Fault-Tolerant Implementation of a Distributed MLE-based Time Synchronization Protocol for Wireless Sensor Networks

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IEEE Communications Society
This paper describes the implementation and evaluation of R4Syn protocol on MICAz platform and TinyOS operating system. The contribution is two folds. First, the implementation uses thorough maximum-likelihood estimators (MLE) in the joint offset/skew model, while all similar MLEbased estimators are merely evaluated with theoretical and numerical analysis thus far, and empirical solutions use simple computation estimators, such as offset-only models, or linear regression for skew estimation. Difficulties that has been encountered and overcome are reported in this paper. The second contribution is to consider fault-tolerance, an aspect that has been completely abstracted in previous works. The implementation assures correct behavior despite nodes failure or packet loss, as demonstrated by the experiments. Experimental results also demonstrate microsecond-level precision and long-term validity of the estimators in the joint skew/offset model.
Time Synchronization, Wireless Sensor Networks, Real implementation