Description
The In-Progress Imminent Peril Group (IPIG) is a specialized service state within the 3GPP Mission Critical Services (MCS) framework, specifically for Mission Critical Push To Talk (MCPTT) group calls. It denotes a group call that has been successfully established and is currently active, where the initial call setup was triggered by an 'imminent peril' emergency declaration from a user. Imminent peril indicates a situation involving immediate threat to life or health. The architecture involves the MCPTT client, the MCPTT application server, and the group management system. The MCPTT server plays a central role in creating and managing the IPIG session. It identifies the call as an imminent peril group call based on the initial request, applies specific emergency group call policies, and dynamically manages the group session. Key components include the group call processor, the imminent peril alerting function, and the integration with priority mechanisms in the underlying 3GPP core (e.g., GCSE_LTE for group communication system enablers). Its role is to facilitate rapid, one-to-many emergency communication for teams facing a critical incident. The 'In-Progress' state is significant for network and client behavior; it influences floor control policies (who can speak), mandatory listening modes for group members, and the application of the highest possible QoS and pre-emption levels across the radio access network (RAN) and core network. The server may also invoke location updates for all participants and maintain a persistent session until an authorized user terminates the imminent peril state.
Purpose & Motivation
The IPIG concept was developed to address the critical need for instant, reliable group communication during emergency situations in public safety and mission-critical operations. Traditional cellular group calls lacked the urgency flagging and resource guarantees required for coordinated responses to immediate threats. IPIG solves the problem of escalating a regular group call into a highest-priority emergency session that commands network resources. It was motivated by the operational procedures of first responder agencies, where alerting an entire team to a life-threatening situation (imminent peril) requires an unmistakable, high-priority communication channel. Prior to 3GPP standardization in Release 13, similar functionalities were vendor-specific or relied on narrowband PMR systems. Standardizing IPIG within MCPTT ensures that different agencies and countries can interoperate during joint operations, and that the network provides deterministic performance for these calls, overcoming the best-effort limitations of earlier commercial group communication services over LTE.
Classification
Detected Changes Across Releases
from 3GPP Change RequestsSpecific changes extracted from the „Change history“ tables of 3GPP specifications (285 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 IPIG (In-Progress Imminent Peril Group) function was introduced, which includes new procedures for managing MCVideo imminent peril group calls and states, as detailed in the call control protocol specifications. This release also introduced corrections to the TPF (Talker Priority and Floor control) procedures specifically for handling imminent peril calls. Furthermore, it established the client's internal perspective and state management for an MCVideo imminent peril group and its associated group calls.
- Subscription to group dynamic data TS 24.281CR0061
- 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
+ 8 more changes
In Release 16, the IPIG function was enhanced to support automatic triggering of an emergency group call following an emergency alert and to allow such emergency and imminent peril calls even when the maximum number of simultaneous sessions is reached. It also introduced procedures for the server to store preconfigured regroup information and to check for groups that are already regrouped before initiating a new regroup operation.
- Initiating group SDS communication using pre-established session TS 24.282CR0086
- Support for MCData emergency alert and communications MCC note: This CR introduces the abbreviation IMPU; MCC has added this in the list of abbreviations, choosing the most appropriate of the five variations appearing in other 3GPP Specs. Similarly, MCC has provided the expansions of abbreviations UUID and URN introduced, but not defined by, this CR. The newly introduced term "Group identity" has a circular definition. In §D.1.3,, "can" has been changed to "may" in newly introduced bullet points 11 c), 11 c) i), and 11 e). TS 24.282CR0126
- 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
+ 19 more changes
In Release 17, the new IPIG function introduced standardized on-network group emergency and imminent peril communications, including specific client and server procedures. This included updates to emergency alert handling and the formal definition of states for imminent peril group calls and group states within the MCVideo service. The release also added procedures for group area configuration and for supporting functional aliases used by affiliated group members.
- Check for Preconfigured Group Use Only TS 24.281CR0104
- Entry into or exit from a group geographic area functionality handling for MCVideo TS 24.281CR0107
- Functional alias association with MCVideo group - protocol implementation TS 24.281CR0141
- Interconnect - MCVideo group call procedures TS 24.281CR0156
- Interconnect - MCVideo Remote change of selected group procedures TS 24.281CR0159
- Group area configuration procedure TS 24.281CR0176
+ 77 more changes
In Release 18, the IPIG function was enhanced with new procedures for emergency and imminent peril ad hoc group calls within MCVideo and MCData services. This included specific support for clients affiliating to a group after it has already moved to an emergency alert state, ensuring they receive the alert. Furthermore, the release introduced procedures to determine users based on criteria for inviting to or releasing from an ad hoc group session.
- 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
- General Adhoc group call procedures using pre-established session in Single system - Protoc impl for MCVideo TS 24.281CR0229
- Subscribe to the participant information of the ongoing ad hoc group call - MCVideo TS 24.281CR0237
- General adhoc group call procedures in multiple systems - Protoc impl for MCVideo TS 24.281CR0235
- General Adhoc group call procedures using pre-established session in Single system - procedures at CF (mcvideo) TS 24.281CR0236
+ 97 more changes
In Release 19, the IPIG function was enhanced with new capabilities for modifying participant criteria dynamically during an ongoing ad hoc group emergency alert across MCPTT, MCVideo, and MCData services. These enhancements also included adding specific criteria to the SIP messages containing participant lists sent to authorized users and introducing procedures for ad hoc group calls to migrated users. Furthermore, the release added support for authorized users to release ad hoc group calls and introduced the option to apply automatic commencement for such calls.
- 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
- Modify list of participants by changing the criteria during an ongoing MCData ad hoc group data communication TS 24.282CR0447
+ 54 more changes
Explore further
Broader topics and technologies where IPIG plays a role.
Defining Specifications
3GPP specifications that define or reference IPIG, 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 24.282 vj50 | MCData Signalling Control Protocols | 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 |