Estimation of Clock Offsets and Skews in Wireless Sensor Networks Using Three-Way Message Exchange

Abstract

Performance of a wireless sensor network (WSN) depends on synchronism of clocksat sensor nodes. These clocks need to be synchronized for a network-wide, common time reference. Existingapproachesto WSN synchronizationignore time-stampsthat wereexchanged during the synchronization process,leading undesirably to estimation errors in clock offsets and skews. This paper proposes an accurate method, called three-way message exchange,to estimate clock offsets and skews using maximum likelihood estimation, where transmission and processing delayshavea Gaussian distribution.In this method, each node sends and receives time-stamps to and from the other nodes, thereby improving timing accuracy of all nodes in the network.Performance of the proposed method is evaluated through simulation of biases.Three-way message exchange is found to be accurate and achievenegligibly smallbiases, confirming its practical applications to WSNs.