Optimized relay node placement for connecting disjoint wireless sensor networks

Wireless sensor networks (WSNs) often operate in a harsh environment such as battlefield and may suffer simultaneous failure of multiple sensors that cause the network to become partitioned into disjoint segments. In order to prevent the application from being inoperative, restoring the overall network connectivity is crucial. In this paper, we propose an effective strategy for establishing connectivity among the partitioned segments by deploying the least count of relay nodes (RNs). Finding the optimal number and position of RNs is NP-hard and we thus pursue heuristics. We propose an Optimized Relay node placement algorithm using a minimum Steiner tree on the Convex hull (ORC). ORC strives to identify Steiner points (SPs) in which relays are populated such that the segments will be connected with the least number of relays. ORC deploys RNs inwards from the periphery of the area identified by the convex hull. We analyze ORC mathematically and explain the beneficial aspects of the resulting topology with respect to connectivity, and traffic balance. The performance of ORC is validated through extensive simulation experiments.