Description
The Temporary MCVideo Group Identity (TGI) is a crucial identifier within the 3GPP Mission Critical Services (MCS) framework, specifically for the MCVideo service. MCVideo provides real-time group video communication for public safety, emergency services, and other mission-critical users. The TGI is a temporary, session-specific identifier assigned by the MCVideo system to a particular group call or video session. It is used to uniquely distinguish that session from all other ongoing sessions within the network for the duration of its activity. Unlike a permanent group ID (which identifies the predefined group of users), the TGI identifies the active communication instance itself.
Architecturally, the TGI is generated and managed by the core MCVideo service components, primarily the MCVideo Application Server. When an authorized user (e.g., a dispatcher or team leader) initiates a group video call, the server allocates a TGI for that session. This TGI is then disseminated to all participants' User Equipment (UE) and relevant network functions. It is used in the signaling plane to route session control messages (e.g., using SIP protocols) and in the media plane to identify the media streams associated with the call. The TGI is included in protocol messages for session establishment, modification, and termination, ensuring that all actions pertain to the correct session.
How it works involves several layers. At the service layer, the MCVideo client on a UE receives the TGI during session initiation signaling. The UE uses this TGI in all subsequent communication with the MCVideo server. In the underlying 3GPP system, the TGI may be mapped or associated with specific bearers or QoS flows to ensure the video traffic receives the appropriate priority and resources, as per the mission-critical QoS requirements. From a security perspective, the TGI is part of the security context; it can be used in key derivation for encrypting the video media, ensuring confidentiality within that specific group session. Its temporary nature is key—it is valid only for the lifetime of the call. Once the session ends, the TGI can be released and potentially reused later for a different session, aiding in resource management and preventing identifier exhaustion.
Purpose & Motivation
The TGI was created to address the specific needs of dynamic, secure, and manageable group communication in mission-critical environments. Traditional cellular group calls or conferencing systems often lacked a standardized, secure, and temporary identifier dedicated to a single session instance. Mission-critical operations require the ability to quickly spin up ad-hoc video groups, ensure communication is isolated and secure to that group, and efficiently manage multiple simultaneous ongoing incidents or operations. A permanent group identity alone is insufficient, as the same group of users may be engaged in multiple distinct video sessions (e.g., different tactical operations) concurrently.
The purpose of the TGI is to provide a handle for the system to uniquely manage each active session. It solves the problems of session disambiguation, secure media binding, and efficient routing. Historically, proprietary systems or early group communication services might have used less robust methods, leading to potential confusion or security mix-ups. The TGI, introduced as part of the standardized 3GPP MCVideo service from Release 13 onwards, provides a clean, scalable mechanism. It was motivated by the public safety community's requirements (led by organizations like TCCA and 3GPP SA6) for LTE-based mission-critical communications that are interoperable, reliable, and secure. The TGI enables features like dynamic group formation, strict access control to a specific session, and end-to-end encrypted media for that session, which are vital for law enforcement, firefighting, and emergency medical services.
Classification
Detected Changes Across Releases
from 3GPP Change RequestsSpecific changes extracted from the „Change history“ tables of 3GPP specifications (320 CRs across 5 releases). Complements the general historical overview above with the evidence-based evolution of this function.
Studied in Rel-13, normative work from Rel-15.
In Release 15, the Temporary MCVideo Group Identity (TGI) function was formally defined as a group identity representing a temporary grouping of MCVideo groups formed by the group regrouping operation. This introduction supported new procedures for remotely initiated group calls and ambient viewing, which utilize the TGI for dynamic group management.
- MCVideo ambient viewing client procedures TS 24.281CR0033
- MCVideo ambient viewing participating MCVideo function procedures and controlling MCVideo function procedures TS 24.281CR0034
- MCVideo ambient viewing general description TS 24.281CR0035
- Usage of MBMS for MCVideo - signaling control TS 24.281CR0037
- Subscription to group dynamic data TS 24.281CR0061
- Remotely initiated group call client procedures TS 24.379CR0354
+ 19 more changes
In Release 16, the Temporary MCVideo Group Identity (TGI) function was enhanced to support the creation of temporary groups via a preconfigured regroup operation, using a defined XML schema for storage and management by the MCVideo server. This allowed for automatic group affiliation and deaffiliation based on a user's location or functional alias, integrating these capabilities directly into the group regrouping procedures. Additionally, the release introduced mechanisms to check for and prevent the regrouping of groups that were already part of an existing temporary group.
- Support of functional aliases in broadcast group calls TS 24.379CR0484
- Triggering an emergency group call after an emergency alert automatically TS 24.379CR0485
- List of MCPTT group members who did not acknowledge the group call request TS 24.379CR0486
- Preconfigured regroup – XML schema for regroup using preconfigured group TS 24.379CR0529
- Additional commencement modes for group calls TS 24.379CR0542
- Automatic group affiliation and deaffiliation based on location or functional alias TS 24.379CR0541
+ 23 more changes
In Release 17, the enhancements for the Temporary MCVideo Group Identity (TGI) function included the introduction of a preconfigured regroup capability and new interconnect procedures for MCVideo Affiliation, Ambient Viewing, and Emergency Alerts. These additions expanded the operational flexibility for forming temporary groups and enabled more sophisticated cross-system group communications. The release also aligned 5GS/EPS procedures to ensure consistent TGI handling across different access networks.
- Functional Alias usage in MCVideo Call TS 24.281CR0093
- Add altitude, timestamp to MCVideo location XML schema TS 24.281CR0095
- Add preconfigured regroup to MCVideo TS 24.281CR0096
- Control per service authorizations limit for MCVideo service TS 24.281CR0100
- Check for Preconfigured Group Use Only TS 24.281CR0104
- Call control - Restricting MCVideo private communications TS 24.281CR0105
+ 93 more changes
In Release 18, the Temporary MCVideo Group Identity (TGI) function was enhanced to support general ad hoc group call procedures, including those using a pre-established session, within both single and multiple systems. These new procedures, detailed in the protocol implementation for MCVideo, expanded the operational flexibility for forming temporary groups beyond the regroup operation. Additionally, support was introduced for specific emergency ad hoc group calls and imminent peril ad hoc group calls utilizing the TGI mechanism.
- Use of 5G MBS transmission in MCVideo signalling plane TS 24.281CR0199
- Add the description of 5MBS in MCVideo TS 24.281CR0220
- MCVideo support of multiplexing - SDP offers and answers TS 24.281CR0215
- Support MCVideo over 5G ProSe TS 24.281CR0225
- General adhoc group call procedures in single system - Protoc impl for MCVideo TS 24.281CR0221
- Adhoc group call participants modify procedures in single system - protoc impl MCVideo TS 24.281CR0226
+ 107 more changes
In Release 19, enhancements for the Temporary MCVideo Group Identity (TGI) function introduced more dynamic control over ad hoc group calls and emergency alerts. Specifically, new capabilities allow authorized users to modify the participant list criteria during an ongoing MCVideo ad hoc group call or emergency alert, and to release such a call. Additionally, procedures were added to handle calls to migrated users and to prevent multiple participations in a group regroup operation.
- Modify list of participants by changing the criteria during an ongoing MCVideo ad hoc group call TS 24.281CR0278
- Adhoc group emergency alert add criteria to the SIP message containing the participant lists sent to the authorised users TS 24.281CR0279
- MCVideo adhoc group call to migrated user TS 24.281CR0280
- Modifying the criteria for determining the participants during an ongoing ad hoc group emergency alert TS 24.281CR0282
- Ad hoc group call release by an authorized user TS 24.281CR0289
- FRMCS_Ph5 Adding reason to leave a session in MCVideo TS 24.281CR0290
+ 48 more changes
Explore further
Broader topics and technologies where TGI plays a role.
Defining Specifications
3GPP specifications that define or reference TGI, with the latest known release. Sourced from the 3GPP document catalog — see methodology.
| Specification | Title | Release |
|---|---|---|
| TS 24.281 vj40 | MCVideo Signalling Control Specification | Rel-19 |
| TS 24.379 vj50 | Mission Critical Push To Talk (MCPTT) call control | Rel-19 |
| TS 36.579 | 3GPP TR 36.579 | Rel-13 |
| TS 37.579 vi40 | Mission Critical services conformance testing | Rel-18 |