Network Induced Location Request

Description

Network Induced Location Request (NI-LR) is a core network-driven procedure within the 3GPP Location Services (LCS) architecture. It enables an authorized entity, known as a LCS Client, to request the geographical position of a target UE. The key characteristic of NI-LR is that the location request is triggered by the network or an external application server, not by the UE (which would be a Mobile Originated Location Request, MO-LR). The requesting LCS Client can reside within the network operator's domain (e.g., for emergency services, lawful interception) or be an external, trusted third-party service provider (e.g., for logistics or asset tracking). The request is submitted to the Gateway Mobile Location Centre (GMLC), which acts as the gateway and privacy authorizer for all location requests.

Upon receiving a validated NI-LR, the GMLC routes the request to the appropriate serving node in the core network—the Mobile Switching Centre (MSC) for circuit-switched (CS) access, the Serving GPRS Support Node (SGSN) for 2G/3G packet-switched (PS) access, or the Mobility Management Entity (MME) for 4G/5G access. This serving node then initiates the positioning procedure with the target UE and the radio access network (RAN). The specific positioning method (e.g., Cell-ID, OTDOA, UTDOA, A-GNSS) is determined by the network based on the required Quality of Service (QoS) such as accuracy and response time. The RAN and/or UE perform the necessary measurements (e.g., timing measurements for OTDOA, satellite signals for A-GNSS) and report them to a dedicated network node, the Enhanced Serving Mobile Location Centre (E-SMLC) in LTE or the Location Management Function (LMF) in 5G. This node calculates the final position estimate.

The calculated location estimate is then routed back through the chain: from the E-SMLC/LMF to the serving node (MME/SGSN/MSC), then to the GMLC, and finally delivered to the requesting LCS Client. Throughout this process, privacy is paramount. The network must verify that the LCS Client is authorized for the specific type of request and that the target subscriber's privacy settings, stored in the Home Subscriber Server (HSS) or Home Location Register (HLR), permit such a network-induced location disclosure. The NI-LR procedure is therefore a complex orchestration of authorization, signaling, radio measurement, and calculation across multiple network entities.

Purpose & Motivation

NI-LR was developed to meet critical regulatory, safety, and commercial needs that require the network to be able to locate a subscriber without their active participation. The most significant driver was regulatory mandates for emergency caller location. When a user makes an emergency call (e.g., 112, 911), the network must automatically determine the caller's location to dispatch aid, even if the caller is unable to provide it or is unaware of their position. NI-LR provides the standardized mechanism for this automatic network-triggered location.

Beyond emergencies, NI-LR addresses requirements for lawful interception and location-based services. Law enforcement agencies, with proper legal authorization, require the capability to locate a subscriber for security purposes. Commercially, it enables a wide range of value-added services. For example, a logistics company can track its fleet vehicles, a network operator can implement location-dependent charging (e.g., different rates at home vs. abroad), or a service provider can send targeted advertisements based on a user's area. Prior to standardized LCS, such capabilities would require proprietary, non-interoperable solutions. NI-LR, as part of the broader 3GPP LCS framework, created a unified, secure, and privacy-protected method for network-initiated positioning, enabling global interoperability for safety and commercial applications.