5.5 Procedures for User Service data transfer

26.5023GPP5G Multicast-Broadcast User Service ArchitectureRelease 17TS

At the next start time indicated in the MBS User Data Ingest Session schedule of active periods, or immediately if no schedule is provisioned, the MBSF activates all MBS Distribution Sessions comprising that MBS User Data Ingest Session, as shown in figures 5.5‑1 and 5.5‑2 below.

Figure 5.5‑1: Call flow for MBS Distribution Session activation by MBSF

For each such MBS Distribution Session:

1. The MBSF invokes the Nmbstf_MBSDistributionSession_Update service operation on the MBSTF at reference point Nmb2, updating the current state of the MBS Distribution Session to ACTIVE (see step 3 in clause 4.6.1).

2. As a direct result of the previous step, the MBSTF begins to ingest content from the MBS Application Provider.

3. The MBSTF processes the ingested content according to the provisioned distribution method, as defined in clause 4.3.3. This may optionally include the computation of Application Level FEC (AL‑FEC) information.

4. The MBSTF distributes the resulting MBS data at reference point MBS‑4‑MC. This is achieved by passing the MBS data to the MB‑UPF at reference point Nmb9, according to the protocol stacks defined in clause 8.2 of TS 23.247 [5].

5. On successful content ingest and MBS data distribution, the state of the MBS Distribution Session in the MBSTF becomes and remains ACTIVE (see step 3 in clause 4.6.1); on failure, it transitions through DEACTIVATING to INACTIVE (see step 4 in clause 4.6.1).

The MBSTF invokes the Nmbstf_MBSDistributionSession_StatusNotify callback service operation at reference point Nmb2 to inform the MBSF of any changes to the state of the MBS Distribution Session.

6. The MBSF invokes the Nmbsf_MBSUserDataIngestSession_StatusNotify callback service operation at reference point Nmb10 (or Nmb5+N33, if invoked via the NEF) to inform the MBS Application Provider of any changes to the state of the MBS Distribution Session in the context of its parent MBS User Data Ingest Session.

The MBS Client in the UE activates reception of an MBS User Service by establishing an MBS User Service Session between the MBSF Client and the MBSF, and consequently activating reception of one or more MBS Distribution Sessions by the MBSTF Client that are currently being distributed by the MBSTF. This call flow is shown in figure 5.5‑2 below:

Figure 5.5‑2: Call flow for MBS User Service activation by MBS Client

The steps are as follows:

7. The MBS-Aware Application invokes a client API exposed by the MBSF Client at reference point MBS-6 to activate the MBS User Service Session.

If the MBS User Service Announcement was received by the MBS-Aware Application in step 2c in clause 5.4, this is passed as one of the parameters in the API call.

Otherwise, the target service is identified by one of the service identifiers in the MBS User Service entity (see clause 4.5.3) and this identifier is used by the MBSF Client to locate an MBS User Service Announcement obtained according to step 2a or step 2b in clause 5.4.

For each MBS Distribution Session listed in the composite MBS User Service Announcement:

8. The MBSF Client invokes a client API exposed by the MBSTF Client at reference point MBS‑6′ to activate reception of the MBS Distribution Session in question. The Session Description parameters needed to receive the MBS Distribution Session are taken from the relevant MBS Distribution Session Announcement which, in turn, is extracted from the composite MBS User Service Announcement.

9. MBS data from the MBSTF is received by the MBSTF Client at reference point MBS‑4‑MC.