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A hybrid optical–wireless network for decimetre-level terrestrial positioning


Global navigation satellite systems (GNSS) are widely used for navigation and time distribution1,2,3, features that are indispensable for critical infrastructure such as mobile communication networks, as well as emerging technologies such as automated driving and sustainable energy grids3,4. Although GNSS can provide centimetre-level precision, GNSS receivers are prone to many-metre errors owing to multipath propagation and an obstructed view of the sky, which occur particularly in urban areas where accurate positioning is most needed1,5,6. Moreover, the vulnerabilities of GNSS, combined with the lack of a back-up system, pose a severe risk to GNSS-dependent technologies7. Here we demonstrate a terrestrial positioning system that is independent of GNSS and offers superior performance through a constellation of radio transmitters, connected and time-synchronized at the subnanosecond level through a fibre-optic Ethernet network8. Using optical and wireless transmission schemes similar to those encountered in mobile communication networks, and exploiting spectrally efficient virtual wideband signals, the detrimental effects of multipath propagation are mitigated9, thus enabling robust decimetre-level positioning and subnanosecond timing in a multipath-prone outdoor environment. This work provides a glimpse of a future in which telecommunication networks provide not only connectivity but also GNSS-independent timing and positioning services with unprecedented accuracy and reliability.

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Fig. 1: TNPS testbed.
Fig. 2: PNT radio signal structure.
Fig. 3: Positioning performance.
Fig. 4: Multipath and timing performance.

Data availability

The datasets that support this paper are available at

Code availability

The code to process the datasets that support this paper is available under the MIT-0 License at


  1. Enge, P. K. The Global Positioning System: signals, measurements, and performance. Int. J. Wirel. Inf. Netw. 1, 83–105 (1994).

    Article  Google Scholar 

  2. Allan, D. W. & Weiss, M. A. Accurate time and frequency transfer during common-view of a GPS satellite. In Proc. 34th Annual Frequency Control Symposium, USAERADCOM 334–346 (IEEE, 1980).

  3. European GNSS Agency GNSS Technology Report, Issue 3 (Publications Office of the European Union, 2020);

  4. Muljadi, E. et al. Synchrophasor Applications for Wind Power Generation Technical Report (US National Renewable Energy Laboratory, 2014);

  5. Li, T., Zhang, H., Gao, Z., Chen, Q. & Niu, X. High-accuracy positioning in urban environments using single-frequency multi-GNSS RTK/MEMS-IMU integration. Remote Sens. 10, 205 (2018).

    Article  ADS  Google Scholar 

  6. Humphreys, T. E., Murrian, M. J. & Narula, L. Deep-urban unaided precise global navigation satellite system vehicle positioning. IEEE Intell. Transp. Syst. Mag. 12, 109–122 (2020).

    Article  Google Scholar 

  7. Sadlier, G., Flytkjær, R., Sabri, F. & Herr, D. The Economic Impact on the UK of a Disruption to GNSS (London Economic, 2017).

  8. Serrano, J. et al. The White Rabbit project. In Proc. 12th International Conference on Accelerator and Large Experimental Physics Control Systems (ICALEPCS) 93–95 (JACoW, 2009).

  9. Dun, H., Tiberius, C. C. J. M., Janssen, G. J. M. & Diouf, C. E. V. Time delay estimation based on multi-band multi-carrier signal in multipath environments. In Proc. 32nd International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2019) 2299–2313 (ION, 2019).

  10. Braasch, M. S. in Springer Handbook of Global Navigation Satellite Systems (eds Teunissen, P. J. & Montenbruck, O.) 443–468 (Springer, 2017).

  11. Buttler, W. T. et al. Practical free-space quantum key distribution over 1 km. Phys. Rev. Lett. 81, 3283–3286 (1998).

    Article  ADS  CAS  Google Scholar 

  12. US National Timing Resilience and Security Act of 2017 (Library of Congress, 2017);

  13. Alternative Position, Navigation and Timing (PNT) Services: Tender Specifications Call for Tenders DEFIS/2020/OP/0007 (European Commission, 2020);

  14. Hansen, A. et al. Complementary PNT and GPS Backup Technologies Demonstration Report: Sections 1 through 10 Report number DOT-VNTSC-20-07 (John A. Volpe National Transportation Systems Center (U.S.), 2021);

  15. Benzerrouk, H. et al. Alternative PNT based on iridium next LEO satellites Doppler/INS integrated navigation system. In 2019 26th Saint Petersburg International Conference on Integrated Navigation Systems (ICINS) 1–10 (IEEE, 2019).

  16. Cheong, J. W., Wei, X., Politi, N., Dempster, A. G. & Rizos, C. Characterising the signal structure of Locata’s pseudolite-based positioning system. In International Global Navigation Satellite Systems Society IGNSS Symposium 2009 1–3 (IGNSS, 2009).

  17. Rizos, C. & Yang, L. Background and recent advances in the Locata terrestrial positioning and timing technology. Sensors 19, 1821 (2019).

    Article  ADS  PubMed Central  Google Scholar 

  18. Yavari, M. & Nickerson, B. G. Ultra-wideband Wireless Positioning Systems Technical Report TR14-230 (Faculty of Computer Science, Univ. New Brunswick, 2014).

  19. Alarifi, A. et al. Ultra wideband indoor positioning technologies: analysis and recent advances. Sensors 16, 707 (2016).

    Article  ADS  PubMed Central  Google Scholar 

  20. Prager, S., Haynes, M. S. & Moghaddam, M. Wireless subnanosecond RF synchronization for distributed ultrawideband software-defined radar networks. IEEE Trans. Microw. Theory Tech. 68, 4787–4804 (2020).

    Article  ADS  Google Scholar 

  21. Razavi, S. M. et al. Positioning in cellular networks: past, present, future. In 2018 IEEE Wireless Communications and Networking Conference (WCNC) 1–6 (IEEE, 2018).

  22. Dun, H., Tiberius, C. C. J. M., Diouf, C. & Janssen, G. J. M. Design of sparse multiband signal for precise positioning with joint low-complexity time delay and carrier phase estimation. IEEE Trans. Veh. Technol. 70, 3552–3567 (2021).

    Article  Google Scholar 

  23. Progri, I. F., Bromberg, M. C. & Michalson, W. R. Maximum-likelihood GPS parameter estimation. NAVIGATION 52, 229–238 (2005).

    Article  Google Scholar 

  24. Guvenc, I. & Chong, C.-C. A survey on TOA based wireless localization and NLOS mitigation techniques. IEEE Commun. Surv. Tutor. 11, 107–124 (2009).

    Article  Google Scholar 

  25. Yan, J., Tiberius, C. C. J. M., Bellusci, G. & Janssen, G. J. M. Non-line-of-sight identification for indoor positioning using ultra-wideband radio signals. NAVIGATION 60, 97–111 (2013).

    Article  Google Scholar 

  26. Riley, W. J. Handbook of Frequency Stability Analysis NIST Special Publication 1065 (NIST, 2008).

  27. Śliwczyński, Ł., Krehlik, P., Czubla, A., Buczek, Ł. & Lipiński, M. Dissemination of time and RF frequency via a stabilized fibre optic link over a distance of 420 km. Metrologia 50, 133 (2013).

    Article  ADS  Google Scholar 

  28. Sotiropoulos, N., Okonkwo, C. M., Nuijts, R., De Waardt, H. & Koelemeij, J. C. J. Delivering 10 Gb/s optical data with picosecond timing uncertainty over 75 km distance. Opt. Express 21, 32643–32654 (2013).

    Article  ADS  CAS  PubMed  Google Scholar 

  29. Daniluk, G. White Rabbit Calibration Procedure, Version 1.1 CERN BE-CO-HT (Open Hardware Repository, 2015);

  30. Lipiński, M. et al. White Rabbit applications and enhancements. In 2018 IEEE International Symposium on Precision Clock Synchronization for Measurement, Control, and Communication (ISPCS) 1–7 (IEEE, 2018).

  31. Boven, P., van Tour, C. & Smets, R. Demonstration of VLBI Synchronization via Existing SURFnet/LOFAR Network ASTERICS GA Deliverable D5.14 (ASTERICS collaboration, 2019);

  32. Lombardi, M. A. Evaluating the frequency and time uncertainty of GPS disciplined oscillators and clocks. Meas. J. Meas. Sci. 11, 30–44 (2016).

    Google Scholar 

  33. Girela-López, F. et al. IEEE 1588 high accuracy default profile: applications and challenges. IEEE Access 8, 45211–45220 (2020).

    Article  Google Scholar 

  34. Dierikx, E. F. et al. White Rabbit precision time protocol on long distance fiber links. IEEE Trans. Ultrason. Ferroelectr. Freq. Control 63, 945–952 (2016).

    Article  PubMed  Google Scholar 

  35. Yang, M. et al. iLPS: local positioning system with simultaneous localization and wireless communication. In IEEE INFOCOM 2019-IEEE Conference on Computer Communications 379–387 (IEEE, 2019).

  36. White Rabbit ZEN TP-FL. Orolia (2022).

  37. USRP X310 high performance software defined radio. Ettus (2019).

  38. Diouf, C., Dun, H., Kazaz, T., Janssen, G. & Tiberius, C. Demonstration of a decimeter-level accurate hybrid optical–wireless terrestrial positioning system. In Proc. 33rd International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2020) 2220–2228 (ION, 2020).

  39. Li, Y. G. & Stuber, G. L. Orthogonal Frequency Division Multiplexing for Wireless Communications (Springer, 2006).

  40. Yan, J., Tiberius, C. C. J. M., Teunissen, P. J. G., Bellusci, G. & Janssen, G. J. M. A framework for low complexity least-squares localization with high accuracy. IEEE Trans. Signal Process. 58, 4836–4847 (2010).

    Article  ADS  MathSciNet  MATH  Google Scholar 

  41. Teunissen, P. J. G. The least-squares ambiguity decorrelation adjustment: a method for fast GPS integer ambiguity estimation. J. Geod. 70, 65–82 (1995).

    Article  ADS  Google Scholar 

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This research is funded through the Dutch Research Council (NWO) under grants 12346 and 13970, with additional support from KPN, VSL, OPNT and Fugro. We acknowledge support from L. Boonstra, T. Theijn and R. Smets on the optical infrastructure, from L. Colussi and F. van Osselen on obtaining the 3.96-GHz experimental license, and R. Tamboer and T. Jonathan on realizing the testbed at TGV.

Author information

Authors and Affiliations



Conceptualization, J.C.J.K., G.J.M.J. and C.C.J.M.T.; methodology, J.C.J.K., H.D., C.E.V.D., E.F.D., G.J.M.J. and C.C.J.M.T.; prototype system development, H.D. and C.E.V.D.; prototype deployment and field trial (experiment), H.D, C.E.V.D., E.F.D., G.J.M.J. and C.C.J.M.T.; measurement data processing, analysis and validation, H.D. and C.E.V.D.; writing—original draft preparation, J.C.J.K.; writing—review and editing, J.C.J.K., H.D., C.E.V.D., E.F.D., G.J.M.J. and C.C.J.M.T.; visualization, J.C.J.K., H.D. and C.E.V.D.; project administration and funding acquisition, J.C.J.K., G.J.M.J. and C.C.J.M.T. All authors have read and agreed to the published version of the manuscript.

Corresponding author

Correspondence to Christian C. J. M. Tiberius.

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Competing interests

J.C.J.K. is co-founder and shareholder of OPNT bv. The other authors declare no competing interests.

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Nature thanks Todd Humphreys, Christos Laoudias and the other, anonymous, reviewer(s) for their contribution to the peer review of this work. Peer reviewer reports are available.

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Extended data figures and tables

Extended Data Fig. 1 Map of the TNPS testbed.

Locations of data centres at Delft University of Technology (TU D) and schematic representation of the fibre-optic connections are shown. The reference atomic clocks that are used to realize UTC(VSL) and synchronize the WR network are located at VSL. Map data copyright OpenStreetMap (, obtained under Open Database License 1.0.

Extended Data Fig. 2 Car set-up and TGV site.

The Rx antenna and two 360° prisms are mounted onto the roof of a car. In the background part of the TGV test site is visible (viewing direction is south east). The various Tx-i antennas are indicated, as well as the two total stations. Tx-2 is hidden from the view by tree branches.

Extended Data Fig. 3 Comparison of positioning results in synchronous and asynchronous mode.

a, Ground-truth trajectories of two different runs, one with the Rx USRP operated in synchronous mode (blue), and one with the Rx USRP in asynchronous mode (yellow). b, TD position errors and 95% ellipses for the synchronous and asynchronous runs shown in a, following the same colour coding. The black cross indicates the GT solution and its uncertainty. c, Same as in b, but for CP ambiguity-float solutions. Note the different scale of the graph. d, Same as in b, but for CP ambiguity-fixed solutions. During the early stages of the run in synchronous mode (blue), an incorrect integer correction was applied, leading to small islands of biased position errors.

Extended Data Fig. 4 Horizontal precision and constellation size.

Horizontal positioning precision, (σEast2 + σNorth2)1/2, with σEast and σNorth the position standard deviations as determined from a nonlinear least-squares optimization that assumes ranging errors with a standard deviation of σr = 6 cm for all transmitters. Values above 50 cm are clipped and replaced by white areas. Shown also are OFDM-TD position solutions for the run with the asynchronous receiver of Extended Data Fig. 3 (blue curves), and the corresponding ground-truth path (red curves). a, Precision and position solutions for the full TNPS constellation. b, Precision and position solutions for the TNPS constellation with Tx-1 and Tx-3 removed. c, Precision and position solutions for the TNPS constellation with Tx-1, Tx-2, and Tx-5 removed. d, Precision and position solutions for the TNPS constellation with Tx-6 removed.

Extended Data Fig. 5 Modified Allan deviation.

Modified Allan deviation measured between WR-GM and WR-SL at VSL (Fig. 1b) after a round trip through 8.2 km of installed optical fibre.

Extended Data Table 1 TD positioning RMSE for various reduced constellations
Extended Data Table 2 CP positioning RMSE for various reduced constellations

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Koelemeij, J.C.J., Dun, H., Diouf, C.E.V. et al. A hybrid optical–wireless network for decimetre-level terrestrial positioning. Nature 611, 473–478 (2022).

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