Content for TS 23.247 Word version: 18.7.0

1… 4… 4.2… 4.3 5… 6… 6.6… 7… 7.1.1.2 7.1.1.3 7.1.1.4… 7.1.1.6… 7.1.2… 7.2… 7.2.2… 7.2.3… 7.2.4… 7.2.4.3… 7.2.5… 7.2.6… 7.3… 7.3.5… 7.5… 8… 9… 9.2… 9.3… 9.4… A…

4.3 Multicast session state model
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4.3 Multicast session state model p. 17

The following illustrate the states for the Multicast MBS session:

Configured state: Information about the Multicast MBS session (e.g. QoS information) is available in 5GC NFs (e.g. MB-SMF) serving the Multicast MBS session, but no User Plane resources towards NG-RAN are reserved and no MBS data can be transmitted. Only resources at MB-SMF, NEF and MB-UPF are reserved and no multicast data are transmitted. A TMGI can be allocated for the Multicast MBS session. UEs may be allowed to join (subject to authorization check and configuration), but the first accepted UE join request will trigger the Multicast MBS session establishment towards the NG-RAN and the UE, see clause 7.2.1.

NOTE 1:
The SMF is not involved in the Multicast MBS session while the Multicast MBS session is in configured state.

NOTE 2:
There may be several interim states in the configured state, e.g. TMGI requested, or information about the Multicast MBS session provided, but these interim states will not be specified in this release.
Active state: Multicast MBS session is established and MBS data can be transmitted to the UEs that have joined the Multicast MBS session. Radio resources for the Multicast MBS session are established. To receive multicast MBS session data, UEs that joined the Multicast MBS session shall be in CM-CONNECTED state for receiving data of the Multicast MBS session. UEs are allowed to join the Multicast MBS session (subject to authorization check). 5GC resources and radio resources for the Multicast MBS session are reserved for UEs that joined the Multicast MBS session.

NOTE 3:
When receiving the data of the Multicast MBS session, the joined UEs can be in CM-CONNECTED with RRC_INACTIVE state as defined in clause 6.17.
Inactive state: Multicast MBS session is established but no MBS data is transmitted to the UEs that have joined the Multicast MBS session. Radio resources for the Multicast MBS session are released, and the UEs that joined the Multicast MBS session may be in CM-CONNECTED or CM-IDLE state. UEs are allowed to join the Multicast MBS session (subject to authorization check).

The following procedures are defined which result in transition of the Multicast MBS session state:

Multicast Session Creation: The AF provides information about the Multicast MBS session and optionally requests the allocation of a TMGI, see clause 7.1.1.2 and 7.1.1.3. Alternatively, the information about the Multicast MBS session can be pre-configured in the network. The creation may indicate whether the Multicast MBS session may be established in active or inactive state and when a Multicast MBS session can become active. The AF may perform creation in several steps, e.g. to first request TMGI and then provide full information about the Multicast MBS session and allow it to be established, or to update the information whether the Multicast MBS session is to be in Active or Inactive state after establishment. Multicast MBS session state transitions from "Start (NULL)" to Configured state.

NOTE 4:
A Multicast MBS session can also be created by the operator via OAM configuration or be established without prior creation.
Multicast Session Establishment: When the join request of the first UE for the Multicast MBS session is accepted, the Multicast MBS session is established towards the NG-RAN node and the UE, see clause 7.2.1. Multicast session state transitions from "Start (NULL)" or Configured state to either Inactive or Active state.
Multicast Session Activation: See clause 7.2.5.2, Triggered by the 5GC, the radio resources for the Multicast MBS session are established and Multicast MBS session data starts to be transmitted to the UE. UEs in CM-IDLE state and CM-CONNECTED with RRC Inactive state that joined the Multicast MBS session are notified. Activation can be triggered by AF request or data notification from the MB-UPF. Multicast session state transitions from Inactive state to Active state.

NOTE 5:
The AF could not be aware, and the NEF will not be aware, whether a session is in created or established state. An AF may therefore update the session state to request the activation of a session prior to the establishment of the session, and this will determine that the session is subsequently established in Active state when the first UE joins, but will not trigger the Multicast Session Activation state transition.
Multicast Session Deactivation: See clause 7.2.5.3. Triggered by the 5GC, the radio resources for the Multicast MBS session are released and Multicast MBS session data stops to be transmitted to the UE. Deactivation can be triggered by AF request or no reception of multicast data by the MB-UPF. Multicast session state transitions from Active to Inactive state.
Multicast Session Release: Triggered by the last UE leaving the Multicast MBS session (see clause 7.2.2.2), or Multicast Session Deletion procedure (7.1.1.4 or 7.1.1.5), the resources for the Multicast MBS session are released in both 5GC nodes and RAN nodes, see clause 7.2.2. Multicast session state transitions from Active or Inactive state to Configured.
Multicast Session Deletion: All information about the Multicast MBS session is removed from the 5GC, and the TMGI for the Multicast MBS session (if allocated during Multicast Session Configuration) is deallocated, see clause 7.1.1.4 or 7.1.1.5. The deletion may be triggered by an AF request. Multicast session state transitions from Configured, Active or Inactive state to "End (NULL)".

Reproduction of 3GPP TS 23.247, Fig. 4.3-1: Multicast session states and state transitions

Figure 4.3-1: Multicast session states and state transitions

Reproduction of 3GPP TS 23.247, Fig. 4.3-2: Multicast session states and state transitions in MB-SMF

Figure 4.3-2: Multicast session states and state transitions in MB-SMF

Reproduction of 3GPP TS 23.247, Fig. 4.3-3: Multicast session states and state transitions in NG-RAN

Figure 4.3-3: Multicast session states and state transitions in NG-RAN

Reproduction of 3GPP TS 23.247, Fig. 4.3-4: Multicast session states and state transitions in SMF

Figure 4.3-4: Multicast session states and state transitions in SMF