Service User

Description

A Service User, in the context of 3GPP specifications, refers to an individual who is authorized to use the Multi-Level Precedence and Pre-emption (MPS) service and who has been granted a user priority level assignment by a regional or national authority. This definition is primarily used in the context of the MPS service, which is a priority service for government and emergency responders. The Service User must also have a subscription to a mobile network operator that supports the MPS feature. The term is defined in 3GPP TS 22.153 (MPS) and related specifications such as TS 22.950 (Priority Service Guide) and TS 23.228 (IMS).

The MPS service is designed to provide priority access to network resources for authorized users, such as emergency services, government officials, and critical infrastructure personnel. The Service User is the end-user who benefits from this priority treatment. The priority level assignment is typically issued by a regional or national authority, which is an agency authorized to issue such assignments. This ensures that only legitimate users receive priority access and that the priority levels are managed according to national policies. The Service User's subscription with the mobile network operator includes the MPS feature, which enables the network to recognize and enforce the priority level.

In terms of architecture, the MPS service involves several network elements. The Service User's subscription data, including the assigned priority level, is stored in the Home Subscriber Server (HSS) or Home Location Register (HLR). When the Service User initiates or receives a call, the network checks the subscription and the priority level. The MPS service can be applied to various types of communications, including voice calls, video calls, and data sessions. The network enforces priority through mechanisms such as priority admission control, resource reservation, and pre-emption of lower-priority traffic. The Service User may also have access to special features like priority roaming and priority access in visited networks.

The MPS service is defined in 3GPP TS 22.153, which specifies the requirements for MPS in the context of the IP Multimedia Subsystem (IMS) and other network domains. The service is intended to be used by organizations such as Public Protection and Disaster Relief (PPDR) agencies. The Service User concept is closely related to the Service subscriber in eMLPP, but MPS is a more modern, packet-switched oriented service that leverages IMS and LTE/5G capabilities. The Service User is thus a user who has been explicitly authorized by an authority and has a subscription that supports MPS.

The definition of Service User has evolved over time. In early releases (Rel-2 to Rel-7), the term was defined simply as 'A user subscribed to Priority Service.' This was a broad definition that did not specify the authorization aspect. In Rel-8, the definition was changed to include the requirement of a priority level assignment from a regional/national authority and a subscription to a mobile network operator supporting MPS. This change reflected the maturation of the MPS service and the need to clearly identify authorized users. In Rel-14, the definition was further refined to explicitly state that the individual is 'authorized to use MPS' and to clarify that the priority level assignment is granted by an authority. This wording change emphasized the authorization aspect and aligned with the MPS service requirements.

The Service User is a critical concept for ensuring that priority services are used appropriately. It provides a clear identity for users who are entitled to priority treatment, enabling network operators to enforce policies and prevent misuse. The term is used in specifications related to MPS, such as TS 22.153, which defines the service requirements, and TS 23.228, which specifies the IMS architecture that supports MPS. As networks evolve to 5G, the Service User concept continues to be relevant, with MPS being integrated into the 5G priority and QoS framework.

Purpose & Motivation

The Service User concept exists to clearly identify individuals who are authorized to use priority services, specifically the Multi-Level Precedence and Pre-emption (MPS) service. The purpose is to ensure that during emergencies or network congestion, authorized personnel (such as emergency responders) can communicate reliably. Before the introduction of MPS, priority services like eMLPP were available, but they lacked a clear linkage to national authority assignments. The Service User definition addresses this by requiring that the user has received a priority level assignment from a recognized authority, thereby preventing unauthorized use of priority resources.

The MPS service itself was motivated by the need for a standardized, IP-based priority service that could work across different access technologies (e.g., LTE, 5G) and support multimedia communications. The Service User is the beneficiary of this service, and the definition ensures that the priority level is tied to an official assignment. This is important for legal and regulatory reasons, as priority access may be subject to national laws and policies. The Service User concept also facilitates roaming, as visited networks can trust the priority level assigned by the home network based on the authority's assignment.

Over time, the definition of Service User has been refined to better reflect the authorization and subscription aspects. The change from a simple 'user subscribed to Priority Service' to a more detailed definition in Rel-8 and Rel-14 shows the evolution of the MPS service from a generic priority service to a well-defined, authority-driven service. This evolution ensures that the Service User is clearly distinguishable from ordinary users and that the priority mechanisms are applied correctly. The Service User concept is thus a key enabler for mission-critical communications in modern mobile networks.