Estimation of clock parameters and performance benchmarks for synchronization in wireless sensor networks

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Title: Estimation of clock parameters and performance benchmarks for synchronization in wireless sensor networks
Author: Chaudhari, Qasim Mahmood
Abstract: Recent years have seen a tremendous growth in the development of small sensing devices capable of data processing and wireless communication through their embed - ded processors and radios . Wireless Sensor Networks (WSNs ) are ad hoc networks consisting of such devices gaining importance due to their emerging applications . For a meaningful processing of the information sensed by WSN nodes , the clocks of these individual nodes need to be matched through some well de ?ned procedures . This dissertation focuses on deriving e ?cient estimators for the clock parameters of the network nodes for synchronization with the reference node and the estimators variance thresholds are obtained to lower bound the maximum achievable performance . For any general time synchronization protocol involving a two way message ex - change mechanism , the BLUE -OS and the MVUE of the clock o ?set between them is derived assuming both symmetric and asymmetric exponential network delays . Next , with the inclusion of clock skew in the model , the joint MLE of clock o ?set and skew under both the Gaussian and the exponential delay model and the corresponding al - gorithms for ?nding these estimates are presented . Also , for applications where even clock skew correction cannot maintain long -term clock synchronization , a closed -form expression for the joint MLE for a quadratic model is obtained . Although the derived MLEs are not computationally very complex , two compu - tationally e ?cient algorithms have been proposed to estimate the clock o ?set and skew regardless of the distribution of the delays . Afterwards , extending the idea of having inactive nodes in a WSN overhear the two -way timing message communication between two active (master and slave ) nodes , the MLE , the BLUE -OS , the MVUE and the MMSE estimators for the clock o ?sets of the inactive nodes located within the communication range of the active nodes are derived , hence synchronizing with the reference node at a reduced cost . Finally , focusing on the the one -way timing exchange mechanism , the joint MLE for clock phase o ?set and skew under exponential noise model and the Gibbs Sampler for a receiver -receiver protocol is formulated and found via a direct algorithm . Lower and upper bounds for the MSE of JMLE and Gibbs Sampler are introduced in terms of the MSEs of the MVUE and the conventional BLUE , respectively .
URI: http : / /hdl .handle .net /1969 .1 /ETD -TAMU -2945
Date: 2009-05-15

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Estimation of clock parameters and performance benchmarks for synchronization in wireless sensor networks. Available electronically from http : / /hdl .handle .net /1969 .1 /ETD -TAMU -2945 .

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