may further include the area where MBS is not supported in the Group Message Delivery response to the AF.

10. If the AF needs to perform the Service Announcement, the AF sends the application service announcement to the UE as specified in TS 26.502 [18].

11. The NEF performs the User Data Ingestion towards the MBSTF as specified in TS 26.502 [18]. The NEF may push the file to the MBSTF or let MBSTF pull the file from the NEF.

12. The MBSTF performs packetization and optionally FEC encoding as specified in TS 26.502 [18].

13. The MBSTF delivers the packets to the MB-UPF to NG-RAN, and NG-RAN broadcast to the UE as specified in step 13 to step 15 in clause 7.3.1.

14. Based on the service announcement information received in step 8 or step 10, the UE receives the packets, is required performs FEC decoding to restore the file, and gets the group message from the file, using the MBS Client as specified in TS 26.502 [18]. The MBS Client can expose the file towards the application in the UE using the MBS-7 API (see TS 26.502 [18]).

15. The NEF sends a Group Message Delivery notify to the AF, containing Group Message Correlation ID, Delivery Status. The Delivery Status indicates whether delivery of Group Message Payload corresponding is successful or not. The delivery status information is received by the NEF via Nmbsf_MBSUserDataIngestSession_StatusNotify callback service operation (see TS 26.502 [18]).

7.5.2 Modification of previously submitted Group message

Figure 7.5.2-1: Modify or Cancel Group Message Delivery via MBS Broadcast

NOTE: In the procedures referred to the TS 26.502 [18], the NEF is the MBS Application Provider.

1. The AF sends Modify Group Message Request to the NEF, containing the Group Message Correlation ID, Request Action, Group Message Payload, MBS service area, Group Message Delivery Start Time, Stop Time, External Group Identifier. The NEF identifies the associated MBS Service using the external Group Identifier. Requested Action is either set to "Modify", or "Cancel". "Modify" indicates the request is to modify the group message delivery transaction. "Cancel" indicates the request is to cancel the group message delivery transaction. The Group Message Correlation ID indicates the transaction to be modified or cancelled.

2. The NEF checks authorization of AF. If geographical area information or civic address information was provided by the AF as MBS service area, the NEF translates the MBS service area to Cell ID list or TAI list. The NEF may further check the MBS capability within the MBS service area.

If Requested Action is "Modify" and Group Message Payload is updated, step 3 to step 6 are executed:

3. The NEF transforms the group message payload into a file, and use the determined file meta data (e.g. File URL, etc.) in clause 7.5.1.

4. If the NEF pushes the updated file to the MBSTF, step 4 to step 5 can be skipped. If the MBSTF pulls the updated file from the NEF, the NEF updates MBS User Data Ingest Session on the MBSF as specified in TS 26.502 [18]. The update service operation needs to indicate an update of the file containing the updated group message.

5. The MBSF updates MBS Distribution Session on the MBSTF as specified in TS 26.502 [18]. The update service operation needs to indicate an update of the file containing the updated group message.

6. The NEF pushes the update file to the MBSTF or the MBSTF pulls the updated file from the NEF. And the MBSTF delivers the updated file towards the MB-UPF in 5GC as specified in clause 4.3.3.2 of TS 26.502 [18].

If Requested Action is "Modify" and MBS service area is updated, step 7 to step 8 are executed:

7. The NEF updates MBS User Service on the MBSF as specified in TS 26.502 [18]. The update service operation indicates MBS service area update.

8. The MBSF performs MBS Session Update as specified in clause 7.1.1.6 or clause 7.1.1.7 to update MBS service area, which triggers MBS Session Update for Broadcast as specified in clause 7.3.3.

If Requested Action is "Cancel", step 9 to step 14 are executed: step 9 to step 11 are needed when the group message delivery has started and MBSF needs to inform the MBS Client about the cancel of the file delivery. Otherwise, they can be skipped.

9. The NEF updates MBS User Data Ingest Session on the MBSF as specified in TS 26.502 [18]. The update service operation needs to indicate the cancel of the file delivery. The MBSF informs the MBS Client about the cancel of the file delivery if needed.

10. If the MBSTF pulls the file from the NEF, the MBSF updates MBS Distribution Session on the MBSTF as specified in TS 26.502 [18]. The update service operation indicates the cancel of the file delivery. The MBSTF stops the file delivery.

11. If the NEF pushes the file to the MBSTF, the NEF may send HTTP DELETE to the MBSTF to cancel the file delivery. The MBSTF stops the file delivery.

12. The NEF destroys MBS User Data Ingest Session on the MBSF as specified in TS 26.502 [18].

13. The MBSF destroys MBS Distribution Session on the MBSTF as specified in TS 26.502 [18].

14. The MBSF performs MBS Session Deletion as specified in clause 7.1.1.4 or clause 7.1.1.5, which triggers MBS Session Release for Broadcast as specified in clause 7.3.2.

15. The NEF sends Modify Group Message Response to the AF, containing Acceptance Status, Cause. The Acceptance Status indicates whether the group message request is accepted or not. If not, the Cause indicates the appropriate failure reason. The NEF may further include the area where MBS is not supported in the Group Message Delivery response to the AF.

After the modified group message is delivered, the NEF sends a Group Message Delivery to the AF as described in step 15 in clause 7.5.1.