Subscriber activities

Description

In 3GPP specifications, particularly TS 22.032 and TS 23.035, "subscriber activities" is a term used to describe the various actions or events associated with a subscriber's use of telecommunication services that can be subject to termination. These activities include call-related events such as call set-up and call termination, as well as the invocation of both call-related and call-independent supplementary services. Examples of supplementary services include Call Hold, Call Waiting, Call Transfer, Call Forwarding, and Unstructured Supplementary Service Data (USSD). The term is often used in the context of services that allow the network or the subscriber to terminate these activities, such as the Immediate Service Termination (IST) service.

The IST service, defined in TS 22.032, enables a service provider to terminate all or some subscriber activities immediately. This is useful for scenarios such as fraud detection, where the operator needs to stop a subscriber's ongoing calls or supplementary service invocations to prevent further unauthorized charges. The IST service can be invoked by the network, and it must be able to terminate any of the listed subscriber activities. The specification TS 23.035 provides the Stage 2 details for IST, describing how the network entities interact to achieve termination.

Subscriber activities are categorized into call-related events and supplementary service invocations. Call-related events include the establishment (set-up) and release (termination) of calls. Supplementary services can be call-related (e.g., Call Hold, Call Waiting, Call Transfer, Call Forwarding) or call-independent (e.g., USSD). USSD is a protocol used for transmitting short messages between the mobile station and the network, often for service control or information retrieval. All these activities can be subject to termination by the IST service.

The ability to terminate subscriber activities is important for network management and security. For example, if a subscriber's account is suspended due to non-payment or suspected fraud, the network can use IST to immediately terminate any ongoing calls or service invocations. This ensures that the subscriber cannot continue to use services without authorization. The IST service is typically implemented in the core network, with interactions between the Mobile Switching Center (MSC), the Home Location Register (HLR), and possibly the Service Control Point (SCP) in an Intelligent Network (IN) architecture.

In the context of IMS and 5G, similar concepts exist for terminating sessions and services. For instance, the Policy and Charging Rules Function (PCRF) or Policy Control Function (PCF) can enforce policies that result in session termination. However, the term "subscriber activities" is specifically tied to the IST service and its associated specifications. It highlights the need for a comprehensive list of activities that can be terminated, ensuring that the service is effective in stopping all relevant usage.

Overall, subscriber activities represent the set of actions that a subscriber can perform within the network, which may need to be terminated under certain conditions. The term is essential for defining the scope of termination services and ensuring that network operators have the tools to manage subscriber usage effectively.

Purpose & Motivation

The term "subscriber activities" was introduced to define the scope of services that allow the network to terminate a subscriber's ongoing usage. The primary motivation was the need for an Immediate Service Termination (IST) capability, which operators require to combat fraud and enforce service restrictions. Without a clear definition of what constitutes subscriber activities, it would be ambiguous which actions could be terminated, leading to potential gaps in fraud prevention or service control.

Historically, as mobile networks evolved and supplementary services became more prevalent, the potential for misuse increased. Fraudsters could exploit services like Call Forwarding or USSD to incur charges without paying. Operators needed a mechanism to immediately stop such activities. The IST service was defined in 3GPP Release 4 (TS 22.032) to address this need. The term "subscriber activities" was coined to encompass all the actions that could be subject to termination, including call set-up, call termination, and the invocation of various supplementary services.

The definition also serves to clarify the scope for implementers. By listing examples such as Call Hold, Call Waiting, Call Transfer, Call Forwarding, and USSD, the specifications ensure that all relevant activities are considered. This comprehensive approach helps in designing network elements that can handle termination requests for any of these activities. It also facilitates interoperability between different vendors' equipment, as the expected behavior is clearly defined.

In summary, the term "subscriber activities" exists to provide a precise and comprehensive description of the actions that can be terminated by services like IST. It addresses the limitations of previous approaches where termination might have been limited to basic calls only, and it supports the ongoing need for robust service control and fraud management in mobile networks.