Clock Synchronization for LSTS Algorithm with Random Communication Delays over Wireless Sensor Networks

Abstract

This paper has researched the influence of the probability distribution of all the random bounded communication links delays on the global error of clock synchronization for the least square estimation based time synchronization algorithm (LSTS) over wireless sensor networks (WSNs). First we have presented the large influence of the probability distribution of random bounded communication delays on the global error of clock synchronization under the general condition of communication in WSNs. Then the information of round-trip delays has been introduced to compensate the clock offset in order to decrease the global error of clock synchronization based on the fact that all the round-trip delays between each pair of sensor nodes can be accurately measured. The characteristics of the round-trip delay are analyzed in the case of bidirectional communication between sensor nodes. The clock offset is compensated by the round-trip delay, and the attenuation factor in the consistency theory is introduced. The combined control can greatly decrease the expectation of the global error, the variance of which is also reduced moderately at the same time. Meanwhile the adjusting amplitude of the clock offset also drops sharply. Finally it has shown that the global error of clock skew compensation is mostly determined by the variance rather than the expectation of random communication delays through simulations for the improved algorithm, while the global steady-state error is largely decided by the expectation of random communication delays.