Description
Secure User Plane for Location (SUPL) is a protocol suite standardized by 3GPP and Open Mobile Alliance (OMA) that provides location services (LCS) by leveraging the user plane (IP-based data channels) rather than the control plane signaling channels. Introduced in 3GPP Release 7, SUPL enables efficient and scalable determination of a mobile device's position by transporting positioning-related messages between the SUPL Enabled Terminal (SET), which is the mobile device, and the SUPL Location Platform (SLP), which is the network-based location server. The SLP consists of two main components: the SUPL Location Center (SLC), which handles session management and privacy, and the SUPL Positioning Center (SPC), which performs position calculation.
SUPL operates by establishing a secure IP connection (using TLS/DTLS) between the SET and SLP. The protocol supports multiple positioning methods, including Assisted Global Navigation Satellite System (A-GNSS), Observed Time Difference of Arrival (OTDOA), Enhanced Cell ID (E-CID), and others. In a typical SUPL session, the SLP initiates or the SET initiates a location request. They exchange messages (using OMA-defined protocols like ULPS or LPP) to transfer assistance data (e.g., satellite ephemeris for A-GNSS) from SLP to SET and measurement data (e.g., pseudoranges or timing measurements) from SET to SLP. The SPC then computes the position, which can be returned to the SET or to an external LCS client (e.g., a navigation app or emergency service).
Key architectural elements include the SET's SUPL agent (the application requesting location), the SLP's interfaces with core network elements (like GMLC in control plane LCS), and support for roaming scenarios where the home SLP and visited SLP may collaborate. SUPL is designed to reduce signaling load on the control plane, offer faster positioning, and support continuous tracking services. It is widely deployed for commercial location-based services (e.g., maps, friend finders) and mandated for emergency services like E911 in some regions. Specifications span 3GPP (e.g., 23.271 for architecture) and OMA (e.g., OMA-AD-SUPL for protocol details), ensuring interoperability across devices and networks.
Purpose & Motivation
SUPL was developed to address limitations of control plane location solutions in 2G/3G networks, which relied on signaling system no. 7 (SS7) and circuit-switched connections. Control plane LCS was complex, slow, and not scalable for mass-market location-based services due to heavy signaling overhead and dependency on network vendor implementations. As demand for location services grew with the rise of smartphones and apps, a more efficient, IP-based approach was needed.
The primary motivation for SUPL was to leverage the user plane (packet-switched data) for location positioning, enabling faster session setup, reduced network congestion, and easier integration with Internet-based applications. By using standard IP security (TLS), SUPL also provided inherent security and privacy protections, which were less robust in control plane methods. This allowed operators to offer commercial LCS (like navigation and advertising) without impacting core network stability.
Furthermore, SUPL supported a wider range of positioning technologies (e.g., A-GNSS, Wi-Fi positioning) and allowed continuous location tracking for services like fleet management or child monitoring. Its introduction in Release 7 coincided with the growth of 3G data services, providing a future-proof framework that evolved through LTE and 5G. SUPL also facilitated regulatory compliance for emergency services (e.g., E112 in Europe) by offering a standardized, reliable method for location determination, complementing control plane solutions. Thus, SUPL solved the problems of scalability, speed, and flexibility, enabling the location-aware ecosystem we see today.
Classification
Detected Changes Across Releases
from 3GPP Change RequestsSpecific changes extracted from the „Change history“ tables of 3GPP specifications (168 CRs across 5 releases). Complements the general historical overview above with the evidence-based evolution of this function.
Studied in Rel-7, normative work from Rel-15.
In Release 15, the SUPL function was enhanced with new capabilities for high-accuracy positioning, including the introduction of support for Inertial Measurement Units (IMU) to aid OTDOA and the addition of High Accuracy location estimates. The release also expanded OTDOA assistance data for New Radio (NR) and added specific parameters like TDD UL/DL configuration and SFN offset. Furthermore, it introduced updates for distinguishing the location source when a sensor method is used and included general updates to the OMA SUPL information.
- Complete location entry definition TS 24.526CR0006
- Introduction of IMU support for OTDOA TS 36.355CR0204
- Correction to length of location sub entry in WLANSP rule TS 24.526CR0027
- Addition of High Accuracy location estimates TS 29.171CR0051
- Location header TS 29.512CR0169
- Corrections of user location and session AMBR attributes TS 29.512CR0173
+ 6 more changes
In Release 16, the SUPL enhancements included the support for concurrent location requests and the introduction of a unified location service exposure procedure. The release also clarified and improved procedures for low-power periodic and triggered location reporting, as well as the handling of NG-RAN location service exposure. Furthermore, it added support for IMS interworking for location services and incorporated the NEF function within the location service exposure framework.
- Support of Concurrent Location Request TS 23.273CR0006
- HFC node Id in Location information, TS 29.512 TS 29.512CR0390
- Correction and Improvement of Low Power Periodic and Triggered Location TS 23.273CR0011
- Handling of NG-RAN Location Service Exposure Procedure TS 23.273CR0021
- Clarification of 5GC-MT-LR procedure for the commercial location service TS 23.273CR0024
- Completion of Unified Location Service Exposure Procedure for TS 23.273 TS 23.273CR0028
+ 23 more changes
In Release 17, the SUPL function was enhanced with new capabilities including support for Scheduled Location Time, deferred location requests with Multiple QoS Class support, and location estimates provided in Local Coordinates. It also introduced requirements for GNSS integrity and a timestamp in location requests, alongside support for User Location Change reporting and the use of a requested maximum age of location. Furthermore, the release extended Location Services to apply within Standalone Non-Public Networks (SNPNs).
- Introduction of the Scheduled Location Time TS 23.273CR0187
- Addition of a Scheduled Location Time TS 23.273CR0151
- Updates to support User Location Change TS 29.512CR0629
- Add user plane lantecy requirement in PCC rule TS 29.512CR0763
- PCC Support of restricted PDU Session for remote provisioning of UE using User Plane TS 29.512CR0838
- Remove the editor's note for AF preference for the user plane latency TS 29.512CR0845
+ 28 more changes
In Release 18, the SUPL function was enhanced to support User Plane Positioning, including specific procedures for positioning over the user plane connection between the UE and LMF. It introduced support for a UE user plane connection to an LCS Client or AF for event reporting and added new capabilities for LCS user plane positioning. Furthermore, Release 18 expanded location service continuity between EPS and 5GS and introduced network verification of UE location.
- 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
- Support of User Plane Positioning TS 23.273CR0246
- Privacy Check for NWDAF requesting UE location from GMLC TS 23.273CR0249
- Verification of location for NTN access TS 23.273CR0258
+ 65 more changes
In Release 19, key SUPL enhancements introduced the Deferred 5GC-MT-LR Procedure for Periodic Location Events and added support for Multiple Location Reports for Next Generation Emergency Routing. The release also standardized the use of LMF routing information instead of an LMF ID for User Plane Connection Procedures and provided clarifications for procedures involving user plane connection establishment, modification, and maximum connections per UE.
- 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
- Use routing information to map the user plane connection in the UE TS 24.572CR0115
- Include routing information for LMF relocation on new user plane connection TS 24.572CR0116
- E-CID measurement enhancement [ECID_enh1] TS 38.305CR0195
- Support of Location Service Involving WAB-Nodes TS 38.305CR0196
+ 16 more changes
Explore further
Broader topics and technologies where SUPL plays a role.
Defining Specifications
3GPP specifications that define or reference SUPL, 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 |
| TR 22.814 va00 | Study on LCS support for non-3GPP accesses | Rel-10 |
| TS 23.167 vj11 | IMS Emergency Sessions | Rel-19 |
| TS 23.271 vj00 | LCS Stage 2 Specification | Rel-19 |
| TS 23.273 vj50 | 5G Location Services Stage 2 Architecture | Rel-19 |
| TS 23.303 vj00 | Proximity Services (ProSe) Stage 2 | 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 23.868 v900 | Study on IMS Emergency Calls | Rel-9 |
| TS 24.526 vj30 | UE Policies for 5GS; Stage 3 | Rel-19 |
| TS 24.572 vj50 | 5G LCS User Plane Protocol Specification | Rel-19 |
| TS 29.171 vj00 | LCS Application Protocol (LCS-AP) Specification | Rel-19 |
| TS 29.212 vj00 | Gx/Gxx/Sd/St Diameter Protocol | Rel-19 |
| TS 29.512 vj40 | 5G Session Management Policy Control Service | 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 36.809 vc00 | Study on RF Pattern Matching for LTE Positioning | Rel-12 |
| TS 37.355 vj20 | LTE Positioning Protocol (LPP) | Rel-19 |
| TS 37.857 vd10 | Study on Indoor Positioning Enhancements | Rel-13 |
| TS 38.305 vj00 | NG-RAN UE Positioning Stage 2 | Rel-19 |