Description
The MCPTT Imminent peril Group (MIG) is a specialized functional group defined within the 3GPP Mission Critical Services (MCS) architecture, specifically for the Mission Critical Push-To-Talk (MCPTT) service. An Imminent peril Group is a pre-configured or dynamically created group of MCPTT users established for the purpose of managing communications during a situation of imminent danger or threat to life. The group is characterized by its association with an imminent peril condition, which triggers specific high-priority behaviors within the MCPTT system.
Architecturally, the MIG is a logical entity managed by the MCPTT application server. Its definition and membership are stored and controlled within the MCPTT service framework. Key network components involved include the MCPTT client on user equipment, the MCPTT application server, and the underlying 3GPP core network (EPC or 5GC) which provides the prioritized bearer and QoS mechanisms. The group is identified by a unique MCPTT Group ID and is associated with metadata indicating its status as an Imminent peril Group.
How it works involves both configuration and dynamic operation. A MIG can be statically provisioned by an administrator or created dynamically by an authorized user (e.g., an incident commander) when a perilous situation arises. When activated or used, communications within the MIG are typically granted the highest possible priority. This includes pre-emptive access to the floor for talker arbitration, guaranteed QoS for media bearers to minimize latency and packet loss, and potential prioritization over other network traffic. The MCPTT server ensures that calls to or from the MIG are handled with minimal setup time and that participants receive clear indications of the group's imminent peril status. Its role is to provide an unambiguous, high-assurance communication channel that takes precedence during critical incidents, directly supporting life-saving operations.
Purpose & Motivation
The MIG concept was created to address a critical shortfall in general-purpose group communication systems: the inability to guarantee absolute priority and reliability for communications during genuine life-threatening emergencies. In public safety and mission-critical operations, situations arise where personnel are under immediate physical threat (e.g., officer down, firefighter trapped, chemical hazard release). Standard communication channels can become congested or subject to contention, causing dangerous delays.
It solves the problem of ensuring that emergency communications can pre-empt all other traffic, both within the MCPTT service and within the radio access and core network. Prior to its standardization in 3GPP, similar concepts existed in legacy Land Mobile Radio (LMR) systems (e.g., emergency group calls), but these were not integrated with LTE/5G QoS frameworks. MIG provides a standardized, network-aware mechanism that leverages 3GPP's sophisticated priority and pre-emption capabilities (e.g., QoS Class Identifier, Allocation and Retention Priority) end-to-end.
The motivation for its introduction in 3GPP Release 13 was the development of full MCPTT specifications to replace or complement LMR systems. It addresses the stringent requirements of public safety users who must have confidence that their most critical communications will always get through. The MIG ensures that during an imminent peril event, the necessary network resources are dedicated and protected, minimizing any risk of communication failure when it matters most.
Classification
Detected Changes Across Releases
from 3GPP Change RequestsSpecific changes extracted from the „Change history“ tables of 3GPP specifications (202 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 MCPTT Imminent Peril Group (MIG) function was introduced, which includes the definition of the "in-progress imminent peril group state" and the associated "MCPTT imminent peril group call state" from the client's perspective. This release also introduced specific procedures for managing these states, including corrections to the TPF (Talker Priority and Floor control) procedures for imminent peril calls to ensure proper call handling. Furthermore, the release added capabilities for the remote initiation of group calls and subscription to group dynamic data, which support the operational context of imminent peril scenarios.
- Remotely initiated group call client procedures TS 24.379CR0354
- Remotely initiated group call server procedures TS 24.379CR0355
- Managing functional alias – MCPTT server serving the user TS 24.379CR0390
- Managing functional alias – MCPTT server owning the functional alias TS 24.379CR0391
- Subscription to group dynamic data TS 24.379CR0432
- Corrections to mcpttinfo.xsd TS 24.379CR0383
+ 6 more changes
In Release 16, key enhancements for the MIG function included the ability to automatically trigger an emergency group call following an emergency alert and to allow such imminent peril calls even when a user has reached their maximum number of simultaneous sessions. The release also introduced subsequent corrections to the procedures for upgrading calls to an emergency or imminent peril state, refining the overall reliability of the function.
- 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
+ 17 more changes
In Release 17, the MCPTT Imminent Peril Group (MIG) function was enhanced through the introduction of interconnect procedures, enabling coordinated emergency operations between different MCPTT systems. These new procedures include specific capabilities for MCPTT emergency alerts, group regroup, and user regroup across interconnected systems. This allows for the formation and management of temporary MCPTT group identities during imminent peril situations, facilitating mutual aid between trusted or untrusted partner networks.
- Add altitude, timestamp to MCPTT location XML schema TS 24.379CR0625
- Check for Preconfigured Group Use Only TS 24.379CR0626
- Call transfer for MCPTT private call, call control part TS 24.379CR0673
- Add accuracy to MCPTT location XML schema TS 24.379CR0698
- Call forwarding for MCPTT private call, call control part TS 24.379CR0709
- Interconnect - MCPTT Gateway Server functional entity TS 24.379CR0720
+ 54 more changes
In Release 18, the MIG (MCPTT Imminent Peril Group) function was enhanced with support for emergency and imminent peril adhoc group calls, including specific procedures for initiating such calls. The release also introduced the ability for an MCPTT client to subscribe to participant information for an ongoing adhoc group call. Furthermore, location requests from an MCPTT client were extended to support the use of a functional alias.
- MCPTT Chat group join to group regroup TS 24.379CR0855
- Addition of 5G MBS inter-RAT information in MCPTT signalling TS 24.379CR0873
- MC GW UE functions in MCPTT TS 24.379CR0901
- General adhoc group call procedures in single system - Protoc impl for MCPTT TS 24.379CR0902
- Add the description of 5MBS in MCPTT TS 24.379CR0899
- Support MCPTT over 5G ProSe TS 24.379CR0905
+ 66 more changes
In Release 19, enhancements for the MCPTT Imminent Peril Group (MIG) function included modifications to the criteria for determining participants during an ongoing ad hoc group emergency alert and the addition of criteria to the SIP message containing participant lists for authorized users. The release also introduced corrections and clarifications for procedures such as ad hoc group call setup and the handling of ad hoc group emergency alert cancellation.
- Modify list of participants by changing the criteria during an ongoing MCPTT ad hoc group call TS 24.379CR1004
- Adhoc group emergency alert add criteria to the SIP message containing the participant lists sent to the authorised users TS 24.379CR1014
- MCPTT adhoc group call to migrated user TS 24.379CR1015
- Adding option to apply automatic commencement for adhoc group calls TS 24.379CR1021
- Modifying the criteria for determining the participants during an ongoing ad hoc group emergency alert TS 24.379CR1018
- Adhoc group call release by an authorized user (MCPTT) TS 24.379CR1022
+ 29 more changes
Explore further
Broader topics and technologies where MIG plays a role.
Defining Specifications
3GPP specifications that define or reference MIG, with the latest known release. Sourced from the 3GPP document catalog — see methodology.
| Specification | Title | Release |
|---|---|---|
| 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 |