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. Our 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. We show that the proposed algorithm is more robust than the previous algorithms in this area and outperforms all of them. The simulation results verify the effectiveness of the proposed algorithm in calculating the median in a distributed scheme and in detecting the defective nodes in the network.