I. MBS Service Reception A 5G terminal (UE) may be configured to receive data from an MBS multicast session only in the RRC_CONNECTED or RRC_INACTIVE state. Instead, to receive multicast services, the UE needs to perform the MBS session join procedure specified in TS 23.247 [45]. It is up to the gNB to decide whether the UE receives data from the MBS multicast session in the RRC_CONNECTED state or in the RRC_ INACTIVE state. gNB moves the UE from the RRC_CONNECTED state to the RRC_INACTIVE state by means of the RRCRelease message and from the RRC_INACTIVE state by means of the group notification or UE specific paging. INACTIVE state and moves the UE from the RRC_CONNECTED state through group notification or UE-specific paging.
II. Terminal RRC state If the UE joining a multicast session is in the RRC_CONNECTED state and when the multicast session is activated, the gNB may send an RRC Reconfiguration message to the UE with the MBS configuration related to the multicast session. If the gNB configures the UE to receive MBS multicast sessions in the RRC_INACTIVE state, the gNB may provide the PTM configuration for the MBS multicast session and information on which multicast services may continue to be received in the RRC_INACTIVE state via the RRCRelease message. the UE does not suspend the MBS services indicating that the multicast sessions continued in the RRC_INACTIVE state. MRBs for received multicast sessions. the multicast MCCH is used if the cell supports PTM updates or provides PTM configuration to UEs moving from other cells in the RRC_INACTIVE state. otherwise the presence of a multicast MCCH is optional.
III.Notification Mechanism Used to announce changes in the content of the multicast MCCH due to multicast session modification or session deactivation or due to neighboring cell information modification. The scheduling information received by the multicast MCCH will be provided via SIB24 and may also be provided via an RRCRelease message.
IV.MBS No Data Handling The gNB may move the UE to the RRC_INACTIVE state when the active multicast session has no data to be sent to the UE for the time being. When the MBS multicast session is deactivated the gNB can move the RRC_CONNECTED state UE to RRC_IDLE or RRC_INACTIVE state. For a UE receiving MBS multicast session data in the RRC_INACTIVE state, the gNB notifies the UE to stop listening to the corresponding G-RNTI-addressed PDCCH via an RRCRelease message or a multicast MCCH when there is no data to be sent for the time being, or the session has been deactivated. gNBs supporting MBS use a group notification mechanism to notify the UE in the RRC_IDLE or RRC_INACTIVE state when the CN has activated a multicast session. RRC_IDLE or RRC_INACTIVE state. gNBs that support MBS use the group notification mechanism to notify UEs in the RRC_INACTIVE state when a session has been activated and the gNB has multicast session data to be transmitted. if UEs receiving data for MBS multicast sessions that are in the RRC_INACTIVE state in the cell are notified to stop Monitoring of PDCCHs addressed by G-RNTI for all joined multicast sessions. the UE does not monitor PDCCHs addressed by multicast-MCCH-RNTI until it receives a group notification. Upon receipt of the group notification, the UE reconnects to the network or restores the connection and transitions from the RRC_IDLE state or the RRC_INACTIVE state to the RRC_CONNECTED state. Upon receipt of a group notification indicating that multicast reception is allowed in the RRC_INACTIVE state, the UE remains in the RRC_INACTIVE state and acts as specified in TS 38.331 [12]. If the UE receives notification of both the group notification and the UE specific paging, the UE follows the specific paging and enters the RRC_CONNECTED state.
V. Terminal Addressing Group notification addresses the terminal (UE) through P-RNTI on the PDCCH, and the paging channel is monitored by the UE. The paging message of the group notification contains the MBS session ID, which is used to page all UEs in the RRC_IDLE and RRC_INACTIVE states that have joined the relevant MBS multicast session, i.e., without paging the UEs individually.When the UE enters the RRC_CONNECTED state, the UE stops monitoring the group notification related to a specific multicast session, i.e., it stops checking for MBS session IDs in the paging message. Session ID. in these cases. i.e. the UE does not monitor group notifications once this UE leaves this multicast session or the network requests the UE to leave or the network releases the multicast session.
VI. Paging Terminal If a UE in the RRC_IDLE state that joins an MBS multicast session resides on a gNB that does not support MBS, the UE may receive CN-initiated paging notifications in which the CN pages each UE individually due to session activation or data availability. if a UE in the RRC_INACTIVE state that joins an MBS multicast session resides on a gNB that supports MBS, the UE may be notified individually via RAN-initiated paging due to session activation or data availability. gNB, the UE may be notified individually via RAN-initiated paging due to session activation or data availability.
NOTE: The gNB's decision to keep the UE in the RRC_CONNECTED state (e.g., in order to meet the latency requirements of a mission-critical service) or to move the UE to the RRC_INACTIVE or RRC_IDLE state (e.g., when there is no data to be sent to the UE for the time being or in order to address cell congestion) may take into account the 5QI values of the mission-critical and the non-mission-critical UEs or the other QoS parameters.
