Kalman filtering based precision time protocol (PTP) in wireless sensor networks
Xuewu Dai · Caai Transactions on Intelligent Systems · 2012
As a key technique in any distributed system,precision time synchronization plays a core role in time-sensitive industrial wireless networks.Based on the time package exchange techniques,the IEEE 1588 Precision time protocol(PTP) is developed for wired Ethernet and its performance is degraded by the precision of time stamping and jitters of transmission delay.However,in wireless sensor network,it is difficult for the low-cost node to acquire accurate time stamps.Due to the sharing of wireless channel,transmission collision and severe fading,the jitters in WSN are overwhelming.In this paper,the relationship between PTP performance and precision of time stamping in wireless network is investigated.The drifting clock is modeled by an autoregressive(AR) model and the package exchanging behavior of PTP is Abstracted as a set of state space equations.This allows the uncertainties of time stamping and jitters are treated as observation noises,which can be removed by the mature Kalman filter.The simulation results show that the proposed Kalman filtering technique improves the time synchronization,in terms of clock estimation error and clock stability,under various conditions of time stamping uncertainties and jitters.