User Services Profile

Description

The User Services Profile (USP) is a logical component of the subscriber data maintained in the Home Subscriber Server (HSS) and, in earlier architectures, the Home Location Register (HLR). It defines the set of telecommunication services that a given subscriber is authorised to use, the current status of each of those services (for example, active, barred, or suspended), and references to the subscriber's service preferences. The USP is not a single flat record; it is a structured collection that can include circuit-switched services, packet-switched services, supplementary services, and, in later releases, IP-based multimedia and data services.

Architecturally, the USP is stored as part of the subscription data that the HSS exposes to other core network elements. When a subscriber attaches or registers, the Mobility Management Entity (MME), Serving GPRS Support Node (SGSN), or Mobile Switching Centre (MSC) retrieves the relevant subscription information from the HSS. The USP portion tells these nodes which services the subscriber may invoke and under what conditions. For example, if a subscriber has not subscribed to a particular supplementary service, the serving node will not allow the corresponding service request. The USP therefore acts as a gatekeeper for service authorisation.

The profile also contains references to service preferences, which allow the network to tailor service behaviour to the subscriber's choices. These preferences can include settings such as preferred language for announcements, call forwarding numbers, or quality-of-service parameters. Because the USP is stored centrally in the HSS, it is consistent across different access networks and serving nodes, enabling a uniform service experience regardless of where the subscriber is located.

In the context of the IP Multimedia Subsystem (IMS), the USP is often extended by the IMS Service Profile, which is a separate but related concept defined in 3GPP specifications such as TS 29.198. The IMS Service Profile contains initial filter criteria that determine which application servers are invoked for a given service request. The USP and the IMS Service Profile together provide a comprehensive view of the subscriber's service entitlements and preferences.

The USP is managed through provisioning interfaces. Operations support systems (OSS) and business support systems (BSS) can create, modify, or delete the USP entries via the HSS's provisioning interfaces, such as the Sh interface or the newer Service Capability Exposure Function (SCEF) APIs. This allows operators to offer self-service portals where subscribers can manage their own service preferences, which are then reflected in the USP.

From a standards perspective, the term is defined in 3GPP TS 21.905 (Vocabulary for 3GPP Specifications) and referenced in TS 22.127 (Service Requirement for the Open Service Access) and TS 29.198 (Open Service Access Application Programming Interface). The definition has remained remarkably stable across releases, indicating that the fundamental concept of a subscriber service profile has not changed even as the underlying network technologies have evolved from circuit-switched to all-IP.

Purpose & Motivation

The User Services Profile exists to provide a single, authoritative source of truth for what services a subscriber is allowed to use and how those services should behave. Before the USP was formalised, service authorisation was often scattered across different network elements, leading to inconsistencies and operational complexity. A subscriber might be able to use a service in one part of the network but not another, or preferences set in one node would not be honoured elsewhere. The USP solves this by centralising service entitlement and preference data in the HSS/HLR, ensuring that any serving node can retrieve the same information.

Another motivation was the need to support a growing number of services beyond basic voice telephony. As networks evolved to support data, multimedia, and supplementary services, the subscription data model had to expand. The USP provides a flexible structure that can accommodate new services without requiring changes to the core network protocols. This extensibility has allowed the same basic concept to serve circuit-switched, packet-switched, and IMS-based services.

Furthermore, the USP enables personalised service delivery. By storing references to service preferences, the network can adapt its behaviour to individual subscribers, improving user experience and enabling differentiated service offerings. This is essential for operators who want to offer tiered services and value-added features.