Location Acquisition Requesting Function

Description

The Location Acquisition Requesting Function (LARF) is a functional entity introduced in 3GPP Release 19 as part of the lawful interception (LI) architecture. It is specified in 3GPP TS 33.127 (Lawful Interception (LI) architecture and function) and TS 33.128 (Protocol and procedures for Lawful Interception). LARF acts as the interface between the Law Enforcement Agency (LEA) and the network's location services, allowing authorized interception of location information for a target subscriber. It is a key component in fulfilling regulatory requirements that mandate location tracking capabilities for law enforcement in 5G and beyond networks.

Architecturally, LARF resides within the Lawful Interception domain and interacts with the Location Management Function (LMF) or equivalent location services in the core network. When an LEA requests location information for a target, the request is mediated by the Lawful Interception Control Function (LICF) or directly by LARF, depending on deployment. LARF then triggers location acquisition procedures, which may involve the LMF, Access and Mobility Management Function (AMF), or other network functions capable of providing location estimates. The acquired location data is then delivered to the LEA via the Handover Interface (HI) in a standardized format, ensuring confidentiality and integrity.

The operation of LARF involves several key procedures. First, the LEA provides a lawful authorization that includes the target identity and the type of location information required (e.g., immediate, periodic, or event-triggered). LARF validates this authorization and initiates the location acquisition process. It may interact with the LMF to obtain the location using control-plane or user-plane positioning methods, such as observed time difference of arrival (OTDOA), assisted GNSS, or NR positioning. The location results are then formatted into LI reports and sent to the LEA's mediation function. LARF also manages the lifecycle of location requests, including cancellation and modification.

LARF is designed to be flexible and scalable, supporting various deployment scenarios including roaming and non-roaming cases. It ensures that location acquisition is performed in a secure and privacy-preserving manner, adhering to the strict requirements of lawful interception. The function also supports the interception of location information for multiple targets simultaneously and can handle high-volume requests. Security mechanisms such as authentication, authorization, and encryption are applied to protect the location data and the interfaces involved.

In summary, LARF is a specialized function that bridges the gap between lawful interception systems and location services in 5G networks. It enables law enforcement to obtain location information efficiently and securely, while ensuring compliance with regulatory and privacy standards. Its introduction in Rel-19 reflects the growing importance of location-based services and the need for robust LI capabilities in modern mobile networks.

Purpose & Motivation

LARF was created to address the need for a standardized, efficient, and secure method for law enforcement agencies to acquire location information of target subscribers in 5G networks. Prior to Rel-19, location acquisition for LI purposes was often handled through proprietary or less integrated mechanisms, leading to interoperability issues and delays. The increasing accuracy and availability of location data in 5G, combined with regulatory mandates, necessitated a dedicated function that could interface with advanced location services like the LMF.

The function solves the problem of fragmented location acquisition by providing a single point of request and control within the LI architecture. It abstracts the complexity of interacting with various location determination technologies and network functions, presenting a unified interface to the LEA. This simplifies the implementation for both network operators and law enforcement, ensuring that location requests are handled consistently and reliably.

Furthermore, LARF enhances privacy and security by enforcing strict authorization and auditing procedures. It ensures that location data is only acquired when legally authorized and that the data is protected during transmission. The introduction of LARF in Rel-19 aligns with the broader 3GPP vision of integrating LI capabilities seamlessly into the 5G service-based architecture, supporting new use cases and regulatory requirements.