Skew Estimation for Clock Synchronization Without Timestamp Exchange Under Exponential Delays

Clock synchronization is a crucial technique for vehicle networks, which provides the basis for collaborative operations among devices. Accurate synchronization can be achieved by exchanging synchronization packets, but with the expansion of the device scale, frequent interaction of synchronization packets will generate a lot of communication overhead. Recently, an interesting synchronization mechanism, timestamp-free synchronization, has been investigated, which can effectively eliminate the synchronization packets and avoid additional overhead. However, existing research on timestamp-free synchronization is based on the assumption of Gaussian random delays, and the case that random delay following exponential distribution is not considered. Therefore, this article explores the problem of clock parameter estimation with exponential delays based on timestamp-free synchronization. First, the best linear unbiased estimator using order statistics (BLUE-OS) of clock skew for the active node is derived. Then, in the scenario of embedding timestamp-free synchronization into receiver-only synchronization, the BLUE-OS of clock skew for inactive nodes under exponential delays is developed. Simulation results verify the effectiveness of the proposed algorithms and estimators.