Time synchronization with delay estimation and joint clock skew and offset estimation for UAV networks

Timing synchronization usually is a key element of Unmanned Aerial Vehicle (UAV) networks and is the basis for emerging applications like Wireless Time Sensitive Networking (WTSN). Achieving high precision time synchronization on the order of a few to tens of nanoseconds can be a challenge in wireless networks in general and flying wireless networks in specific. This paper seeks to tackle this issue by tracking the relative delays between UAV nodes with Kalman filter and on top of that jointly estimating the clock skew and offset. The Kalman filter based relative delay estimator is first derived. Then the joint clock offset and skew estimator which is based on the recursive least squares (RLSE) method is derived. Finally, the Cramer-Rao lower bound (CRLB) of the joint clock offset and skew estimator is derived. Numerical results show that the method proposed by this work is effective and necessary in flying wireless networks.