A software-defined radio implementation of timestamp-free network synchronization

This paper describes a real-time implementation of timestamp-free network synchronization using RF signaling between a master and slave node. Rather than conventional approaches of exchanging digital timestamps through a dedicated synchronization protocol, timestamp-free synchronization is performed implicitly at the physical layer through timing of a master node's responses to a slave node. This approach was implemented in C++ on a pair of Ettus USRP E310 software defined radios, and extends a previous implementation at audio frequencies using acoustic hardware. Experimental results using modulated sinc pulses demonstrate synchronization accuracy less than 12% of the sampling period. The results confirm previous theoretical studies suggesting that the timestamp-free synchronization approach accurately accounts for propagation delay, frequency offset, and stochastic drift.