Description
In-Progress Emergency Private Call (IPEPC) is a specific functional state and service within the 3GPP-defined Mission Critical Services (MCS) architecture, particularly for Mission Critical Push To Talk (MCPTT). It refers to an ongoing, point-to-point emergency private call between two MCPTT users. The 'In-Progress' designation is crucial for network and client logic, indicating that the emergency session has been successfully established and is active, differentiating it from a requested or pending emergency call. The architecture involves the MCPTT client on the User Equipment (UE), the MCPTT application server, and the underlying 3GPP core network (EPC or 5GC). The MCPTT server is responsible for recognizing the emergency nature of the call, applying specific authorization policies, and managing the session's lifecycle. Key components include the MCPTT service authorization function, the session management protocols, and the QoS mechanisms that prioritize this traffic over the radio and core network. Its role is to provide a guaranteed, managed, and prioritized communication channel for emergency situations between two specific individuals, such as a first responder and a dispatcher, ensuring low latency and high reliability even in congested network conditions. The handling of an IPEPC involves specific procedures for pre-emption, priority treatment, and potential location reporting that are distinct from regular private calls. The state is maintained in both the client and server to coordinate actions like emergency session termination, which may require specific authorized commands.
Purpose & Motivation
IPEPC was created to fulfill the stringent requirements of public safety and mission-critical communications over 3GPP networks. Traditional commercial voice services lacked the granular control, priority, and management features needed for life-critical scenarios. The concept addresses the problem of managing an active emergency call session, ensuring it cannot be inadvertently dropped or deprioritized by other network traffic. It provides a standardized mechanism for the network to identify, protect, and control these specific calls. Historically, professional mobile radio (PMR) systems like TETRA had proprietary mechanisms for emergency calls, but the move to broadband LTE and 5G required 3GPP to standardize these capabilities to ensure interoperability between vendors and across borders. IPEPC, as part of the broader MCPTT suite in 3GPP Release 13 and beyond, solves the limitation of previous cellular systems which treated all voice calls with relatively equal priority, making them unsuitable for first responder communications where an active emergency channel must be preserved above all else.
Classification
Detected Changes Across Releases
from 3GPP Change RequestsSpecific changes extracted from the „Change history“ tables of 3GPP specifications (234 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 IPEPC (In-Progress Emergency Private Call) function was newly introduced, specifying procedures for the origination and upgrade of an MCVideo emergency private call with optional emergency alert initiation. The release also defined the cancellation of the MCVideo emergency private call priority and introduced support for managing these calls both on-network and off-network. Furthermore, it established that these emergency private calls utilize an adjusted EPS bearer priority, though they do not use dedicated emergency bearers.
- Remotely initiated private call client procedures TS 24.379CR0356
- Remotely initiated private call server procedures TS 24.379CR0357
- 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
- MCVideo Emergency location triggering criteria TS 24.281CR0070
+ 5 more changes
In Release 16, the IPEPC function was enhanced to support the origination of an MCVideo emergency private call with the optional initiation of an accompanying MCVideo emergency alert. Furthermore, the release introduced procedures for upgrading an existing MCVideo private call to an emergency private call and for the subsequent cancellation of the MCVideo emergency private call priority.
- 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
- 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
- Emergency Alerts for MCData – client procedures TS 24.282CR0127
+ 23 more changes
In Release 17, the IPEPC function introduced new procedures for on-network private communication emergency calls within MCData, including support for pre-established sessions and the ability to upgrade or cancel such emergency calls. It also defined specific handling for emergency alert area notifications at the client side for both MCVideo and MCData services. Furthermore, the release added functionalities for call transfer and call forwarding specifically for MCPTT private calls as part of the call control enhancements.
- Call control - Restricting MCVideo private communications TS 24.281CR0105
- Emergency alert area notification functionalities handling for MCVideo TS 24.281CR0106
- Emergency alert area notification handling at client side for MCVideo TS 24.281CR0112
- Interconnect - MCVideo Emergency Alert procedures TS 24.281CR0153
- Interconnect - MCVideo Private call procedures TS 24.281CR0157
- FA as a target user for MCVideo private call TS 24.281CR0177
+ 77 more changes
In Release 18, the enhancements for the In-Progress Emergency Private Call (IPEPC) function specifically introduced the capability to upgrade an existing MCVideo private call to an MCVideo emergency private call, as detailed in the procedures for MCVideo emergency private calls. Furthermore, the release defined the origination of an MCVideo emergency private call with the optional initiation of an accompanying MCVideo emergency alert. It also standardized the procedure for the cancellation of the MCVideo emergency private call priority once the emergency condition ends.
- Emergency alert to MCVideo client affiliating after a group has moved to emergency alert state TS 24.281CR0238
- Support for emergency adhoc group call and imminent peril adhoc group call - MCVideo TS 24.281CR0257
- Emergency alert to MCData client affiliating after a group has moved to emergency alert state TS 24.282CR0381
- 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
+ 73 more changes
In Release 19, the enhancements for the In-Progress Emergency Private Call (IPEPC) function primarily focused on refining the criteria for determining and modifying the list of participants during an ongoing ad hoc group emergency alert. The changes introduced more dynamic control, allowing authorized users to modify participant criteria and release ad hoc group calls. Additionally, the release added procedures for an emergency remote floor request and provided clarifications for private call transfer and forwarding within the MCPTT service.
- Adhoc group emergency alert add criteria to the SIP message containing the participant lists sent to the authorised users TS 24.281CR0279
- Modifying the criteria for determining the participants during an ongoing ad hoc group emergency alert TS 24.281CR0282
- Adhoc group emergency alert add criteria to the SIP message containing the participant lists sent to the authorised users TS 24.282CR0450
- Modifying the criteria for determining the participants during an ongoing ad hoc group emergency alert TS 24.282CR0456
- 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
+ 26 more changes
Explore further
Broader topics and technologies where IPEPC plays a role.
Defining Specifications
3GPP specifications that define or reference IPEPC, 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 |