Multimedia Priority Service Session

Description

An MPS session is a communication session that is granted priority treatment in the allocation and maintenance of radio and network resources to support the Multimedia Priority Service (MPS). MPS is a 3GPP-defined service that provides priority access to network resources for authorized users, such as emergency responders, government officials, and other critical personnel, especially during times of network congestion or emergencies. The MPS session is established when a user with MPS subscription initiates a communication, and the network applies priority handling to ensure that the session is established and maintained with higher precedence than normal sessions.

The priority treatment for an MPS session encompasses several aspects of network resource management. In the radio access network, the session may be assigned higher priority in scheduling, admission control, and handover decisions. This ensures that the MPS session receives sufficient radio resources even when the network is heavily loaded. In the core network, the session may be given priority in bearer establishment, QoS allocation, and mobility management. The network may also pre-empt lower-priority sessions to free up resources for the MPS session if necessary. The priority treatment is applied end-to-end, from the user equipment (UE) through the radio access network (RAN) and core network to the external network.

The MPS session is defined in 3GPP specifications such as TS 22.153 (Multimedia priority service), TS 23.228 (IP Multimedia Subsystem (IMS)), TS 23.854 (Enhancements for Multimedia Priority Service), TS 29.214 (Policy and charging control over Rx reference point), and TS 29.514 (5G System; Policy Authorization Service). These specifications outline the requirements, architecture, and procedures for MPS, including how sessions are identified, how priority is requested and authorized, and how the network enforces priority treatment. The MPS session is typically associated with a user who has an MPS subscription, and the network verifies the user's authorization before granting priority.

In practice, an MPS session can be a voice call, video call, or data session that requires priority handling. The session may be established over IMS or other IP-based services. The network uses indicators such as the MPS session indication, which may be included in session establishment requests, to identify the session as requiring priority. The policy and charging control (PCC) framework plays a key role in authorizing and enforcing priority treatment, ensuring that the MPS session receives the appropriate QoS and priority. The MPS session concept has evolved over releases, with enhancements to support new services and network architectures, including 5G.

The importance of MPS sessions lies in their ability to provide reliable and timely communication for critical users when the network is congested or degraded. By ensuring priority access, MPS sessions help maintain essential services during emergencies, natural disasters, or other situations where network resources are scarce. This makes MPS a vital component of public safety and emergency communications.

Purpose & Motivation

The MPS session concept was created to address the need for prioritized communication for critical users, such as emergency responders and government officials, during times when network resources are congested or unavailable. In normal network conditions, all users share resources fairly, but during emergencies or large-scale events, the network can become overloaded, leading to call blocking or degradation for everyone. MPS ensures that authorized users can still communicate when they need it most, by giving their sessions priority over ordinary traffic.

Before MPS, there was no standardized way to provide priority treatment across different networks and services. Emergency services might have had some priority, but it was often limited to specific technologies or not end-to-end. MPS was introduced in 3GPP Release 10 to provide a comprehensive framework for priority treatment across radio, core, and service layers, including IMS-based multimedia services. This allows critical users to make voice and video calls, send data, and access other services with higher priority, even when the network is congested.

The MPS session is the fundamental unit of priority treatment. By defining what constitutes an MPS session and how it is handled, 3GPP enables operators to implement priority services in a consistent and interoperable manner. This is essential for public safety, disaster response, and other mission-critical communications, where reliable and timely information exchange can save lives. The MPS session concept continues to evolve with new releases, adapting to new network architectures like 5G and new service requirements.