Content for  TS 23.434  Word version:  19.4.2

This subclause defines information flows and procedures for 5G MBS usage that applies to VAL services. 5G MBS session can be used by any VAL service for any VAL service group. The main purpose of using 5G Multicast-Broadcast Service (MBS) by verticals is to provide efficient downlink delivery of user traffic in VAL service group communications or in a certain area. Multicast and broadcast communication services in 5G for vertical applicationsrely on the creation and establishment of MBS sessions to deliver user data in downlink. Shared and individual delivery from the VAL server to multiple VAL users is supported either as point-to-point or point-to-multipoint over the radio. The MBS session which consist of one or multiple QoS flows for different service requirements are either broadcast or multicast type. For the broadcast MBS session or local MBS session, the MBS service area is configured with the MBS session. Within this arrangement, the VAL server decides whether to create broadcast or multicast MBS sessions to be associated with certain VAL service groups or area. The 5GC adaptively decides whether to deliver the MBS traffic from the MB-UPF in the form of shared delivery or individual delivery, where the latter is applicable to multicast MBS sessions. The NG-RAN decides to utilize point-to-point or point-to-multipoint delivery methods applicable for shared delivery only. MBS provides reliability enhancements and minimizes loss of information, e.g., due to mobility and handover. MBS group scheduling mechanism enables simultaneous reception of MBS and unicast user traffic by the VAL UEs. The UEs can receive broadcast MBS sessions irrespective of their RRC state (i.e., connected, inactive or idle) and multicast sessions in RRC-CONNECTED state and RRC_INACTIVE state. The following capabilities (non-exhaustive list) provided by MBS could be used by NRM server:

• MBS session creation;
• MBS session update;
• MBS session release;
• MBS session ID allocation;
• Dynamic PCC control for MBS session.

The first phase to utilize MBS sessions for VAL media transmission is to reserve the network resource by creating a MBS sessions. The MBS session creation is initiated by the VAL server towards the NRM server, and the NRM server further interacts with the 5GS to complete the whole process. The UE's capabilities and service related information e.g., UE's MBS capabilities, location, MBS listening status report, UE session join notification sent by group members are considered when deciding to create or use MBS sessions. During the interaction with NRM server, the necessary information related to the requested session is determined, e.g., MBS session mode (either a broadcast or a multicast session) and the required service profile. This interaction between the NRM server and the 5GS depends on the configuration option under consideration, i.e., whether the NRM server is in trusted domain (limited operations), and whether the session creation is done with or without a dynamic PCC rule. The information elements describing the MBS session under consideration is then sent to the NRM clients via MBS session announcement, where the latter need to react according to the announced session mode. If eMBMS and 5G MBS co-exist for VAL services, the NRM service server may decide to trigger the establishment of an eMBMS bearer to deliver the VAL media associated to the VAL service group communications, if the target VAL service group(s) consists of members with MBMS capable RAT. As a result, the NRM server subsequently needs to send an eMBMS bearer announcement towards the clients camping on LTE.