An MBS session is established as described in in TS 23.247
(either a multicast or a broadcast session), and associated with a certain active VAL service group for group communication purposes. In the case of a multicast MBS session, the NRM clients have already joined the session.
The VAL server invoke the multicast resource update request to the NRM server once the need has emerged to modify some aspects for the given MBS session under consideration. The updated parameters are included, e.g., service requirements, service area or both. In case of multicast MBS sessions, the VAL server may as well include the status (active or inactive) of the multicast MBS session to be set.
The NRM server performs an MBS session update procedure with the 5GC as described in 3GPP 23.247 . Based on the needed requirements, the corresponding MBS session is accordingly modified at the 5GS. The update may lead to QoS Flow(s) addition, modification, or removal. The NRM server receives an MBS session update response once the requested modifications are performed, and the indicated MBS session is updated accordingly.
The NRM server may initiate a session announcement towards the NRM clients associated with the ongoing session in order to announce the updated information, if required, e.g., the updated service area or SDP information.
The NRM server sends an MapGroupToSessionStream over the configured MBS session providing the required information to receive the media related to the established VAL service group communication.
The NRM clients process the received information over the MapGroupToSessionStream in order to receive the associated VAL media over the specific MBS session stream.
The NRM server returns the multicast resource update resonse to the VAL server.
VAL client 1 sends media to the VAL server over unicast to be distributed for the established group communication.
The VAL server distributes the VAL media to the VAL clients 2 to n over the indicated streams.