Internet Protocol Service Subscriber

Description

An IP service subscriber is a fundamental concept in 3GPP specifications that identifies the end-user or entity subscribing to an IP service provider and utilizing IP-based services. This term appears primarily in 3GPP TS 22.258, which addresses IP service requirements, and TS 22.978, which covers IP multimedia services. The concept is essential for defining service-level agreements, charging, and quality of service parameters in mobile networks.

In the 3GPP architecture, the IP service subscriber represents the consumer of IP services, which can include web browsing, VoIP, video streaming, and other packet-switched applications. The subscriber is associated with a subscription profile that defines the services they are authorized to use, their QoS entitlements, and charging rules. This profile is stored in network entities such as the HSS (Home Subscriber Server) or UDR (Unified Data Repository) and is used by policy and charging functions like the PCRF (Policy and Charging Rules Function) or PCF (Policy Control Function) to enforce service policies.

The IP service subscriber concept is distinct from the network subscriber (e.g., a UE with a SIM card) because it focuses on the service layer rather than the access layer. A single network subscriber may have multiple IP service subscriptions, and conversely, an IP service subscriber may access services through different access networks. This abstraction allows service providers to manage subscriptions independently of the underlying radio access technology.

From a charging perspective, the IP service subscriber is the entity to whom charges are billed. The 3GPP charging architecture, defined in TS 32.240 and related specifications, uses the subscriber identity to correlate charging records across different network domains. Online and offline charging systems rely on this identity to apply the correct tariffs and to generate billing records.

In the context of IP Multimedia Subsystem (IMS), the IP service subscriber is often equated with the IMS subscriber, who is identified by an IMPI (IP Multimedia Private Identity) and one or more IMPUs (IP Multimedia Public Identities). The IMS service profile, stored in the HSS, defines the services that the subscriber can access, such as voice, video, and messaging.

Overall, the IP service subscriber is a key entity that bridges the gap between network-level connectivity and service-level delivery, enabling operators to offer differentiated services and to monetize their networks effectively.

Purpose & Motivation

The term 'IP service subscriber' was introduced to provide a clear distinction between the entity that subscribes to IP services and the underlying network subscription. In early mobile networks, services were tightly coupled with the access technology, making it difficult to offer IP-based services across different access types. The introduction of this term in 3GPP Release 7 coincided with the evolution towards all-IP networks, such as LTE and IMS, where service delivery needed to be decoupled from access.

The primary motivation was to enable service providers to manage subscriptions independently of the network operator, and to allow users to access IP services seamlessly across various access networks (e.g., 3GPP, WLAN, fixed broadband). This abstraction also facilitates roaming and interworking between different operators, as the service subscription can be identified and authenticated regardless of the access network.

Furthermore, the term supports the development of advanced charging and policy control mechanisms. By identifying the IP service subscriber, networks can apply personalized QoS, enforce fair usage policies, and generate accurate billing records. This is particularly important for services like VoIP and video streaming, which require specific QoS treatment and may be subject to different charging models.