Description
Mobile Originated Location Request (MO-LR) is a procedure within the 3GPP Location Services (LCS) architecture that enables a User Equipment (UE) to act as a LCS Client, initiating a request to determine its own location or the location of another specified target UE. The process involves signaling between the UE, the serving core network, and the Location Management Function (LMF) in 5G or the Evolved Serving Mobile Location Centre (E-SMLC) in LTE. The UE sends a location request via a dedicated LCS protocol message over the control plane.
Upon receiving an MO-LR request, the network authenticates and authorizes the requesting UE based on subscriber profiles. For a self-location request, the network then invokes the appropriate positioning method. This could be network-based (e.g., Observed Time Difference of Arrival - OTDOA in LTE, Downlink Time Difference of Arrival - DL-TDOA in NR), UE-based (using assistance data like GPS/GNSS), or hybrid methods. The serving node (MME/AMF) coordinates with the positioning server (E-SMLC/LMF) which calculates the location estimate. The resulting position (latitude, longitude, accuracy) is then delivered back to the requesting UE in a location response message.
If the request is for another target UE (subject to privacy verification), the network performs a location request towards that target (akin to a Mobile Terminated Location Request - MT-LR), obtains the location, and returns it to the originating UE. Key architectural components include the LCS Client in the UE, the LCS protocol in the NAS layer, the core network control node (MSC, SGSN, MME, AMF), the positioning server (SMLC, E-SMLC, LMF), and the radio access network which provides measurement data (e.g., PRS measurements for OTDOA).
The role of MO-LR in the network is to support user-centric location-based services (LBS). It empowers the end-user to actively retrieve location information, differentiating it from network-initiated or emergency location services. It is a fundamental enabler for commercial applications, providing the standardized control-plane mechanism for devices to obtain their own coordinates for use in mapping, social networking, asset tracking, and augmented reality applications. The procedure includes privacy safeguards, requiring user consent and authorization checks.
Purpose & Motivation
MO-LR was developed to standardize a method for mobile devices to actively request location information from the network, enabling a wide range of user-driven location-based services. Prior to standardized LCS, location capabilities were proprietary or limited to network-initiated services (e.g., for lawful intercept). The creation of MO-LR addressed the growing market demand for applications like turn-by-turn navigation, location-aware search, and person-to-person location sharing.
It solved the problem of providing a reliable, secure, and operator-controlled mechanism for devices to obtain accurate positioning. Without MO-LR, applications would rely solely on onboard GPS, which has limitations indoors, in urban canyons, and for devices without GPS hardware. MO-LR leverages network-based positioning methods (e.g., cell-ID, OTDOA) and assisted-GNSS (A-GNSS) to provide faster, more accurate, and more battery-efficient location fixes than standalone GPS.
The technology was motivated by the commercial potential of LBS and the need for interoperability across devices and networks. It provided a standardized API of sorts within the network signaling, allowing application developers to build services knowing that a consistent method to retrieve location existed. It also introduced necessary privacy controls, ensuring that a user's location could not be retrieved by another party without authorization, balancing service innovation with subscriber protection.
Classification
Detected Changes Across Releases
from 3GPP Change RequestsSpecific changes extracted from the „Change history“ tables of 3GPP specifications (172 CRs across 5 releases). Complements the general historical overview above with the evidence-based evolution of this function.
In Release 15, the MO-LR function was enhanced with new capabilities for high-accuracy positioning, including the introduction of IMU (Inertial Measurement Unit) support for OTDOA and the addition of High Accuracy location estimates. The release also expanded OTDOA assistance data for NR (New Radio) and introduced mechanisms to distinguish the location source when a sensor method is used. Furthermore, enhancements were made to provide location information in both trusted and untrusted WLAN access scenarios.
- Enhance location information in trusted and untrusted WLAN TS 32.251CR0503
- Introduction of IMU support for OTDOA TS 36.355CR0204
- Addition of High Accuracy location estimates TS 29.171CR0051
- OTDOA Assistance Data Request for NR TS 36.355CR0222
- Addition of TDD UL/DL configuration to OTDOA assistance data TS 36.355CR0213
- SFN offset for OTDOA TS 36.355CR0229
+ 1 more changes
In Release 16, key enhancements for the MO-LR function included the completion and clarification of the 5GC-MO-LR procedure for the 5G core network, as detailed in TS 23.273. This release also introduced support for concurrent location requests and added operations for location privacy settings, improving service flexibility and user control. Furthermore, corrections and procedural improvements were made to ensure robustness and consistency in the MO-LR operations.
- Support of Concurrent Location Request TS 23.273CR0006
- Adding Location Privacy Setting operation TS 24.571CR0001
- Introduction of B1C signal in BDS system in A-GNSS TS 36.305CR0083
- Introduction of B1C signal in BDS system in A-GNSS TS 37.355CR0248
- Introduction of B1C signal in BDS system in A-GNSS TS 38.305CR0013
- Clarification on positioning access selection in the 5GC-MO-LR procedure TS 23.273CR0008
+ 41 more changes
In Release 17, the MO-LR function was enhanced with the introduction of a **Scheduled Location Time** for deferred and periodic requests. It also added support for delivering **Assistance Data** directly within the 5G-MO-LR procedure and introduced the capability for **Location Estimates in Local Coordinates**.
- Introduction of the Scheduled Location Time TS 23.273CR0187
- Addition of a Scheduled Location Time TS 23.273CR0151
- Periodic and Triggered 5GC-MT-LR Procedure in RRC INACTIVE state TS 23.273CR0228
- Additional of Scheduled Location Time TS 24.571CR0012
- Higher Resolution Timestamp for Location Estimates TS 29.515CR0059
- Schedule location time for GMLC TS 29.515CR0072
+ 23 more changes
In Release 18, the key new feature for MO-LR was the introduction of the **SL-MO-LR procedure** for Ranging and Sidelink Positioning, enabling a mobile station to originate a location request specifically for direct device-to-device positioning. This release also defined the handling of an **SL-MO-LR response in case of network congestion**, ensuring service robustness. Additionally, the **Ranging and Sidelink Positioning MO-LR procedure** was formally standardized, expanding the positioning mechanisms available to the mobile station beyond traditional network-based methods.
- 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
- Support of a UE user plane connection to an LCS Client or AF for periodic or triggered 5GC-MT-LR event reporting TS 23.273CR0264
+ 54 more changes
In Release 19, the MO-LR (Mobile Originated Location Request) function was enhanced by introducing a converged charging message flow specific to the 5GC-MO-LR procedure. Furthermore, support was added for new global navigation satellite systems within the A-GNSS framework, specifically the introduction of NavIC L1 SPS and BDS B2b signals for improved positioning assistance. The release also included corrections and clarifications to procedures involving sidelink positioning and WAB/MWAB nodes.
- 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
- Add message flow of converged charging for 5GC-MT-LR TS 32.271CR0031
- Add message flow of converged charging for 5GC-MO-LR TS 32.271CR0032
- Introduction of NavIC L1 SPS A-GNSS in LTE Stage 2 specification TS 36.305CR0120
- Introduction of BDS B2b in A-GNSS TS 36.305CR0121
+ 23 more changes
Explore further
Broader topics and technologies where MO-LR plays a role.
Defining Specifications
3GPP specifications that define or reference MO-LR, 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 |
| TR 21.905 vj00 | 3GPP Technical Terms and Definitions | Rel-19 |
| 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 23.700 vk00 | XR Services Application Enablement Layer | Rel-20 |
| TR 23.730 ve00 | Study on extended CIoT architecture | Rel-14 |
| TS 24.171 vj00 | NAS Protocol for LCS in E-UTRAN | Rel-19 |
| TS 24.514 vj30 | Ranging & Sidelink Positioning in 5GS | Rel-19 |
| TS 24.571 vj20 | Control Plane LCS Procedures | Rel-19 |
| TS 29.171 vj00 | LCS Application Protocol (LCS-AP) Specification | Rel-19 |
| TS 29.515 vj50 | Ngmlc Service Based Interface Protocol | Rel-19 |
| TS 29.522 vj40 | 5G NEF Northbound APIs Stage 3 | Rel-19 |
| TS 32.250 vj00 | Circuit Switched Offline Charging | Rel-19 |
| TS 32.251 vj00 | PS Domain Charging Management | Rel-19 |
| TS 32.271 vj20 | 3GPP LCS Charging Management Spec | Rel-19 |
| TS 32.272 vj00 | Charging for Push-to-Talk over Cellular (PoC) | Rel-19 |
| TS 32.293 vj00 | Proxy Function in Domestic Service Provider | Rel-19 |
| TS 36.305 vj00 | UE Positioning in E-UTRAN Stage 2 | Rel-19 |
| TS 36.355 vj00 | LTE Positioning Protocol (LPP) | Rel-19 |
| TS 37.355 vj20 | LTE Positioning Protocol (LPP) | Rel-19 |
| TS 37.571 vj00 | UE Conformance for Positioning | Rel-19 |
| TS 38.305 vj00 | NG-RAN UE Positioning Stage 2 | Rel-19 |
| TS 38.856 vg00 | Study on local NR positioning in NG-RAN | Rel-16 |
| TR 38.857 vh00 | Study on NR Positioning Enhancements | Rel-17 |