Remote Party

Description

The Remote Party is a concept defined in 3GPP specifications for the Follow Me (FM) supplementary service, primarily documented in TS 22.087, TS 22.094, TS 23.094, and TS 24.087. It represents a specific E.164 number within a Public Land Mobile Network (PLMN) operator's numbering plan. Unlike a traditional MSISDN, the Remote Party number is not permanently assigned to a subscriber; instead, it serves as a logical address that the Follow Me service can dynamically map to the initiating subscriber's current location or device. This allows the subscriber to receive calls destined for the Remote Party number on any device they are currently using, effectively decoupling the called number from the physical subscription.

The Follow Me service enables the initiating subscriber to modify the Follow Me data associated with the Remote Party number. This data includes forwarding rules, such as the current device's identity or routing information. When a call is placed to the Remote Party number, the network consults the Follow Me data to determine where to route the call. In general, the Remote Party number is not assigned to any subscriber, meaning it is a virtual number. However, in particular cases, the Remote Party can be a subscriber of the PLMN, and the number denotes her basic MSISDN. In such scenarios, the Follow Me service can be used to redirect calls from the subscriber's primary MSISDN to another device or number.

Architecturally, the Remote Party is managed within the core network, specifically by the Home Location Register (HLR) or Home Subscriber Server (HSS) in conjunction with the Follow Me application server. The service logic resides in the network, allowing the subscriber to control the mapping via Unstructured Supplementary Service Data (USSD) or other supplementary service procedures. The E.164 number format ensures global uniqueness and interoperability with the Public Switched Telephone Network (PSTN) and other PLMNs. The Remote Party concept is essential for services like call forwarding, personal number, and unified messaging, where a single number can reach a user across multiple devices.

The Remote Party definition has remained stable across 3GPP releases from Rel-4 through Rel-19, indicating the maturity and continued relevance of the Follow Me service. The specifications 22.087 and 22.094 define the service aspects, while 23.094 and 24.087 specify the network architecture and signaling procedures. The term is closely related to the Follow Me service, MSISDN, and supplementary services. Understanding the Remote Party is crucial for engineers implementing call forwarding and personalization features in mobile networks.

Purpose & Motivation

The Remote Party concept was introduced to support the Follow Me supplementary service, which allows a subscriber to be reached on any device by using a single, logical number. Traditional mobile networks assign a unique MSISDN to each subscription, and calls to that MSISDN are routed to the subscriber's home network and then to the serving MSC. This model does not easily support scenarios where a user wants to receive calls on different devices (e.g., office phone, home phone, mobile) without giving out multiple numbers or manually configuring forwarding on each device. The Follow Me service solves this by introducing a virtual number—the Remote Party—that can be dynamically mapped to the subscriber's current device.

The Remote Party addresses the limitation of static MSISDN assignment by decoupling the called number from the physical subscription. It enables the network to consult a database of Follow Me data to determine the actual destination for a call. This is particularly useful for professionals who move between locations and want a single contact number, or for users who want to consolidate multiple numbers into one. The E.164 format ensures that the Remote Party number is globally unique and can be dialed from any network, including PSTN.

Historically, the Follow Me service was defined in early 3GPP releases (Rel-4) as part of the supplementary services framework. The Remote Party term was introduced to provide a clear reference to the logical number used in the service. Over time, the definition has not changed, reflecting the stability of the service and its underlying principles. The Remote Party remains a key concept for operators offering advanced call routing and personalization services, and it is a precursor to modern unified communications and number portability solutions.