Description
The In-Progress Emergency Group (IPEG) is a service capability defined within the 3GPP framework for Mission Critical Services (MCS), particularly Mission Critical Push To Talk (MCPTT). It is a specialized feature that manages the dynamic membership of an ongoing emergency group communication session. Unlike pre-defined static groups, an IPEG is characterized by its fluid composition, which can be altered in real-time by an authorized user while the group call is active.
Architecturally, IPEG functionality is implemented within the MCPTT application server and client. When an emergency group call is initiated, it may start with a set of initial members (e.g., a pre-configured emergency response team). The user designated with the "Floor Control" authority, often the incident commander, is granted special privileges to manage the IPEG. Through their MCPTT client interface, they can send requests to the MCPTT server to add new participants (e.g., other responders arriving on scene) or remove existing ones. The server then signals the involved parties, updating their group membership status and media distribution paths.
The protocol mechanics are detailed in specifications like 24.379 (MCPTT protocol). The process involves specific control messages for "In-Progress Emergency Group Add Request" and "In-Progress Emergency Group Remove Request." Security is paramount; only authorized users with the correct credentials and currently holding the "floor" in the emergency call can execute these commands. The MCPTT server validates each request, checks authorization policies, and then updates the active session state, ensuring all participants receive the updated roster and media streams.
IPEG operates within the broader ecosystem of Mission Critical Services over LTE/5G (MCX). It relies on underlying IMS core for registration, authentication, and session control, and utilizes evolved group communication system enablers. The feature is crucial for adapting to the unpredictable nature of emergency scenarios, where the set of required communicants evolves rapidly. It ensures that the communication group remains relevant and effective throughout the incident's lifecycle, directly supporting coordinated response efforts.
Purpose & Motivation
IPEG was developed to address a critical shortcoming in traditional group communication systems used by public safety and first responders. In emergency situations, the composition of personnel involved changes dynamically—new units arrive, others are reassigned, or some may become incapacitated. Static, pre-defined talk groups cannot accommodate this fluidity, forcing responders to switch between multiple groups or use inefficient broadcast methods, wasting precious time and increasing confusion.
The creation of IPEG within 3GPP's Mission Critical Services standards was motivated by the need for agile, commander-led communication. It empowers the incident commander to maintain a single, authoritative communication channel that can be instantly tailored to the evolving tactical picture. This solves the problem of information silos and ensures all relevant parties are included in critical directives and situational updates.
Before standardized MCPTT features like IPEG, similar capabilities were proprietary to specific Land Mobile Radio (LMR) vendors, hindering interoperability between different agencies. By standardizing IPEG in 3GPP Release 13 and beyond, it ensures that mission-critical communication tools can work seamlessly across commercial LTE/5G networks, facilitating joint operations between police, fire, medical, and other services regardless of their device or network provider. It represents a shift from technology-limited radio channels to flexible, service-rich digital group communications.
Classification
Detected Changes Across Releases
from 3GPP Change RequestsSpecific changes extracted from the „Change history“ tables of 3GPP specifications (312 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 In-Progress Emergency Group (IPEG) function was newly introduced to manage the dynamic state of an emergency event within a group. This included defining specific client and server states, such as the "MCVideo emergency group state," which represents the client's internal perspective of a group's in-progress emergency status maintained by the controlling function. The release also introduced procedures for subscription to group dynamic data and for the remote initiation of group call client and server procedures to support this function.
- 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
- Enter-Exit emergency alert area TS 24.379CR0411
+ 9 more changes
In Release 16, the IPEG function was enhanced to support triggering an emergency group call automatically after an emergency alert is initiated. This release also introduced support for using functional aliases within emergency alerts and added procedures for listing group members who did not acknowledge the emergency group call request. Furthermore, it defined mechanisms for automatic group affiliation and deaffiliation based on a user's location or functional alias.
- Emergency Alerts for MCData – General sections TS 24.282CR0066
- Emergency Alerts for MCData – sending origination request, on-network TS 24.282CR0067
- Emergency Alerts for MCData – cancelation, on-network TS 24.282CR0068
- Initiating group SDS communication using pre-established session TS 24.282CR0086
- Add off-network emergency alert to MCData TS 24.282CR0095
- 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
+ 30 more changes
In Release 17, the IPEG function was enhanced with new procedures for handling emergency alert area notifications and group geographic area entry/exit for MCVideo, as indicated by the new CR titles. Furthermore, support was added for interconnect procedures for MCVideo Emergency Alerts and group calls, and for MCData procedures limiting emergency group participations per functional alias and supporting on-network private communication emergencies.
- Check for Preconfigured Group Use Only TS 24.281CR0104
- Emergency alert area notification functionalities handling for MCVideo TS 24.281CR0106
- Entry into or exit from a group geographic area functionality handling for MCVideo TS 24.281CR0107
- Emergency alert area notification handling at client side for MCVideo TS 24.281CR0112
- Functional alias association with MCVideo group - protocol implementation TS 24.281CR0141
- Interconnect - MCVideo Emergency Alert procedures TS 24.281CR0153
+ 87 more changes
In Release 18, the IPEG function was enhanced to support **emergency adhoc group calls** and **imminent peril adhoc group calls** for both MCVideo and MCData services. This included new procedures for clients affiliating to a group already in an **emergency alert state** and mechanisms to determine users to invite or release from such adhoc sessions. Furthermore, support was extended for these adhoc group procedures in both single and multiple systems, including using pre-established sessions.
- 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
+ 100 more changes
In Release 19, the In-Progress Emergency Group (IPEG) function was enhanced to allow authorized users to dynamically modify the participant list criteria during an ongoing ad hoc group emergency alert or group call for MCPTT, MCData, and MCVideo services. This release also introduced the ability for an authorized user to release an entire ad hoc group call and added specific criteria to the SIP messages containing participant lists sent to authorized users during an emergency alert. Furthermore, support was extended for handling ad hoc group calls to migrated users across these mission critical services.
- 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
+ 56 more changes
Explore further
Broader topics and technologies where IPEG plays a role.
Defining Specifications
3GPP specifications that define or reference IPEG, 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 |