Call Related

Description

In 3GPP specifications, 'Call Related' is a term used in the context of Location Services (LCS) to describe any LCS-related operation that is associated with an established call in the Circuit Switched (CS) domain or a session via an active Packet Data Protocol (PDP) context in the Packet Switched (PS) domain. This classification is important for distinguishing between location requests that are triggered by or during an ongoing call (e.g., emergency calls, location-based services during a voice call) and those that are standalone (e.g., periodic location updates).

The term is defined in 3GPP TS 23.271 (Functional stage 2 description of Location Services) and TS 23.273 (5G System Location Services). In the CS domain, a call-related LCS operation is one that occurs while a circuit-switched call is active. For example, when a user dials an emergency number, the network may initiate a location request to determine the caller's position for emergency dispatch. This location request is 'call related' because it is tied to the emergency call. Similarly, in the PS domain, a call-related LCS operation is associated with an active PDP context, such as during a VoIP call or a data session where location information is needed.

The distinction between call-related and non-call-related LCS operations is significant for network resource management, charging, and privacy. Call-related location requests often have higher priority and may be subject to different privacy rules. For instance, emergency call-related location requests are typically exempt from user consent requirements, as they are mandated by regulatory authorities. In contrast, non-call-related location requests, such as those for commercial location-based services, require user consent and may be subject to charging.

Architecturally, the LCS system in 3GPP includes several entities: the Gateway Mobile Location Center (GMLC), the Home Subscriber Server (HSS), the Mobile Switching Center (MSC), the Serving GPRS Support Node (SGSN), the Mobile Station (MS), and the Location Measurement Unit (LMU). For call-related LCS, the MSC or SGSN receives a location request from the GMLC and coordinates with the radio access network to obtain the location estimate. The location information is then returned to the requesting entity. In 5G, the LCS architecture is adapted to the Service-Based Architecture (SBA), with the Location Management Function (LMF) and the Gateway Mobile Location Center (GMLC) interacting via service-based interfaces.

The term 'Call Related' has been maintained in 3GPP specifications from R99 through Rel-19, with only minor formatting changes. The definition has remained technically consistent, reflecting the stability of the concept. The note in the R99 definition, 'A possible separate class for active PDP context is for further study,' was removed in later releases, indicating that the classification of active PDP context sessions as call-related was eventually accepted without the need for a separate class.

In summary, 'Call Related' is a classification for LCS operations that are tied to an ongoing call or session. It ensures that location services are provided appropriately during communication, with the necessary priority and privacy considerations. This term is essential for understanding how location services are integrated with voice and data services in 3GPP networks.

Purpose & Motivation

The term 'Call Related' was introduced to provide a clear classification for Location Services (LCS) operations that are associated with an ongoing call or session. This distinction is necessary because location requests that occur during a call often have different requirements and constraints compared to standalone location requests. For example, during an emergency call, the location must be provided quickly and accurately, and privacy restrictions may be waived. In contrast, a commercial location-based service requested outside of a call may require user consent and may be less time-critical.

By defining 'Call Related' LCS operations, 3GPP enables network operators and service providers to implement appropriate policies for location privacy, priority, and charging. It also facilitates the integration of location services with call control, ensuring that location information is available when needed during a call. This is particularly important for emergency services, where accurate location is critical for dispatching help.

Historically, the concept of call-related location services emerged with the introduction of E-911 (enhanced 911) regulations in the United States and similar mandates worldwide. These regulations required that emergency calls be accompanied by location information. The 3GPP LCS specifications were developed to meet these requirements, and the 'Call Related' classification was created to distinguish emergency and other call-associated location requests from other types. Over time, the term has been adapted to new technologies, including 5G, but its fundamental purpose remains the same: to ensure that location services are properly integrated with communication services.