Description
The Mission Critical Push to Talk Identity (MCPTT ID) is a core element within the 3GPP Mission Critical Services (MCS) architecture, specifically defined for the MCPTT service. It serves as a unique, persistent identifier assigned to an MCPTT user (e.g., a first responder) or an MCPTT group. This identity is used throughout the service layer for authentication, authorization, service provisioning, and routing of push-to-talk communications. The MCPTT ID is distinct from, but can be associated with, other 3GPP identifiers like IMSI or MSISDN, and it is managed within the MCPTT service's home network.
Architecturally, the MCPTT ID is utilized by several functional entities defined in 3GPP specifications. The MCPTT client, residing on the user equipment (UE), is configured with this identity. During registration, the MCPTT client presents the MCPTT ID to the MCPTT service platform, which includes components like the MCPTT Server, MCPTT Application Server, and key management entities. The identity is validated against subscription data stored in the Home Subscriber Server (HSS) or a dedicated MCPTT database. For group communications, MCPTT Group IDs are used to define talkgroups, and the MCPTT ID determines a user's membership and privileges within those groups (e.g., dispatcher, floor control rights).
How it works involves the identity being embedded in signaling messages (using protocols like SIP and HTTP) for all MCPTT procedures: registration, group affiliation, call initiation (floor request), and emergency calls. Security is paramount; the MCPTT ID is a key input for authentication and key agreement procedures, ensuring that only authorized users can access the service. It also enables features like identity-based priority and pre-emption, where a high-priority user's MCPTT ID can grant them immediate access to network resources during congestion. The identity remains consistent across sessions and is crucial for lawful interception and logging for public safety accountability.
Purpose & Motivation
MCPTT Identity was created to fulfill the stringent requirements of professional and public safety communications migrating from legacy Land Mobile Radio (LMR) systems like TETRA or P25 to 3GPP-based broadband networks (LTE, 5G). Legacy systems had their own proprietary identity and security models. A standardized, secure identity framework was necessary to enable interoperability between different vendors' MCPTT solutions and to allow public safety users to roam onto visited networks while maintaining their service profile and authorization.
The limitations of using generic cellular identifiers (like phone numbers) for mission-critical services were significant. These identifiers lacked the granularity for group management, did not inherently support service-specific authentication, and could not easily encode user roles or priorities. The MCPTT ID solves these problems by providing a service-layer identity specifically tailored for push-to-talk. It enables secure, authenticated access to the MCPTT service, supports dynamic group management, and forms the basis for advanced features like emergency alerting, inherent user priority, and secure end-to-end group communications. Its creation was motivated by the need for a reliable, standardized, and secure identity mechanism that is integral to making LTE/5G a viable replacement for traditional PMR networks.
Release Timeline
Detected Changes Across Releases
from 3GPP Change RequestsSpecific changes extracted from the „Change history“ tables of 3GPP specifications (300 CRs across 6 releases). Complements the general historical overview above with the evidence-based evolution of this function.
In Release 15, key enhancements for the Mission Critical Push to Talk (MCPTT) identity function included the formal definition of the MCPTT-3 functional model for interconnection, which supports specific group configurations between systems. The release also introduced new procedures for managing functional aliases, distinguishing between the MCPTT server serving the user and the one owning the alias, and added an implicit floor request Information Element (IE) to MCPTT emergency group call requests. Furthermore, it standardized the MCPTT call end response message and refined numerous flows and terminologies, such as renaming "MCPTT emergency state cancel" and updating the emergency alert for multicast.
- MCPTT unicast media flow stop and resume TS 23.379CR0044
- Functional model for MCPTT interconnection TS 23.379CR0079
- MCPTT specific group configuration for interconnection TS 23.379CR0114
- Definition of MCPTT-3 TS 23.379CR0119
- Managing functional alias – MCPTT server serving the user TS 24.379CR0390
- Managing functional alias – MCPTT server owning the functional alias TS 24.379CR0391
+ 29 more changes
In Release 16, key enhancements for MCPTT Identity included new configuration and procedures for functional alias management, such as automatic activation and deactivation based on location and implicit activation settings. It also introduced features for call management, including call forwarding for MCPTT private calls and a procedure for a user leaving a group call. Furthermore, the release added capabilities for monitoring group call participation, specifically providing a list of MCPTT group members who did not acknowledge a group call request.
- Move interworking of functional alias from MCPTT to MCCoRe TS, MCPTT part TS 22.179CR0068
- Move interworking of functional alias from MCPTT to MCCoRe TS, MCCoRe part TS 22.280CR0094
- Provide list of MCPTT group members who did not acknowledge the group call request TS 23.379CR0191
- User configuration for functional alias information query for MCPTT TS 23.379CR0195
- MCPTT configuration for implicit functional alias activation/deactivation TS 23.379CR0203
- Add configuration for call forwarding for MCPTT private calls TS 23.379CR0210
+ 28 more changes
In Release 17, key enhancements for MCPTT included new call management features for private calls such as call transfer, announced call redirection, and call forwarding based on manual input, including the ability to use functional aliases as the target address. The release also added altitude and accuracy details to the MCPTT location XML schema and introduced comprehensive interconnect procedures for MCPTT Gateway Servers, covering pre-arranged groups, affiliation, chat groups, and remote group management. Furthermore, it specified enhancements for interworking MCPTT group calls with GSM-R systems.
- Add enhancements for interworking of MCPTT group calls with GSM-R TS 23.283CR0049
- Support of functional aliases as called party address in MCPTT emergency private calls TS 23.379CR0225
- Add call transfer for MCPTT private calls TS 23.379CR0229
- Add announced call redirection for MCPTT private calls TS 23.379CR0246
- Add call forwarding based on manual input for MCPTT private calls TS 23.379CR0247
- Add call forwarding based on manual input for MCPTT private calls TS 23.379CR0249
+ 67 more changes
In Release 18, key enhancements for MCPTT included expanded support for **ad hoc group call procedures** both within a single system and across multiple MCPTT systems, with new capabilities for modifying participant lists during ongoing calls. It introduced features for **private call forwarding and transfer between several MCPTT systems**, and added configuration to allow users to restrict the dissemination of their location information. Furthermore, the release enabled **auto-affiliation to MCPTT groups** for remotely initiated calls and integrated support for **5G MBS inter-RAT information** in MCPTT signalling.
- Preconfigured regrouping support for MCPTT TS 23.280CR0366
- Allow the user to restrict the dissemination of the location information – MCPTT Configuration TS 23.379CR0308
- Auto affiliate to MCPTT group for remotely initiated MCPTT call request procedure TS 23.379CR0309
- Private call forwarding between several MCPTT systems TS 23.379CR0310
- Private call transfer between several MCPTT systems TS 23.379CR0313
- Ad hoc group call procedures in single MCPTT system TS 23.379CR0324
+ 97 more changes
In Release 19, the MCPTT function introduced enhanced procedures for managing dynamic ad hoc group calls, including the ability for authorized users to modify the participant list by changing the selection criteria during an ongoing call. It also added new configuration options for authorizing modifications to emergency alert participants within an ad hoc group and introduced a specific procedure for an authorized user to release an ad hoc group call. Furthermore, the release included features for MCPTT control plane and user plane separation and provided configurations for targeting specific MCPTT users for recording.
- Clarifications on temporary and pre-arranged MCPTT broadcast groups TS 23.379CR0357
- Modify list of participants by changing the criteria during an ongoing MCPTT ad hoc group call (single MC system) TS 23.379CR0360
- Changing the criteria during an ongoing MCPTT ad hoc group call (multiple MC systems) TS 23.379CR0372
- Configuration for authorising modification of ad hoc group emergency alert participants - mcptt TS 23.379CR0391
- Adhoc group call release by an authorized user (MCPTT) TS 23.379CR0402
- Change list of participants when criteria was used to setup the ad hoc group call (MCPTT) TS 23.379CR0401
+ 41 more changes
In Release 20, the MCPTT function introduced new procedures for call forwarding specifically for Ad hoc Group calls, both within a single system and involving multiple MCPTT systems. It also added support for interworking of emergency alerts initiated by MCPTT users in ad hoc groups and allowed configurations for preconfigured ad hoc group regroup. Furthermore, the release provided mechanisms for authorizing requests for MCPTT client connection quality and included clarifications and corrections to server-to-server messaging and terminology.
- Interworking support for ad hoc group emergency alerts (MCPTT user initiated) TS 23.283CR0091
- Call forwarding for Ad hoc Group calls single MCPTT system (procedures) TS 23.379CR0489
- Call forwarding for Ad hoc Group calls involving multiple MCPTT systems (procedures) TS 23.379CR0490
- Configurations update to allow preconfigured ad hoc group regroup for MCPTT TS 23.379CR0519
- Authorisation to request quality of connection of MCPTT client TS 23.379CR0520
- Resolving Editor’s Notes on server-to-server messages (MCPTT) information flows TS 23.379CR0503
+ 2 more changes
Explore further
Broader topics and technologies where MCPTT plays a role.
Defining Specifications
3GPP specifications that define or reference MCPTT, with the latest known release. Sourced from the 3GPP document catalog — see methodology.
| Specification | Title | Release |
|---|---|---|
| TS 22.179 vk00 | MCPTT Service Requirements | Rel-20 |
| TS 22.280 vk00 | Mission Critical Services Common Requirements | Rel-20 |
| TS 22.281 vj00 | Mission Critical Video (MCVideo) Service Requirements | Rel-19 |
| TR 22.879 ve00 | Mission Critical Video over LTE Feasibility Study | Rel-14 |
| TS 22.880 ve00 | Mission Critical Data Communications Study | Rel-14 |
| TS 23.179 vd50 | MCPTT Functional Architecture | Rel-13 |
| TS 23.280 vk10 | Common Architecture for Mission Critical Services | Rel-20 |
| TS 23.283 vk00 | Mission Critical Communication Interworking | Rel-20 |
| TS 23.379 vk00 | MCPTT Functional Architecture | Rel-20 |
| TS 23.479 vj00 | MBMS API for Mission Critical Services | Rel-19 |
| TS 23.700 vk00 | XR Services Application Enablement Layer | Rel-20 |
| TS 23.741 vd00 | MBMS/GCSE_LTE Architecture Enhancements Study | Rel-13 |
| TR 23.780 ve00 | MBMS for Mission Critical Communication Services | Rel-14 |
| TR 23.781 vf00 | Study on MC services migration & interconnection | Rel-15 |
| TS 23.782 vf00 | Interworking between LTE MC and non-LTE MC systems | Rel-15 |
| TR 23.783 vi00 | Technical Report on Mission Critical Services over 5GS | Rel-18 |
| TS 23.790 vf00 | FRMCS Gap Analysis and Architecture Enhancements | Rel-15 |
| TS 23.792 vg00 | MBMS API for Mission Critical Services | Rel-16 |
| TS 24.229 vj50 | IMS call control protocol based on SIP and SDP | Rel-19 |
| TS 24.379 vj50 | Mission Critical Push To Talk (MCPTT) call control | Rel-19 |
| TS 24.380 vj10 | MCPTT Media Plane Control Protocol | Rel-19 |
| TS 24.481 vj20 | Mission Critical Services (MCS) group management | Rel-19 |
| TS 24.482 vj00 | Mission Critical Services Identity Management | Rel-19 |
| TS 24.483 vj20 | Mission Critical Services Management Object | Rel-19 |
| TS 24.484 vj30 | MCS Configuration Management | Rel-19 |
| TS 24.883 vg00 | MCPTT Interworking with LMR Systems | Rel-16 |
| TR 24.980 vg00 | MCPTT IMS Profile for Gm Reference Point | Rel-16 |
| TS 26.179 vj00 | Codecs and Media Handling for MCPTT | Rel-19 |
| TS 26.281 vj00 | MCVideo Codecs and Media Handling | Rel-19 |
| TS 26.346 vj20 | MBMS User Services Media Codecs & Protocols | Rel-19 |
| TS 26.802 vj20 | Multicast Enhancements for 5G Media Streaming | Rel-19 |
| TS 26.880 ve00 | MBMS Enhancements for Mission Critical Video | Rel-14 |
| TS 26.881 vf00 | MBMS FEC for Mission Critical Services Study | Rel-15 |
| TR 26.928 vj00 | Study on eXtended Reality (XR) in 5G | Rel-19 |
| TR 26.989 vj00 | MCPTT Enhancement Analysis | Rel-19 |
| TS 29.165 vj10 | Inter-IMS Network to Network Interface (NNI) | Rel-19 |
| TS 29.379 vj00 | MCPTT call control interworking with LMR systems | Rel-19 |
| TS 29.380 vj00 | MCPTT-LMR Interworking Media Plane Control | Rel-19 |
| TS 29.514 vj40 | 5G System; Policy Authorization Service; Stage 3 | Rel-19 |
| TS 31.102 vj40 | USIM Application Specification | Rel-19 |
| TS 31.103 vj00 | ISIM Application Specification | Rel-19 |
| TS 33.107 vj00 | Lawful Interception Architecture & Functions | Rel-19 |
| TS 33.108 vj00 | LI Handover Interface Specification | Rel-19 |
| TS 33.126 vj30 | Lawful Interception Requirements | Rel-19 |
| TS 33.127 vj50 | Lawful Interception Architecture and Functions | Rel-19 |
| TS 33.128 vj50 | 3GPP TS 33.128: Lawful Interception Protocols | Rel-19 |
| TS 33.179 vdc0 | MCPTT Security Architecture and Procedures | Rel-13 |
| TS 33.180 vk00 | Security of Mission Critical (MC) Service | Rel-20 |
| TS 33.879 vd10 | MCPTT Security Study | Rel-13 |
| TS 33.880 vf10 | Security Study for Enhanced Mission Critical Services | Rel-15 |
| TS 36.331 vj00 | LTE RRC Protocol Specification | Rel-19 |
| TS 36.579 | 3GPP TR 36.579 | Rel-13 |
| TS 37.579 vi40 | Mission Critical services conformance testing | Rel-18 |
| TR 38.913 vj00 | Next Gen Access Tech Scenarios & Requirements | Rel-19 |
