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From Concept to Reality: 5G Positioning with Open-Source Implementation of UL-TDoA in OpenAirInterface

Adeel Malik, Mohsen Ahadi, Florian Kaltenberger, Klaus Warnke, Nguyen Tien Thinh, Nada Bouknana, Cedric Thienot, Godswill Onche, Sagar Arora

TL;DR

This work tackles the challenge of delivering precise 5G UE positioning via UL-TDoA in an accessible, open-source framework. It presents a complete, 3GPP-compliant UL-TDoA implementation integrated into both the RAN and CN components of OpenAirInterface, including NRPPa messaging, LMF/AMF coordination, and end-to-end ToA/TDoA processing. The authors validate their solution with two setups—a controlled OAI-RF simulator and a real-world O-RAN Eurecom testbed—demonstrating viable positioning performance and practical integration. By releasing the implementation and documentation, this work lowers barriers to research and fosters collaboration, accelerating the development of open, flexible 5G positioning technologies.

Abstract

This paper presents, for the first time, an open-source implementation of the 3GPP Uplink Time Difference of Arrival (UL-TDoA) positioning method using the OpenAirInterface (OAI) framework. UL-TDoA is a critical positioning technique in 5G networks, leveraging the time differences of signal arrival at multiple base stations to determine the precise location of User Equipment (UE). This implementation aims to democratize access to advanced positioning technology by integrating UL-TDoA capabilities into both the Radio Access Network (RAN) and Core Network (CN) components of OAI, providing a comprehensive and 3GPP-compliant solution. The development includes the incorporation of essential protocol procedures, message flows, and interfaces as defined by 3GPP standards. Validation is conducted using two distinct methods: an OAI-RF simulator-based setup for controlled testing and an O-RAN-based Localization Testbed at EURECOM in real-world conditions. The results demonstrate the viability of this open-source UL-TDoA implementation, enabling precise positioning in various environments. By making this implementation publicly available, the study paves the way for widespread research, development, and innovation in the field of 5G positioning technologies, fostering collaboration and accelerating the advancement of cellular network positioning.

From Concept to Reality: 5G Positioning with Open-Source Implementation of UL-TDoA in OpenAirInterface

TL;DR

This work tackles the challenge of delivering precise 5G UE positioning via UL-TDoA in an accessible, open-source framework. It presents a complete, 3GPP-compliant UL-TDoA implementation integrated into both the RAN and CN components of OpenAirInterface, including NRPPa messaging, LMF/AMF coordination, and end-to-end ToA/TDoA processing. The authors validate their solution with two setups—a controlled OAI-RF simulator and a real-world O-RAN Eurecom testbed—demonstrating viable positioning performance and practical integration. By releasing the implementation and documentation, this work lowers barriers to research and fosters collaboration, accelerating the development of open, flexible 5G positioning technologies.

Abstract

This paper presents, for the first time, an open-source implementation of the 3GPP Uplink Time Difference of Arrival (UL-TDoA) positioning method using the OpenAirInterface (OAI) framework. UL-TDoA is a critical positioning technique in 5G networks, leveraging the time differences of signal arrival at multiple base stations to determine the precise location of User Equipment (UE). This implementation aims to democratize access to advanced positioning technology by integrating UL-TDoA capabilities into both the Radio Access Network (RAN) and Core Network (CN) components of OAI, providing a comprehensive and 3GPP-compliant solution. The development includes the incorporation of essential protocol procedures, message flows, and interfaces as defined by 3GPP standards. Validation is conducted using two distinct methods: an OAI-RF simulator-based setup for controlled testing and an O-RAN-based Localization Testbed at EURECOM in real-world conditions. The results demonstrate the viability of this open-source UL-TDoA implementation, enabling precise positioning in various environments. By making this implementation publicly available, the study paves the way for widespread research, development, and innovation in the field of 5G positioning technologies, fostering collaboration and accelerating the advancement of cellular network positioning.
Paper Structure (19 sections, 8 equations, 18 figures, 2 tables)

This paper contains 19 sections, 8 equations, 18 figures, 2 tables.

Table of Contents

  1. Introduction
  2. 3GPP's framework for UL-TDOA based positioning
  3. Protocol Required for UL-TDoA Positioning Method in OAI
  4. Contribution to the OAI and Implementation Status of UL-TDoA
  5. UL-TDoA Positioning Procedure in OAI
  6. Enabling ToA estimation in OAI's gNB
  7. gNB-PHY
  8. FAPI interface
  9. gNB-MAC
  10. Validation of our Open-Source UL-TDoA positioning
  11. OAI-rfsimulator based setup
  12. Preparing the Setup
  13. O-RAN based Localization Testbed at EURECOM
  14. Deployment
  15. Logical Architecture
  16. ...and 4 more sections

Figures (18)

  • Figure 1: UE Positioning Architecture applicable to NG-RAN 3gpp_TS38305
  • Figure 2: UL-TDoA Positioning Procedure (3GPP) 3gpp_TS38305.
  • Figure 3: Protocol Layering for LMF to NG-RAN Signalling 3gpp_TS38305
  • Figure 4: End-to-End Implementation of UL-TDoA Positioning Procedure in OAI.
  • Figure 5: Determine Location Request lmf
  • ...and 13 more figures