High-Precision Wireless Clock Synchronization for Distributed Wireless Networks: A Comparative Study using Software Defined Radios

Abstract:
Clock synchronization is a critical enabler for distributed wireless communication and radar systems. This paper presents an all-digital implementation and experimental comparison of two over-the-air clock synchronization methods using software-defined radios (SDRs). The methods use single- and twotone transmissions and proceed via two key steps: (1) a master node broadcasting reference tones, and (2) slave nodes estimating and compensating for their clock offsets using a digital frequency translator and an arbitrary resampler. Experimental results demonstrate that the single-tone method achieves significantly higher precision, with a clock offset standard deviation of 1.64 parts per billion (ppb), outperforming the two-tone method (74.3 ppb). Analytical expressions, supported by Monte-Carlo simulations, further validate these findings, revealing that the singletone approach offers two orders of magnitude better accuracy in static environments. Furthermore, the analytical results also decouple and quantify the errors due to uncompensated Doppler shifts, revealing that neither method holds an advantage in mobile scenarios, where Doppler effects degrade performance. Based on these results, we recommend the single-tone method for alldigital, over-the-air synchronization in distributed networks. To support reproducibility, we provide an open-source C implementation of a Lagrange interpolator-based resampler.