An optimal control approach to clock synchronization

Algorithms following the peer-to-peer Precision Time Protocol (PTP) specified by the IEEE 1588 standard achieve synchronization of distributed clocks by propagating the timing information of a preselected master clock throughout the entire network. Based on this noisy timing information, each slave clock tries to follow as closely as possible the master time. In this work we formulate clock synchronization as a stochastic estimation-control problem. A two dimensional LQG controller is derived which produces an optimal reconstruction of the master time at each slave in the sense of minimizing the mean square error of the estimated master counter and frequency. Owing to its specific structure, the LQG controller does not violate the transparent clock concept. The performance of the proposed controller is verified by simulations.