scope:

The present document specifies the group management protocols needed to support Mission Critical Push To Talk (MCPTT). Group management applies only when the UE operates on the network.

Mission critical communication services are services that require preferential handling compared to normal telecommunication services, e.g. in support of police or fire brigade.

The MCPTT service can be used for public safety applications and also for general commercial applications (e.g., utility companies and railways).

The present document is applicable to User Equipment (UE) supporting the group management client (GMC) functionality, to application server supporting the group management server (GMS) functionality, and to application server supporting the MCPTT server functionality.