Description
The Ranging and Sidelink Positioning Protocol (RSPP) is a protocol layer specified in 3GPP for performing ranging and positioning operations over the sidelink interface. Sidelink refers to direct communication between User Equipments (UEs) without routing data through the network infrastructure (gNB or eNB). RSPP operates within the sidelink protocol stack, interacting with layers like the Sidelink Radio Link Control (SL-RLC) and Sidelink Medium Access Control (SL-MAC). Its primary function is to facilitate the exchange of signals and messages between UEs to estimate the distance (ranging) and determine relative or absolute positions (positioning).
RSPP works by defining procedures for measurement and reporting. UEs exchange specific reference signals or packets designed for time-of-arrival (ToA), time-difference-of-arrival (TDoA), or angle-of-arrival (AoA) measurements. The protocol manages the scheduling of these signals, the collection of measurement data, and the calculation of range or position. It supports both one-way and two-way ranging techniques. In two-way ranging, for example, UE A sends a ranging request, UE B responds, and UE A calculates the round-trip time to estimate distance, with RSPP handling the message sequence and timing. The protocol may also support multi-lateration where multiple UEs collaborate to determine a target UE's location.
Key components of RSPP include the definition of sidelink positioning reference signals (SL-PRS), control messages for initiating and coordinating ranging sessions, and measurement reports. It interfaces with higher-layer positioning services and applications. RSPP's role is critical in scenarios where GNSS signals are unavailable or unreliable, such as indoors, in urban canyons, or during emergencies. By leveraging direct UE-to-UE communication, it enables decentralized positioning solutions that are resilient, low-latency, and can operate with partial or no network coverage, enhancing services like vehicle platooning, pedestrian safety, and asset tracking.
Purpose & Motivation
RSPP was introduced in 3GPP Release 18 to address the need for accurate, infrastructure-independent positioning in sidelink communication scenarios. Prior positioning methods in cellular networks primarily relied on uplink/downlink signals between UEs and base stations (e.g., OTDOA, UTDOA) or GNSS. These methods have limitations in environments without network coverage or where GNSS is denied. The proliferation of V2X (Vehicle-to-Everything) and advanced sidelink applications created a demand for relative positioning between nearby devices to support collision avoidance, cooperative driving, and formation keeping.
The protocol solves the problem of standardizing how UEs directly measure distances and positions between each other over the PC5 interface. Before RSPP, proprietary or non-standardized methods could lead to interoperability issues. RSPP provides a unified, 3GPP-specified framework, ensuring that UEs from different manufacturers can perform ranging and positioning reliably. It was motivated by use cases in autonomous vehicles, public safety (e.g., locating first responders in a building), and commercial applications like social networking or augmented reality games requiring proximity detection. By integrating positioning capabilities directly into the sidelink protocol stack, RSPP enhances the autonomy and functionality of device-to-device communication systems.
Classification
Detected Changes Across Releases
from 3GPP Change RequestsSpecific changes extracted from the „Change history“ tables of 3GPP specifications (139 CRs across 5 releases). Complements the general historical overview above with the evidence-based evolution of this function.
In Release 15, the Ranging and Sidelink Positioning Protocol (RSPP) function was introduced to specify the stage 2 architecture for ranging-based services and sidelink positioning in the 5G System. It defined new operational modes, including Network-based, Network-assisted, and UE-only operation, and introduced key roles such as the SL Positioning Server UE and SL Positioning Client UE for service coordination over PC5 interfaces.
- Gaps for positioning measurements TS 38.305CR0002
- CR to 38.305 on use of positioning measurement gaps for subframe and slot timing detection towards E-UTRA TS 38.305CR0008
- Corrections for Positioning Architecture TS 38.305CR0015
- - correction to ASN.1: addiming a missing change to "WriteReplaceWarningResponseIEs F1AP-PROTOCOL-IES ::= {" TS 38.473
In Release 16, the new RSPP function introduced the architecture and protocols for Sidelink Positioning and Ranging services over the PC5 interface, supporting network-based, network-assisted, and UE-only operational modes. It defined roles such as Target UE, SL Reference UE, and SL Positioning Server UE to enable location, relative positioning, and ranging between devices. The specification also established procedures for service initiation by various entities including UEs, network functions, and application functions.
- Introduction of NR positioning TS 38.305CR0017
- Introduction of NR positioning TS 38.305CR0034
- Update of the NRPPa Transport procedure to support NR positioning TS 38.413CR0396
- Introduction of positioning support over F1AP TS 38.473CR0495
- Corrections to NR Positioning TS 38.305CR0025
- Correction to SUPL support for NR positioning methods TS 38.305CR0028
+ 12 more changes
In Release 17, the new RSPP (Ranging and Sidelink Positioning Protocol) function introduced standardized support for Ranging based services and Sidelink Positioning over the PC5 interface. This enabled new UE-only, network-assisted, and network-based operational modes for determining relative location, distance, and direction between UEs. The release specifically defined roles like SL Positioning Server UE and procedures for scenarios including in-coverage, partial-coverage, and out-of-coverage of the 5G network.
- Introduction of R17 Positioning Enhancements TS 38.305CR0086
- Introduction of NR positioning enhancements to NGAP TS 38.413CR0754
- Exchange of protocol support at target RAN node for NG handover [PROT_SUP] TS 38.413CR0800
- Introduction of Sidelink Relay over Xn TS 38.423CR0693
- (BL CR to TS 38.423) Transfer of Positioning Context in XnAP TS 38.423CR0748
- Introduction of NR Positioning enhancements TS 38.473CR0803
+ 17 more changes
In Release 18, the RSPP function introduced new control plane procedures for network-integrated service handling, including Mobile Terminated Location Requests and UL/DL Supplementary Service messages between the LMF and UE for Ranging/SL. It also defined a specific NAS transport mechanism for RSPP and enhanced privacy with a dedicated sidelink positioning privacy check procedure. Furthermore, the release provided clarifications and corrections on capability signaling, architecture figures, and the operational modes for UE-based and network-assisted sidelink positioning.
- Sidelink positioning privacy check procedure TS 24.514CR0001
- NAS protocol supports LCS PRU messages TS 24.571CR0017
- NAS transport for RSPP TS 24.571CR0047
- Procedure for Ranging/SL Positioning service exposure through 5GC network via control plane TS 24.571CR0069
- UL Supplementary service message between LMF and UE for Ranging_SL TS 24.571CR0071
- DL Supplementary service message between LMF and UE for Ranging_SL TS 24.571CR0070
+ 77 more changes
In Release 19, the RSPP function introduced Artificial Intelligence/Machine Learning (AIML) Positioning as a new capability. The release also included corrections and clarifications to several key procedures, such as the positioning activation and deactivation procedure, the sidelink positioning service request for the located UE, and the required QoS for positioning. Additionally, enhancements were made to the description of SLPP transport initiation and the roles within the RSPP metadata of the PROSE PC5 DISCOVERY message.
- Introduction of AIML Positioning TS 38.305CR0190
- Corrections on located UE in sidelink positioning service request procedure TS 24.514CR0035
- Clarification on description of sidelink positioning SLPP transport initiation TS 24.514CR0036
- Clarification on required QoS for located UE(s) positioning TS 24.514CR0058
- Clarification on roles in RSPP metadata of the PROSE PC5 DISCOVERY message TS 24.514CR0061
- Corrections on AIML Positioning TS 38.305CR0197
+ 5 more changes
Explore further
Broader topics and technologies where RSPP plays a role.
Defining Specifications
3GPP specifications that define or reference RSPP, with the latest known release. Sourced from the 3GPP document catalog — see methodology.
| Specification | Title | Release |
|---|---|---|
| TS 23.586 vj00 | Ranging & Sidelink Positioning in 5GS | Rel-19 |
| TS 24.514 vj30 | Ranging & Sidelink Positioning in 5GS | Rel-19 |
| TS 24.571 vj20 | Control Plane LCS Procedures | Rel-19 |
| TS 33.533 vj00 | Security for 5G Ranging & Sidelink Positioning | Rel-19 |
| TS 38.305 vj00 | NG-RAN UE Positioning Stage 2 | Rel-19 |
| TS 38.413 vj10 | NG Application Protocol (NGAP) | Rel-19 |
| TS 38.423 vj10 | Xn Application Protocol (XnAP) specification | Rel-19 |
| TS 38.473 vj10 | 5G F1 Application Protocol (F1AP) | Rel-19 |