MC services over a 5G system supporting EPS interworking are provided to 5GS/EPS capable MC service UEs as defined in TS 23.501, TS 23.502, and TS 23.503.
This clause describes procedures related to the support of MC services over a 5G system with EPS interworking.
As specified in TS 23.501, a dedicated user plane anchor point, i.e. UPF + PGW-U function, is defined for interworking between 5GS and EPS. This enables that the network can directly handle PDU sessions (in 5GS) and PDN connections (in EPS) associated to MC service sessions of an MC service UE during inter-system change.
The inter-system change of an MC service UE will be transparent to the MC service server. The MC service server will continue interacting with the same control plane functions, e.g. PCF, and user plane function, e.g. UPF + PGW-U.
The procedure in Figure 7.4.2-1 describes in a high level inter-system mobility of 5GS/EPS capable MC service UEs with associated MC service sessions.
Pre-conditions:
MC service UE is a 5GS/EPS capable UE.
MC service UE is registered to a 5GS supporting EPS interworking for the support of MC services.
The 5GS supporting EPS interworking decides that the MC service UE should be handed over to EPS, e.g. due to radio conditions. 5GS handles associated PDU sessions of the MC service UE to establish corresponding PDN connections in EPS, i.e. required default and dedicated EPS bearers associated to MC service sessions.
MC service UE is registered on EPS. MC services continue being provided to the MC service UE over EPS via the established PDN connections (default and dedicated bearers associated to corresponding MC service sessions) in step 2.
In the case of MC services provided over a 5GS supporting EPS interworking, the MC service server may not be able to identify whether an MC service UE is registered on 5GS or EPS. Therefore, the MC service server can subscribe/unsubscribe to receive notifications of specific events from the network. These notifications can be related to PDU sessions/PDN connections to which MC service sessions are bounded or related to a specific MC service UE or group of MC service UEs.
Such notifications can be provided from the PCF (via N5 or Rx) for specific events, e.g. access network information notification and change of access type. If SCEF+NEF is deployed, notifications can also be provided from SCEF+NEF for specific events, e.g. core network (CN) type change. The specification of these event procedures are described in TS 23.501, TS 23.502, and TS 23.503.
The procedure in Figure 7.4.3-1 describes a high level subscription/notification procedure between the MC service server and the network.
Pre-conditions:
MC service UE is a 5GS/EPS capable UE.
MC service UE is registered to a 5GS supporting EPS interworking for the support of MC services.
MC service server subscribes to receive notifications from the network associated to MC service UE related to EPS interworking events. For instance, the MC service server may subscribe to notifications of events from the PCF associated to the MC service UE, e.g. access network information notification and change of access type, as specified in TS 23.503.
If SCEF+NEF is deployed, the MC service server may also subscribe to notifications of events from SCEF+NEF associated to the MC service UE, e.g. CN type change, as specified in TS 23.501 and TS 23.502.
The 5GS supporting EPS interworking decides that the MC service UE should be handed over to EPS, e.g. due to radio conditions. 5GS handles associated PDU sessions of the MC service UE to establish corresponding PDN connections in EPS, i.e. required default and dedicated EPS bearers associated to MC service sessions.
MC service UE is registered on EPS. MC services continue being provided to the MC service UE over EPS via the established PDN connections (default and dedicated bearers associated to corresponding MC service sessions) in step 2.