Clock estimation for long-term synchronization in wireless sensor networks with exponential delays

Abstract

Although the existing time synchronization protocols in wireless sensor networks (WSNs) areefficient for short periods, many applications require long-term synchronization among the nodes, forexample, coordinated sleep and wakeup modes, and synchronized sampling. In such applications, experimentshave shown that even clock skew correction cannot maintain long-term clock synchronization anda quadratic model of clock variations can better capture the dynamics of the actual clock model involved,hence increasing the resynchronization period and conserving significant energy. This paper derives themaximum likelihood (ML) estimator for all the clock parameters in a two-way timing exchange modelwith exponential delays. The same estimation procedure can be applied to one-way timing exchangemodels with little modification.