Detecting the Defective Nodes in Wireless Sensor Networks Using the Nonlinear Consensus of Median

A local algorithm is proposed and analyzed to monitor the health of a wireless sensor network. The authors' previous algorithm, the average consensus-based algorithm, works based on the mean estimator. Therefore, it fails to detect the defective nodes in the presence of large outliers. However, the algorithm proposed in this paper works based on the median estimator, and is able to detect the defective nodes, even in the presence of a large number of outliers. To calculate the median in a distributed scheme, a nonlinear consensus algorithm is proposed. By applying the nonlinear consensus algorithm, all the nodes in the network compute the median iteratively, using only local communications.