Low-Cost Pseudolites: A Loop-Back Time Synchronization Scheme for Pseudolites Using Real-Time Clock Offset Calibration for Reliable PNT

Muhammad Subhan Hameed, Mathias Philips-Blum, Thomas Pany, Daniel Sanroma, and Sowmyashree Lakshmaiah

Abstract: This paper presents the development of a cost-effective pseudolite (PL) transmitter assembly capable of transmitting a GNSS-like signal for navigation. A novel loop-back time synchronization scheme is introduced, which utilizes PL pseudorange observations over a predefined cable length to achieve real-time clock offset calibration, ensuring reliable position, velocity and time (PVT) solutions. The paper details the PL signal design, transmitter hardware implementation and the loop-back time synchronization framework providing validation results using a GNSS signal simulator over pre-defined cable lengths with a RMSE within 1 m. Moreover, single point positioning (SPP) results are presented for measurement scenarios using both GNSS-only and GNSS combined with the PL signal in terms of positioning accuracy and dilution-of-precision (DOP) metrics. The combined use of the PL signal with GPS shows an overall improvement in DOP metrics and a reduction in vertical position error by approximately 3 meters. Overall, the presented transmitter architecture eliminates the need for expensive synchronization hardware and complex timing protocols and lays foundation for easily deployable ground-based PL transmitters.
Published in: Proceedings of the 37th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2024)
September 16 - 20, 2024
Hilton Baltimore Inner Harbor
Baltimore, Maryland
Pages: 1444 - 1460
Cite this article: Hameed, Muhammad Subhan, Philips-Blum, Mathias, Pany, Thomas, Sanroma, Daniel, Lakshmaiah, Sowmyashree, "Low-Cost Pseudolites: A Loop-Back Time Synchronization Scheme for Pseudolites Using Real-Time Clock Offset Calibration for Reliable PNT," Proceedings of the 37th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2024), Baltimore, Maryland, September 2024, pp. 1444-1460. https://doi.org/10.33012/2024.19725
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