Subscriber category

Description

Subscriber category is a concept introduced in 3GPP Release 7 within the Policy and Charging Control (PCC) architecture, specified in 23.203 and 23.503. It provides a mechanism to classify subscribers into different groups, often referred to as gold, silver, and bronze users, to enable differentiated Quality of Service (QoS) and charging treatment. This classification is used by the Policy and Charging Rules Function (PCRF) to apply appropriate policies based on the subscriber's category, ensuring that high-priority users receive better service and resource allocation.

In the PCC architecture, the PCRF makes policy decisions based on various inputs, including subscriber category, which is typically stored in the Subscription Profile Repository (SPR) or User Data Repository (UDR). When a subscriber establishes a session, the PCRF retrieves the subscriber's category and uses it to select the appropriate QoS parameters, such as QCI (QoS Class Identifier), ARP (Allocation and Retention Priority), and bit rates. For example, a gold user might be assigned a higher priority and guaranteed bit rate, while a bronze user might receive best-effort service. This allows operators to offer tiered services and monetize network resources effectively.

The subscriber category is also used in charging rules, enabling different charging rates based on the category. This supports business models where premium subscribers pay more for enhanced services. The category can be based on various criteria, such as subscription type, loyalty, or service level agreement. The specifications do not mandate specific categories; they only provide examples (gold, silver, bronze), leaving the definition to operators.

Technically, the subscriber category is conveyed from the SPR/UDR to the PCRF via the Sp/Ud interface. The PCRF then generates PCC rules that include the QoS parameters and charging instructions, which are sent to the PCEF (Policy and Charging Enforcement Function) in the gateway (e.g., PGW). The PCEF enforces these rules, ensuring that the subscriber receives the appropriate treatment. The category may also influence admission control and resource reservation in the access network.

The concept has evolved with the introduction of 5G, where the Policy Control Function (PCF) in the 5G Core (5GC) performs similar functions. The subscriber category remains a key input for policy decisions, enabling network slicing and differentiated services. In Release 20, the wording was slightly revised to remove the definite article before the examples, but the meaning remains the same. Overall, subscriber category is a fundamental tool for QoS differentiation and service tiering in mobile networks.

Purpose & Motivation

Subscriber category was introduced to address the need for differentiated treatment of subscribers based on their service level agreements or subscription profiles. In early mobile networks, all subscribers were treated equally, which limited operators' ability to offer tiered services and optimize network resources. As networks evolved to support multiple services with varying QoS requirements, the need for a mechanism to prioritize certain subscribers became evident. The subscriber category provides this by grouping subscribers into classes, enabling the network to allocate resources and apply policies accordingly.

The motivation for this concept comes from the desire to monetize network investments by offering premium services. For example, an operator could offer a gold category with guaranteed bit rates and low latency, a silver category with moderate guarantees, and a bronze category with best-effort service. This allows operators to segment the market and generate additional revenue. Additionally, during network congestion, the category can be used to ensure that high-priority subscribers (e.g., emergency services or enterprise users) receive preferential treatment.

Historically, the introduction of the PCC architecture in Release 7 provided the framework for policy control, and subscriber category became a key parameter for policy decisions. It solved the problem of uniform treatment by enabling fine-grained control over QoS and charging. With the advent of 5G, the concept has been extended to support network slicing and diverse use cases, where subscriber category helps in selecting the appropriate slice and QoS profile. Thus, subscriber category remains a vital tool for operators to manage their networks and deliver differentiated services.