Description
The Mission Critical User Identity (MC) is a fundamental identifier within the 3GPP-defined Mission Critical Services architecture. It is a globally unique identifier assigned to a user (e.g., a first responder) or a functional alias (e.g., 'Fire Engine 5') that is subscribed to mission-critical services. This identity is used across the entire service layer for authentication, authorization, service discovery, and session management. It is distinct from, but can be associated with, other network identities like IMSI or MSISDN, allowing mission-critical services to operate independently of the underlying access network technology (e.g., LTE, 5G).
The MC identity is a key component in the MC service framework defined in 3GPP TS 23.280 and related specifications. It is used by the Mission Critical Service client on the User Equipment (UE) to register with the MC service platform, which includes core functions like the Mission Critical Push To Talk (MCPTT) server. During registration and subsequent service requests, the MC identity is validated against the user's subscription profile stored in the Home Subscriber Server (HSS) or a dedicated Mission Critical Service database. This ensures that only authorized personnel can access critical communication groups, initiate emergency calls, or use other prioritized features.
Architecturally, the MC identity enables key service features. It supports individual and group communications, allowing users to be addressed directly or as part of a predefined talkgroup. The identity is also crucial for security, as it forms the basis for mutual authentication between the UE and the network using credentials stored on a UICC or in a soft credential system. Furthermore, it facilitates service continuity and mobility; as a user moves between cells or networks, the MC identity allows the MC service layer to maintain the user's active sessions and apply consistent policies, such as pre-emption and priority QoS, regardless of location.
In practice, the MC identity is often structured according to a specific naming convention, such as a Uniform Resource Name (URN) format defined in 3GPP TS 23.003 (e.g., 'urn:uuid:...' or a mission-critical-specific schema). This structured format allows for federation between different service providers or public safety organizations, enabling interoperability in large-scale incidents. The management of these identities, including their creation, assignment, and lifecycle, is typically handled by the mission-critical service operator's management system, which interfaces with the core network elements to provision subscription data.
Purpose & Motivation
The MC identity was created to address the specific needs of public safety and critical industry communications within commercial 3GPP networks. Traditional cellular identifiers like MSISDN (phone numbers) were designed for consumer services and lack the granularity, security, and functional requirements for mission-critical operations. There was a need for a dedicated identity that could support group-based communications, high-priority treatment, secure authentication, and interoperability across organizational and national boundaries.
Prior to its standardization, proprietary systems like TETRA or P25 used their own identity schemes, which hindered interoperability with modern IP-based LTE and 5G networks. The introduction of MC services in 3GPP Release 13 required a foundational identity mechanism that was independent of the underlying access technology, allowing mission-critical applications to be deployed over LTE and, later, 5G NR. This identity solves the problem of uniquely and securely identifying first responders and their functional roles within a standardized, scalable framework.
Furthermore, the MC identity enables the realization of key service requirements such as dynamic group management, emergency alerting, and inherent security. It provides the anchor point for applying mission-critical QoS policies, ensuring that communication sessions for authorized identities receive the necessary network resources and priority, even during network congestion. Its creation was motivated by the global push to replace or complement legacy land mobile radio (LMR) systems with broadband-based solutions, requiring a robust and standardized identity management system at the core of this transition.
Classification
Detected Changes Across Releases
from 3GPP Change RequestsSpecific changes extracted from the „Change history“ tables of 3GPP specifications (443 CRs across 6 releases). Complements the general historical overview above with the evidence-based evolution of this function.
Studied in Rel-8, normative work from Rel-15.
In Release 15, the Mission Critical (MC) user identity function was enhanced with new server-initiated procedures for group de-affiliation and regrouping, both within and across partner MC systems. It also introduced capabilities for functional alias management, defining the controlling and owning server roles, and established formal definitions for MC system interconnection, migration, and gateway servers. Furthermore, the release added specific mechanisms for MC service priority between servers, resource requests from servers, and signalling plane registration for UE migration.
- Introduction of MC server initiated group de-affiliation procedure TS 23.280CR0026
- Enhancement on group regrouping with an MC system TS 23.280CR0052
- MC server initiated group de-affiliation from group(s) in partner system TS 23.280CR0053
- FEC for mission critical services TS 23.280CR0043
- Header compression for MC services over MBMS TS 23.280CR0058
- Retrieval of migration credentials for access to SIP core / IMS of a partner MC system TS 23.280CR0066
+ 46 more changes
In Release 16, key enhancements for the Mission Critical User Identity (MC) function included the introduction of a gateway MC server for interconnection and the provision of an MC Data User IP connectivity service capability. Specific new features enabled functional alias management for interworking with LMR systems and introduced procedures for MCPTT users to leave a group call. Additionally, the release added support for location-based automatic activation/deactivation of functional aliases and expanded configuration for call forwarding in MCPTT private calls.
- Introduction of gateway MC server for interconnection TS 23.282CR0132
- MC Data User IP connectivity service capability– part 1 Functional Architecture TS 23.282CR0148
- MC Data User IP connectivity service capability– part 2 IP connectivity for Point-to-Point and Group communication TS 23.282CR0159
- Functional Alias management for interworking between MC service system and LMR system TS 23.283CR0035
- 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
+ 37 more changes
In Release 17, the Mission Critical User Identity (MC) function was enhanced to better support maritime usage by introducing a mechanism to associate a UE identity with a vessel identity. This allows a vessel itself to be identified as a UE within the 3GPP system for maritime communication services. Furthermore, the release added support for functional aliases as a called party address in MCPTT emergency private calls and expanded interworking capabilities with Land Mobile Radio (LMR) systems using functional aliases for private calls and floor control.
- Request for network resources at session establishment from the MC service server TS 23.280CR0278
- Introduction of MC service UE label for location reporting TS 23.280CR0283
- Functional alias for private call interworking between an MC service system and an LMR system TS 23.283CR0036
- Functional alias for floor control interworking between MC service system and LMR system TS 23.283CR0037
- 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
+ 77 more changes
In Release 18, the new MC User Identity function introduced the **MC gateway UE function**, which enables **MC clients residing on non-3GPP devices** and supports operations like **private call using functional alias** towards a partner MC system. Key additions include procedures for **MC gateway UE – MC client disconnection**, **MC gateway UE routing capabilities**, and enhanced support for **sharing location information across MC systems** through various models including on-demand, triggered, and subscription.
- Addition of definitions of terms and introduction related to MC gateway UE function TS 23.280CR0298
- Introduction of subclauses to capture MC gateway UE function details TS 23.280CR0299
- MCGWUE_MBMS support for MC clients residing on non-3GPP devices TS 23.280CR0301
- Using identities behind the MC gateway UE TS 23.280CR0309
- MC gateway UE routing capabilties TS 23.280CR0310
- MC gateway UE – MC client disconnection procedure TS 23.280CR0311
+ 146 more changes
In Release 19, key enhancements for the Mission Critical User Identity (MC) function included enabling the sharing of administrative configuration and user profiles between interconnected MC systems, and updating the initial UE configuration for user migration between systems. The release also introduced new procedures for modifying participant lists by changing criteria during ongoing ad hoc group emergency alerts and calls, applicable to both single and multiple interconnected MC systems. Furthermore, it defined the functional architecture for MC service logging, recording, and replay, and specified the usage of MC service group IDs for requesting specific user location information.
- Adding chapter ‘Sharing administrative configuration between interconnected MC systems’ TS 23.280CR0409
- Modify list of participants by changing the criteria during an ongoing ad hoc group emergency alert (single MC system) TS 23.280CR0413
- Changing the criteria during an ongoing ad hoc group emergency alert (multiple MC systems) TS 23.280CR0432
- Corrections to MC service emergency alert cancel request information flow TS 23.280CR0469
- ACM providing interconnection MC service group ID TS 23.280CR0506
- ACM updating MC service UE initial configuration for migration TS 23.280CR0508
+ 93 more changes
In Release 20, key enhancements for the Mission Critical User Identity (MC) function included the provision of a User Info ID during the MC service user authentication procedure to improve identification. The release also introduced specific procedures for call forwarding within Ad hoc Group calls, both for single MCPTT systems and those involving multiple systems. Furthermore, it added support for MC gateway UE migration and updated configurations to allow for the preconfigured regrouping of ad hoc groups for MCPTT services.
- Functional model for MC service UE disable and enable TS 23.280CR0709
- 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
- Provide User Info ID during MC service user authentication procedure TS 23.280CR0708
- MC gateway UE migration support TS 23.280CR0724
+ 8 more changes
Explore further
Broader topics and technologies where MC plays a role.
Defining Specifications
3GPP specifications that define or reference MC, with the latest known release. Sourced from the 3GPP document catalog — see methodology.
| Specification | Title | Release |
|---|---|---|
| TS 22.119 vj00 | Maritime Communication Service Requirements | Rel-19 |
| TS 23.180 vj10 | MC services support in IOPS mode | Rel-19 |
| TS 23.280 vk10 | Common Architecture for Mission Critical Services | Rel-20 |
| TS 23.281 vk10 | MCVideo Functional Architecture and Flows | Rel-20 |
| TS 23.282 vk00 | MCData Functional Architecture & Info Flows | Rel-20 |
| TS 23.283 vk00 | Mission Critical Communication Interworking | Rel-20 |
| TS 23.379 vk00 | MCPTT Functional Architecture | Rel-20 |
| TS 23.700 vk00 | XR Services Application Enablement Layer | Rel-20 |
| TR 23.783 vi00 | Technical Report on Mission Critical Services over 5GS | Rel-18 |
| TS 23.784 vg00 | Discreet Listening for Mission Critical Services | Rel-16 |
| TS 23.790 vf00 | FRMCS Gap Analysis and Architecture Enhancements | Rel-15 |
| TS 24.281 vj40 | MCVideo Signalling Control Specification | Rel-19 |
| TS 24.282 vj50 | MCData Signalling Control Protocols | Rel-19 |
| TS 24.379 vj50 | Mission Critical Push To Talk (MCPTT) call control | Rel-19 |
| TS 24.482 vj00 | Mission Critical Services Identity Management | 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 26.110 vj00 | 3G-324M Multimedia Codecs for Circuit Switched Networks | Rel-19 |
| TS 26.255 vj00 | IVAS Frame Loss Concealment Procedure | Rel-19 |
| TS 26.281 vj00 | MCVideo Codecs and Media Handling | Rel-19 |
| TR 26.865 vi00 | Technical Report | Rel-18 |
| 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 |
| TS 29.379 vj00 | MCPTT call control interworking with LMR systems | Rel-19 |
| TS 33.107 vj00 | Lawful Interception Architecture & Functions | 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 33.880 vf10 | Security Study for Enhanced Mission Critical Services | Rel-15 |
| TS 37.145 vj10 | AAS Base Station Conducted Conformance Testing | Rel-19 |
| TS 37.579 vi40 | Mission Critical services conformance testing | Rel-18 |
| TS 37.802 va10 | MSR BS RF Requirements for Non-Contiguous Spectrum | Rel-10 |
| TR 37.900 vj00 | Multi-Standard Radio (MSR) Base Station Requirements | Rel-19 |