Validation of Pseudolites with a Loop-Back Time Synchronization Scheme Using a GNSS Signal Simulator

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

Peer Reviewed

Abstract:	This paper presents a test setup to evaluate time synchronization accuracy and its impact on positioning per­formance for pseudolite (PL) systems. The test setup consists of a GNSS signal simulator, providing GNSS signals, for time reference, to a PL system and a rover receiver unit. The PL signal, generated by the PL system, is received by the rover receiver over a cable of known length. The synchronization accuracy is derived by comparing the resolved PL pseudorange at the rover receiver end against the physical cable length. The test setup is validated for a PL system employing a loop-back synchronization scheme. Within this scheme, the PL signal generated by the signal generator is looped back into the PL receiver front­end over a cable of known length, enabling direct pseudorange measurement and leveraging the inherent synchronization of the shared clock source for real-time calibration of the system. The synchronization is evaluated by considering the velocity factors of the transmission cables. It is assessed in terms of the pseudorange RMSE relative to the cable length, which is determined to be less than 1 m. Additionally, the horizontal and vertical position errors are computed, resulting in a RMSE and standard deviation in the order of 0.5 m. Index Terms-pseudolites, time synchronization, calibration.
Published in:	2025 IEEE/ION Position, Location and Navigation Symposium (PLANS) April 28 - 1, 2025 Salt Lake Marriott Downtown at City Creek Salt Lake City, UT
Pages:	466 - 472
Cite this article:	Hameed, Muhammad Subhan, Blum, Mathias Phillip, Pany, Thomas, Sanroma, Daniel, Lakshmaiah, Sowmyashree, "Validation of Pseudolites with a Loop-Back Time Synchronization Scheme Using a GNSS Signal Simulator," 2025 IEEE/ION Position, Location and Navigation Symposium (PLANS), Salt Lake City, UT, April 2025, pp. 466-472.
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