5G System Learning --- MBS Session Release

1. Broadcast Session Release: In mobile communications systems, this refers to the process by which a user equipment (UE) terminates reception of broadcast signals from a 5G network, similar to ending a streaming media session. This occurs when the user explicitly terminates the session, the broadcast ends, or the device moves out of broadcast coverage. The network element (Broadcast/Multicast Service Center) will tear down the session to ensure efficient data transmission to multiple users simultaneously. Releases include:

• User-Initiated Release: The user manually stops the broadcast, similar to closing a streaming app.
• Network-Initiated Release: The broadcast session ends due to the completion of content playback or termination by the network operator. This may be due to the end of a live event or scheduled broadcast.
• Device-Initiated Release: The device moves out of broadcast coverage, resulting in signal loss and session termination.
• The Broadcast/Multicast Service Center (BM-SC) manages broadcast sessions and can initiate releases based on network policies or user actions.

2. Broadcast Session Release Process: The purpose is to release resources associated with a previously established MBS broadcast session. The release uses non-UE-associated signaling. A successful release operation is shown in Figure 8.17.3.2-1, where:

The AMF initiates this procedure by sending a Broadcast Session Release Request message to the NG-RAN node.

• Upon receipt of the Broadcast Session Release Request message, the NG-RAN node shall respond with a Broadcast Session Release Response message. The NG-RAN node shall cease broadcasting and release all MBS session resources associated with the broadcast session.
• Upon receipt of the Broadcast Session Release Response message, the AMF shall transparently transmit the Broadcast Session Release Response Transport IE (if any) to the MB-SMF.