In-Progress Emergency Private Call

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.

Key Features

• Designates an active, established point-to-point emergency call session within MCPTT.
• Triggers network-enforced priority and pre-emption mechanisms (eMPS, QoS).
• Enables specific authorized controls (e.g., authorized termination) for the call.
• Requires distinct session state management in both client and server.
• Often associated with location reporting and other emergency-related supplementary services.
• Operates within the standardized MCPTT service architecture for interoperability.

Evolution Across Releases

Defining Specifications