MCPTT server can determine to use 5G MBS for the transmission of downlink media for different types of MCPTT group calls.
The application layer signalling such as the floor control messages, application layer paging messages may be transmitted along with the MC media over the same MBS session however with different QoS requirements, or over other means such as unicast downlink or a different MBS session.
When using the procedures for pre-configured or dynamic MBS session establishment for MCPTT, the MCPTT server performs the procedure of call connect and disconnect over MBS session at the group communication session establishment phase.
Enhanced MCPTT group call setup procedure with eMBMS bearer is specified in
clause 10.10.6 of TS 23.379. When using mission critical services over 5G MBS, the application paging message transported over 5G MBS session should also be supported.
The related procedures and information flow is as specified in
TS 23.379, with only difference of using of 5G MBS session for the transmission of application paging message.
The MCPTT service shall support the procedure for using pre-created MBS session, or dynamic MBS session as specified
clause 7.3.3.1.
MCPTT may use MBS session for the different types of MCPTT group calls. Both pre-arranged group calls and chat group calls can use the pre-created 5G MBS session for distributing the media.
Both the media packets as well as the floor control messages to the receiving users are sent on the 5G MBS session. Optionally a separate 5G MBS session could be used for the floor control messages.
The MCPTT service shall support the procedure for switching between 5G MBS session, 5G unicast PDU session, LTE eMBMS bearer and LTE unicast bearer as specified in
clause 7.3.3.8 and
clause 7.3.3.9 with the following clarifications:
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The MC service client is the MCPTT client;
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The MC service server is the MCPTT server; and
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The MC service ID is the MCPTT ID.
The MCPTT service shall use the MCPTT-1, MCPTT-4, MCPTT-7, MCPTT-8 and MCPTT-9 reference points for this procedure.