Description
The LTE Positioning Protocol (LPP) is a key application-layer protocol within the 3GPP control plane architecture, specifically designed for transferring positioning-related information. It operates between a Location Server (LS), such as the Evolved Serving Mobile Location Centre (E-SMLC) in LTE or the Location Management Function (LMF) in 5GC, and a target User Equipment (UE). LPP is carried over the LTE-Uu and SLg interfaces via NAS transport, ensuring secure and reliable delivery of positioning commands and measurements. The protocol is inherently capability-aware; an LPP session typically begins with the server querying the UE for its supported positioning methods (e.g., Observed Time Difference of Arrival - OTDOA, Assisted Global Navigation Satellite System - A-GNSS, Enhanced Cell ID - E-CID) and related capabilities, allowing the server to select the most appropriate technique for the requested accuracy and environment.
LPP messages are structured into several procedure types. The main procedures are: Capability Transfer, where the UE informs the server of its supported positioning methods; Assistance Data Transfer, where the server can provide the UE with data (like GNSS ephemeris or OTDOA reference cell information) to improve positioning speed and accuracy; and Location Information Transfer, which can be either network-initiated (the server requests measurements or a position estimate) or UE-initiated (the UE provides its location). For OTDOA, the server provides assistance data listing neighboring cells and their positioning reference signal (PRS) configurations. The UE then measures the Reference Signal Time Difference (RSTD) between these cells and reports them back via LPP for the server to calculate the position.
In the 5G system, LPP continues to be the primary positioning protocol, now between the UE and the LMF. Its architecture has been extended to support new 5G NR positioning reference signals (PRS for DL-TDOA, SRS for UL-TDOA) and techniques like Multi-RTT (Round Trip Time). LPP messages are transported over the NG control plane (NG-C) interface via 5G NAS. The protocol supports both real-time positioning for services like emergency calls and deferred or periodic positioning for tracking applications. Its design is modular and extensible, allowing new positioning methods and measurement types to be added in subsequent 3GPP releases without overhauling the core protocol, ensuring it remains the future-proof foundation for cellular-based positioning services.
Purpose & Motivation
LPP was created to provide a standardized, efficient, and accurate method for determining the location of LTE devices, addressing regulatory requirements like Enhanced 911 (E911) and enabling commercial location-based services (LBS). Prior to LPP, location services in 2G/3G relied on less accurate methods like Cell-ID or used proprietary protocols, leading to fragmentation and inconsistent performance. The development of LTE provided an opportunity to design a unified, IP-based positioning protocol from the ground up.
The protocol was motivated by the need for high accuracy, low latency, and minimal impact on UE battery life. It solves the problem of how to coordinate complex positioning measurements (which require precise timing and signal information) between the network and potentially millions of devices. By supporting assistance data transfer, LPP allows UEs to acquire GNSS signals faster (A-GNSS) or perform OTDOA measurements more accurately, significantly improving performance compared to standalone methods. Its creation enabled a wide range of applications beyond emergency services, including turn-by-turn navigation, asset tracking, geofencing, and location-aware network optimization, making precise positioning a core capability of modern cellular networks.
Classification
Detected Changes Across Releases
from 3GPP Change RequestsSpecific changes extracted from the „Change history“ tables of 3GPP specifications (225 CRs across 5 releases). Complements the general historical overview above with the evidence-based evolution of this function.
Studied in Rel-9, normative work from Rel-15.
In Release 15, the LPP function was enhanced with new capabilities including support for Inertial Measurement Unit (IMU) data to improve OTDOA, the addition of broadcast positioning assistance data, and specific support for OTDOA within NB-IoT. The release also introduced new assistance data elements such as TDD UL/DL configuration and SFN offset for OTDOA, alongside protocol clean-up and corrections. Furthermore, it defined new UE capabilities for LPP within the 5GMM capability information element and procedures for the delivery of LPP messages via NAS transport.
- Introduction of IMU support for OTDOA TS 36.355CR0204
- Addition of broadcast of positioning assistance data TS 36.355CR0207
- Positioning SIB value tag and expiration time TS 36.355CR0226
- Support of OTDOA in NB-IoT enhancement TS 36.455CR0093
- Fixes for CP protocol stack TS 23.501CR0083
- Correction on Control Plane protocol stacks TS 23.501CR0240
+ 23 more changes
In Release 16, key LPP enhancements included the introduction of NR positioning capabilities to support New Radio, the addition of SSR (State Space Representation) positioning support for LTE, and the integration of the BDS (BeiDou) B1C signal for A-GNSS. These updates expanded the protocol's support for modernized positioning techniques and new global navigation satellite systems.
- Protocol stack for W-5GAN support TS 23.501CR0961
- Port management information container: Delivery via the NAS protocol and coding TS 24.501CR1470
- CR for TS36.171, Introduction of BDS B1C in A-GNSS TS 36.171CR0020
- Introduction of B1C signal in BDS system in A-GNSS TS 36.305CR0083
- CR for the introduction of SSR positioning support into LTE TS 36.305CR0085
- Introduction of B1C signal in BDS system in A-GNSS TS 37.355CR0248
+ 47 more changes
In Release 17, the LPP (LTE Positioning Protocol) was enhanced with specific new capabilities, including support for B2a and B3I signals from the BDS (BeiDou) system and for NavIC L5 A-GNSS, as well as the introduction of GNSS Positioning Integrity. These updates were implemented through a series of Change Requests focused on LPP updates, corrections to the protocol's capabilities, and ASN.1 corrections.
- 5GSM protocol update for redundant PDU sessions TS 24.501CR3671
- Introduction of B2a and B3I signal in BDS system and GNSS Positioning Integrity TS 36.305CR0107
- Introduction of R17 Positioning Enhancements in LPP TS 37.355CR0332
- Introduction of R17 Positioning Enhancements TS 38.305CR0086
- Introduction of NR Positioning enhancements to NRPPa TS 38.455CR0037
- Adding PDU session limitation and protocol stacks for trusted WLAN access for N5CW device TS 23.501CR2991
+ 30 more changes
In Release 18, key enhancements to LPP included the introduction of sidelink (SL) positioning support, enabling direct positioning between devices over the PC5 interface. It also added support for user plane positioning capability indication and introduced new procedures for ranging and sidelink positioning service exposure through the 5G core network. Furthermore, the release expanded NR positioning capabilities and enabled location information reporting with periodicities below one second.
- Support of SL Positioning TS 23.501CR4555
- User plane positioning capability indication TS 24.501CR5015
- Protocol error handling enhancements for Type 6 IE container IEs TS 24.501CR5031
- Transmission of Ranging/SL Positioning Policy TS 24.501CR5197
- User plane positioning capability TS 24.501CR5285
- UL/DL NAS transport updates for user plane positioning TS 24.501CR5215
+ 69 more changes
In Release 19, the LPP protocol was enhanced to introduce support for new global navigation satellite systems (GNSS) signals, specifically the NavIC L1 SPS and BDS B2b signals for A-GNSS positioning. Furthermore, the release introduced foundational work for AI/ML-based positioning accuracy enhancements within the positioning framework. These updates expanded the protocol's capabilities for more accurate and diverse location services.
- Control Plane and User Plane Protocol stacks involving the MWAB node TS 23.501CR5561
- General description of relaying media related information over N6 using an encapsulation protocol TS 23.501CR5711
- NWDAF model provision for AI positioning TS 23.501CR5635
- CR for TS 36.171 to introduce BDS B2b signal in A-GNSS TS 36.171CR0032
- 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
+ 26 more changes
Explore further
Broader topics and technologies where LPP plays a role.
Defining Specifications
3GPP specifications that define or reference LPP, with the latest known release. Sourced from the 3GPP document catalog — see methodology.
| Specification | Title | Release |
|---|---|---|
| TR 21.905 vj00 | 3GPP Technical Terms and Definitions | Rel-19 |
| TS 23.501 vk00 | 5G System Architecture Stage 2 | Rel-20 |
| TS 23.586 vj00 | Ranging & Sidelink Positioning in 5GS | 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 24.501 vj50 | 5G NAS Protocols Specification | Rel-19 |
| TS 24.571 vj20 | Control Plane LCS Procedures | Rel-19 |
| TS 24.572 vj50 | 5G LCS User Plane Protocol Specification | Rel-19 |
| TS 24.890 vg00 | 5G NAS Protocol for 5GS Stage 3 | Rel-16 |
| TS 29.171 vj00 | LCS Application Protocol (LCS-AP) Specification | Rel-19 |
| TS 33.814 vg01 | Security aspects of enhanced Location Services (eLCS) | Rel-16 |
| TS 36.133 vj20 | E-UTRA RRM Requirements | Rel-19 |
| TS 36.171 vj10 | A-GNSS Minimum Performance Requirements for UE | 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 36.455 vj00 | LTE Positioning Protocol Annex (LPPa) | Rel-19 |
| TS 36.809 vc00 | Study on RF Pattern Matching for LTE Positioning | Rel-12 |
| TS 36.855 vd00 | E-UTRA Positioning Enhancements Study | Rel-13 |
| TS 37.171 vj00 | UE Positioning Performance Requirements | Rel-19 |
| TS 37.355 vj20 | LTE Positioning Protocol (LPP) | Rel-19 |
| TS 37.571 vj00 | UE Conformance for Positioning | Rel-19 |
| TS 37.857 vd10 | Study on Indoor Positioning Enhancements | Rel-13 |
| TS 38.171 vj10 | 5G A-GNSS UE Positioning Requirements | Rel-19 |
| TS 38.305 vj00 | NG-RAN UE Positioning Stage 2 | Rel-19 |
| TS 38.455 vj10 | NR Positioning Protocol A (NRPPa) | Rel-19 |
| TS 38.843 vj00 | Study on AI/ML for NR Air Interface | Rel-19 |
| TS 38.855 vg00 | Study on NR Positioning Support | Rel-16 |