Description
A Location Information Request (LIR) is a core procedural element within 3GPP architectures for obtaining the position of a mobile device. It is not a single protocol message but a conceptual service request that is realized through specific protocols and interfaces, such as the LTE Positioning Protocol (LPP) over the SLs interface, or the OMA SUPL protocol, or via core network interfaces like the Gateway Mobile Location Centre (GMLC) using the Le or SLg interfaces. An LIR is initiated by a Location Service (LCS) Client, which could be an external application (e.g., a mapping service), an internal network service (e.g., for lawful interception), or the UE itself. The request contains parameters such as the target UE's identifier (MSISDN, IMSI), the required Quality of Service (QoS) for the location (e.g., accuracy, response time), and the type of location information needed (e.g., geographic coordinates, civic address).
Upon receiving an LIR, the network's location system engages the appropriate positioning methods. For network-based positioning, the network may use measurements from base stations (e.g., Observed Time Difference of Arrival - OTDOA in LTE, Downlink Time Difference of Arrival - DL-TDOA in 5G). For UE-based positioning, the network provides assistance data (e.g., satellite ephemeris for A-GNSS) to the UE, which then computes its own fix and may report it back. Hybrid methods combine both. The control and coordination of this process are managed by network entities like the Evolved Serving Mobile Location Centre (E-SMLC) in LTE or the Location Management Function (LMF) in 5G. These entities select the positioning method based on the LIR's QoS, UE capabilities, and available network measurements.
The result of processing an LIR is a Location Information Response, which delivers the estimated location data to the requesting client. The entire procedure involves multiple network domains: the core network for client authorization and request routing, the radio access network for measurement collection, and potentially the UE. Privacy is a critical aspect; the network must verify that the LCS Client is authorized to request the location of the specific target UE, based on subscriber privacy settings and regulatory rules. The LIR mechanism is thus the triggering event for a complex, standardized sequence that transforms radio signals or satellite data into a usable geographic location for services.
Purpose & Motivation
The concept of the Location Information Request emerged to standardize how applications and services could programmatically obtain a mobile subscriber's location. Before its standardization, location services were proprietary and fragmented, hindering the development of widespread location-based applications. The primary problem it solves is providing a unified, secure, and reliable interface for authorized entities to request UE location, which is essential for commercial services (friend-finder, location-based advertising), emergency services (E-911/112), and network optimization.
Historically, the need was driven by regulatory mandates for emergency caller location and the commercial potential of location-based services. The LIR framework, evolving since 3GPP Release 99, created a clear architectural separation between the entity requesting location (the LCS Client) and the network's positioning capabilities. This addressed the limitations of ad-hoc solutions by defining standardized protocols (e.g., LPP, SUPL), interfaces (e.g., Le, SLg), and privacy control mechanisms. It enabled a ecosystem where network operators could expose location capabilities to third-party application providers in a controlled manner, fueling innovation in mobile services while ensuring subscriber privacy and network security.
Detected Changes Across Releases
from 3GPP Change RequestsSpecific changes extracted from the „Change history“ tables of 3GPP specifications (256 CRs across 5 releases). Complements the general historical overview above with the evidence-based evolution of this function.
In Release 15, the Location Information Request (LIR) function was enhanced with clarifications on location information in immediate reports and the derivation and delivery of location data. It introduced specific new data elements for positioning, such as barometric pressure and altitude, into the Provide Positioning Information procedure. Furthermore, the release standardized the inclusion of a location header within relevant signaling messages and redirect responses.
- Remove AN Type from N1/N2 Message Transfer Request TS 29.518CR0008
- Location Service ProvideLocationInfo TS 29.518CR0019
- Location Service ProvidePositioningInfo TS 29.518CR0020
- Passing NSSF information in N1MessageNotification TS 29.518CR0047
- Clarification on location information in immediate report TS 29.518CR0049
- Correct reference for Event Report Information TS 29.518CR0051
+ 9 more changes
In Release 16, the LIR function was enhanced to support a Commercial and Deferred 5GC-MT-LR procedure and a Unified Location Service Exposure Procedure, as detailed in TS 23.273. It also introduced the capability for the AMF to forward location services messages between the UE and LMF and clarified the handling of the NG-RAN Location Service Exposure Procedure. Furthermore, improvements were made for low power periodic and triggered location and for enhanced location update reporting with Dual Connectivity.
- Support of Concurrent Location Request TS 23.273CR0006
- CreateUEContext – I-SMF and SM Context ID Information TS 29.518CR0194
- Transfer Information of MA PDU Session between AMFs TS 29.518CR0211
- Target Access type in N1N2MessageTransfer Request for a MA PDU session TS 29.518CR0229
- RIM Information Transfer procedure TS 29.518CR0240
- User location report TS 29.518CR0241
+ 50 more changes
In Release 17, key enhancements to the Location Information Request (LIR) function included the introduction of a **Scheduled Location Time** capability, allowing for deferred location requests, and the provision of **Higher Resolution Timestamps for Location Estimates**. Furthermore, new features such as **Location estimate in Local Coordinates** and support for **UE Location Trends Event** reporting were added to increase the flexibility and richness of location-based services.
- Introduction of the Scheduled Location Time TS 23.273CR0187
- Addition of a Scheduled Location Time TS 23.273CR0151
- NF discovery based on SUCI information TS 29.518CR0444
- PRA Information update TS 29.518CR0483
- Add Local location TS 29.518CR0533
- Analytics subscription information TS 29.518CR0536
+ 53 more changes
In Release 18, the LIR function was enhanced to support multiple location reports for a single Mobile-Terminated Location Request (MT-LR) for regulatory services and to enable location reporting only when the UE is within a target area defined with finer granularity. It also introduced support for Mobile Base Station Relays (MBSR) within MT-LR procedures and ensured location service bi-directional continuity between EPS and 5GS. Furthermore, Release 18 added a privacy check for an NWDAF requesting UE location from a GMLC and introduced verification of location for Non-Terrestrial Network (NTN) access.
- Multiple location report for MT-LR Immediate Location Request for the regulatory service TS 23.273CR0237
- Support of Mobile Base Station Relay for Location Service TS 23.273CR0240
- UE location reporting only when the UE locates in the target area defined with finer granularity TS 23.273CR0242
- Privacy Check for NWDAF requesting UE location from GMLC TS 23.273CR0249
- Verification of location for NTN access TS 23.273CR0258
- Enhance the Triggered Location for UE power saving purpose TS 23.273CR0271
+ 91 more changes
In Release 19, the LIR function was enhanced with new capabilities including a deferred procedure for periodic location events using NRPPa measurement reports, support for multiple location reports for next-generation emergency routing, and the introduction of a UE location trends report at RAN node granularity. It also added cell radio and coarse location information to location structures, clarified the use of LMF routing information instead of an LMF ID for User Plane procedures, and introduced LMF routing information to the N1N2MessageTransfer service operation.
- Adding Deferred 5GC-MT-LR Procedure for Periodic Location Events based NRPPa Periodic Measurement Reports TS 23.273CR0589
- Multiple Location Report for Next Generation Emergency Routing TS 23.273CR0608
- UE Location Trends Report at RAN Node Granularity TS 29.518CR1162
- Clarification on Storage and Transfer of Access and Mobility Management Policy Information in UE Context TS 29.518CR1181
- Location acquisition based on measurement reporting TS 33.127CR0241
- Extra IAB information in stage 2 related to Downlink NAS transport and to UE CONTEXT MODIFICATION REQUEST TS 33.127CR0255
+ 23 more changes
Explore further
Broader topics and technologies where LIR plays a role.
Defining Specifications
3GPP specifications that define or reference LIR, with the latest known release. Sourced from the 3GPP document catalog — see methodology.
| Specification | Title | Release |
|---|---|---|
| TS 03.071 v7b0 | Location Services (LCS) Stage 2 Description | Rel-7 |
| TS 23.171 v1300 | LCS Stage 2 Specification for UMTS | Rel-4 |
| TS 23.271 vj00 | LCS Stage 2 Specification | Rel-19 |
| TS 23.273 vj50 | 5G Location Services Stage 2 Architecture | Rel-19 |
| TS 23.380 vj10 | IMS Restoration Procedures | Rel-19 |
| TS 29.518 vj50 | AMF Service Based Interface Protocol | Rel-19 |
| TS 29.572 vj50 | Nlmf Service Based Interface Stage 3 | Rel-19 |
| TR 29.949 vj00 | VoLTE IMS Roaming Architecture & Procedures | Rel-19 |
| TS 32.808 v1800 | Common User Profile Storage Framework | Rel-8 |
| TS 33.127 vj50 | Lawful Interception Architecture and Functions | Rel-19 |
| TS 33.128 vj50 | 3GPP TS 33.128: Lawful Interception Protocols | Rel-19 |