Clock Synchronization and Localization of Nodes in Wireless Sensor Network

Abstract

Wireless sensor networks (WSNs) connect many sensor nodes that are spatially newlinedistributed in the field of interest. In this research, we concentrate on two newlinerequirements of WSN, namely, clock synchronization of the nodes and localization newline(finding the position) of the nodes. In this research, we have proposed separate novel newlinemethods to solve these two problems, as well as a combined method to synchronize newlineand localize the nodes simultaneously. newlineThe first work proposes the Clock Synchronization by Least Common Multiple newline(CSLCM) method to remove the clock offset and clock skew among the sensor nodes. newlineThe proposed CSLCM enables the nodes to reach a network synchronization time by newlinecalculating the least common multiple of their Clock Time Period (CTP). The network newlineis organized into clusters and every node reaches the network synchronization time newlineusing its own CTP. Simulation results show that, the CSLCM algorithm is more newlineefficient compared to the Average Time Synchronization with Pairwise messages newline(ATSP) in terms of accuracy, communication overhead and computation overhead. newlineSecondly, we propose a localization technique based on Bilateration and newlineComparison Localization (BACL) for dense networks, which considers two reference newlinenodes to determine the unknown position of a third node. The mirror positions newlineresulted from bilateration are resolved by comparing their coordinates with the newlinecoordinates of the reference nodes. Additionally, we use network clustering to further newlinerefine the location of the nodes. We show that BACL has several advantages over newlineEnergy Aware Co- operative Localization (EACL) and Underwater Recursive Position newlineEstimation (URPE): (1) BACL uses bilateration (needs only two reference nodes) newlineinstead of trilateration (that needs three reference nodes), (2) BACL needs reference newline(anchor) nodes only on the field periphery, and (3) BACL needs substantially less newlinecommunication and computation. We also explore the BACL localization error when newlinethe anchor nodes are placed on one or multiple sides of a rectangular field, as a t