Description
The MCPTT Imminent peril Group Call (MIGC) is the instantiated communication session associated with an MCPTT Imminent peril Group (MIG). While the MIG defines the group's membership and emergency status, the MIGC is the active group call that carries the voice media when the group is engaged during an imminent peril situation. It represents the realization of the prioritized communication channel that the MIG concept promises.
Architecturally, a MIGC is established and controlled by the MCPTT application server upon request from an authorized MCPTT user (client). The call setup signaling flows through the MCPTT service layer, which instructs the underlying 3GPP network to establish bearers with specific Quality of Service (QoS) characteristics. Key components include the MCPTT clients of all group members, the MCPTT server (controlling call state and floor control), and the core network elements (PCRF, PGW/UPF, SMF) that enforce the QoS policies. The call is identified as an Imminent peril Group Call, distinguishing it from regular MCPTT group calls.
The operation of a MIGC follows a stringent procedure. When initiated, the MCPTT server recognizes the group's imminent peril status and applies the highest priority level to the call setup and media transmission. This typically involves using a pre-emptive Priority Level in floor control requests, ensuring the requesting user immediately gains the right to speak. Concurrently, the network establishes dedicated EPS bearers or QoS Flows with a high-priority QoS Class Identifier (QCI) and an Allocation and Retention Priority (ARP) value that may pre-empt other bearers. Media packets for the MIGC are marked accordingly and receive prioritized treatment throughout the radio access network (RAN) and core network. The MIGC remains active until explicitly ended, providing a continuous, protected channel for crisis coordination. Its role is to be the definitive, high-integrity voice pipeline for personnel in danger.
Purpose & Motivation
The MIGC exists to operationalize the Imminent peril Group concept, translating a configured group definition into a live, prioritized communication session. Simply having a designated group is insufficient; the system must guarantee that when a call is made within that group under perilous conditions, it receives deterministic, high-priority treatment from end to end. The MIGC specification ensures this by defining the precise call type and its associated network behaviors.
It solves the problem of ensuring that the act of calling during an emergency receives the necessary network resources without delay. Previous systems might have prioritized the group in theory, but the call setup itself could be delayed by congestion. The MIGC mandates that the call establishment signaling and the subsequent media plane are both prioritized. This end-to-end prioritization is critical for reducing latency from the moment the push-to-talk button is pressed to when audio is heard by all group members.
Created alongside the MIG in 3GPP Release 13 as part of MCPTT Phase 1, its motivation was to provide a complete, standardized emergency communication procedure. It addresses the limitations of ad-hoc emergency calls by defining a formalized session type that networks and devices can recognize and handle specially. The MIGC ensures interoperability between different vendors' MCPTT systems and public safety networks, guaranteeing that an imminent peril call from one agency's device receives the same urgent treatment on another agency's network, which is vital for cross-border or mutual-aid incidents.
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 Call (MIGC) function was introduced, establishing procedures for both the client and server to handle remotely initiated group calls. This included defining the specific "in-progress imminent peril group state" and clarifying the usage of SIP REFER for initiating such group calls. The release also provided corrections to related procedures, such as the TPF procedures for imminent peril calls, to ensure proper session control.
- 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, the MIGC function was enhanced to allow an imminent peril group call to proceed even when the maximum number of simultaneous sessions for a user is already reached. Furthermore, the release introduced subsequent corrections to the procedures for upgrading calls to an emergency or imminent peril state, refining the overall call control mechanisms for these critical scenarios.
- 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 Call (MIGC) function was enhanced through the introduction of comprehensive interconnect procedures, enabling such critical calls between different MCPTT systems. These new procedures, detailed for pre-arranged groups, emergency alerts, and group regrouping, operate through a defined MCPTT Gateway Server functional entity. This allows for the establishment and control of imminent peril group calls across system boundaries, supporting both trusted and untrusted mutual aid relationships.
- 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 MCPTT Imminent Peril Group Call function was enhanced with new support for emergency and imminent peril adhoc group calls, as detailed in the specific protocol implementation. This release also introduced procedures for an "in-progress imminent peril group state," defining the MCPTT client's internal perspective of this critical call type. Furthermore, general adhoc group call procedures were expanded to operate both within a single system and across multiple systems.
- 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, the MCPTT Imminent Peril Group Call (MIGC) function was enhanced with more dynamic criteria for determining participants during an ongoing ad hoc group call or emergency alert. The release introduced the ability for an authorized user to release an ad hoc group call and added clarifications and corrections to procedures for ad hoc group emergency alert cancellation and group regrouping. Furthermore, it provided an option to apply automatic commencement for ad hoc group calls and improved the handling of participant lists in SIP messages sent to authorized users.
- 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 MIGC plays a role.
Defining Specifications
3GPP specifications that define or reference MIGC, 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 |