Initiating Subscriber

Description

The term 'Initiating Subscriber' is defined in 3GPP specifications 22.094 and 23.094, which cover Follow Me services. Follow Me is a supplementary service that allows a subscriber to redirect incoming calls to another number or device, often dynamically. The initiating subscriber is the mobile subscriber who actively modifies the Follow Me data of a remote party. In other words, this is the user who initiates changes to the call forwarding settings of another user (the remote party). This concept is part of the Follow Me service, which enables a user to manage the forwarding of calls for another line, typically with proper authorization.

The Follow Me service is designed for scenarios where a user wants to control the forwarding of calls to their own or another's number. For example, a secretary might manage the call forwarding settings for an executive. The initiating subscriber would be the secretary, who modifies the Follow Me data of the executive (the remote party). The service requires that the initiating subscriber has the necessary permissions to modify the remote party's data. The 3GPP specifications define the procedures and signaling for this service, including how the initiating subscriber requests modifications and how the network validates and applies them.

In terms of architecture, the Follow Me service is implemented in the core network, involving entities such as the Home Location Register (HLR) or Home Subscriber Server (HSS) for storing subscriber data, and the Mobile Switching Center (MSC) or Application Server for executing the service logic. The initiating subscriber's request is typically sent via Unstructured Supplementary Service Data (USSD) or a similar mechanism. The network then checks the authorization of the initiating subscriber and updates the Follow Me data for the remote party. This may involve updating the HLR/HSS and notifying the relevant nodes.

The initiating subscriber concept is specific to the Follow Me service and is not widely used in other contexts. It highlights the distinction between the user who controls the service and the user whose service is being controlled. This separation is important for security and billing purposes. The initiating subscriber may be billed for the service, and the remote party's privacy must be protected. The 3GPP specifications ensure that only authorized initiating subscribers can modify Follow Me data.

Over the releases, the definition of initiating subscriber has remained unchanged from Rel-4 to Rel-19, indicating a stable concept. However, the underlying network architecture has evolved from circuit-switched to all-IP, and the Follow Me service may now be implemented in IMS or via web interfaces. Despite these changes, the fundamental role of the initiating subscriber remains the same. This term is a good example of how 3GPP preserves legacy terminology even as technology advances.

Purpose & Motivation

The Initiating Subscriber concept exists to support the Follow Me supplementary service, which allows a user to remotely manage call forwarding for another line. This is particularly useful in business environments where an assistant manages calls for a manager, or in family settings where one person controls the forwarding for another. Without a clear definition of who initiates the modification, the service would be ambiguous and potentially insecure. The term distinguishes the actor (initiating subscriber) from the target (remote party), ensuring that authorization and billing are correctly applied.

Before the standardization of Follow Me, similar services were proprietary and limited to specific vendors. The 3GPP definition brought interoperability, allowing subscribers to use the service across different networks and vendors. It also provided a framework for security, ensuring that only authorized users can modify Follow Me data. This is crucial because unauthorized modification could lead to calls being forwarded to unintended numbers, potentially causing privacy breaches or toll fraud.

The Initiating Subscriber term also helps in charging and accounting. The network can bill the initiating subscriber for the service usage, while the remote party may not incur charges. This separation is important for commercial deployments. As networks evolve towards 5G and beyond, the Follow Me service may be implemented using new technologies like APIs and cloud-based application servers, but the role of the initiating subscriber remains relevant. The term is a testament to the enduring nature of certain service concepts in telecommunications.