4 Introduction

23.3793GPPFunctional architecture and information flows to support Mission Critical Push To Talk (MCPTT)Release 18Stage 2TS

The MCPTT service supports communication between several users (i.e. group call), where each user has the ability to gain access to the permission to talk in an arbitrated manner. The MCPTT service also supports private calls between two users.

The MCPTT architecture utilises the common functional architecture to support mission critical services over LTE defined in 3GPP TS 23.280 [16] and aspects of the IMS architecture defined in 3GPP TS 23.228 [5], the Proximity-based Services (ProSe) architecture defined in 3GPP TS 23.303 [7], the Group Communication System Enablers for LTE (GCSE_LTE) architecture defined in 3GPP TS 23.468 [9] and the PS-PS access transfer procedures defined in 3GPP TS 23.237 [6] to enable support of the MCPTT service.

The MCPTT UE primarily obtains access to the MCPTT service via E-UTRAN, using the EPS architecture defined in 3GPP TS 23.401 [8]. Certain application functions of MCPTT service such as dispatch and administrative functions can be supported using either MCPTT UEs in E-UTRAN or using MCPTT UEs via non-3GPP access networks.

NOTE: Dispatch consoles and devices used by MCPTT service administrators are considered MCPTT UEs in the MCPTT architecture.

MCPTT UEs that use non-3GPP access can only support a subset of the functionality specified in this specification that is supported by the non-3GPP access network.

The MCPTT system provides the function to support interworking with LMR systems defined in 3GPP TS 23.283 [20].