End-User

Description

In 3GPP terminology, an End-User is the ultimate consumer of telecommunications services. Unlike a subscriber, which is a legal or commercial entity that contracts with a network operator, an End-User is the actual person or entity that uses the service. The End-User is associated with one or multiple subscriptions, each identified by various identities such as IMSI (International Mobile Subscriber Identity), MSISDN (Mobile Station International Subscriber Directory Number), IMPI (IP Multimedia Private Identity), IMPU (IP Multimedia Public Identity), and application-specific identities. This association allows the network to link the human user to the technical subscription data and service entitlements.

The concept of End-User is fundamental to service delivery and personalization. It enables the network to distinguish between the device, the subscription, and the person using the service. For example, a single End-User may have multiple devices (phone, tablet, IoT device) each with its own subscription, or a single subscription may be shared among multiple End-Users (e.g., family plan). The End-User Identity is used for authentication, authorization, accounting, and service customization. It also plays a crucial role in regulatory requirements such as lawful interception and emergency services, where the actual user behind a subscription must be identifiable.

In the context of IMS (IP Multimedia Subsystem), the End-User is represented by IMPI and IMPU. The IMPI is a private identity used for authentication, while the IMPU is a public identity used for routing and service invocation. An End-User may have multiple IMPUs for different services (e.g., voice, video, messaging). The 3GPP system uses these identities to manage service access, mobility, and session control. The End-User concept also extends to application-layer services, where application-specific identities (e.g., email address, SIP URI) are used to reach the user.

From a management perspective, the End-User is the subject of various subscription management functions. The HSS (Home Subscriber Server) stores subscription data linked to End-User identities, and the PCRF/PCF (Policy and Charging Rules Function) applies policies based on the End-User's subscription. The End-User Identity is also used in charging and billing systems to generate accurate records. In 5G, the concept is further refined with the UDR (Unified Data Repository) storing subscription data and the UDM (Unified Data Management) managing End-User authentication and authorization.

The definition of End-User has remained stable across 3GPP releases from Rel-8 to Rel-19, reflecting its foundational nature. However, the identities associated with End-Users have expanded with new technologies, such as 5G-specific identifiers (SUPI, GPSI) and IoT-specific identities. The End-User remains a central concept for ensuring that services are delivered to the right person with the right permissions and quality of experience.

Purpose & Motivation

The End-User concept exists to bridge the gap between technical subscriptions and the actual humans or entities that use telecommunications services. In early mobile networks, the focus was on the device and the subscription, but as services became more personalized and complex, it became necessary to distinguish the user from the subscription. This distinction enables service providers to offer tailored services, manage multiple devices per user, and enforce regulatory requirements.

Before the formalization of the End-User concept, network operations were primarily subscription-centric. A subscription was tied to a SIM card and a device, and the user was implicitly the person holding the device. However, with the advent of IMS, multi-device scenarios, and application-layer services, this model became insufficient. The End-User concept allows a single user to be associated with multiple subscriptions and identities, and conversely, a single subscription to be shared by multiple users. This flexibility is essential for family plans, corporate accounts, and IoT deployments.

Furthermore, the End-User concept is critical for security and privacy. By clearly defining the End-User and their identities, the network can authenticate the user, authorize access to services, and protect privacy through identity confidentiality. It also supports lawful interception and emergency call handling by ensuring that the user behind a subscription can be identified when legally required. The stability of the definition across releases underscores its fundamental importance to 3GPP systems.