This document specifies the functional architecture, procedures and information flows needed to support the mission critical push to talk (MCPTT) service. The MCPTT service utilizes the common functional architecture to support MC services over LTE including the common services core defined in TS 23.280
. Support for both MCPTT group calls and MCPTT private calls operating in on-network and off-network modes of operation is specified.
The corresponding service requirements are defined in TS 22.179
and TS 22.280
The present document is applicable primarily to MCPTT voice service using E-UTRAN access based on the EPC architecture defined in TS 23.401
. Certain application functions of the MCPTT service such as dispatch and administrative functions could also be supported via non-3GPP access networks but no additional functionality is specified to support non-3GPP access.
The MCPTT service requires preferential handling compared to normal telecommunication services e.g. in support of police or fire brigade including the handling of prioritised MCPTT calls for emergency and imminent threats.
The MCPTT service can be used for public safety applications and also for general commercial applications e.g. utility companies and railways.
In the present document, MCPTT calls between MCPTT users on different MCPTT systems are considered.