Relay node placement in structurally damaged wireless sensor networks via triangular steiner tree approximation

Wireless sensor networks (WSNs) have many applications which operate in hostile environments. Due to the harsh surroundings, WSNs may suffer from a large scale damage that causes many nodes to fail simultaneously and the network to get partitioned into multiple disjoint segments. In such a case, restoring the network connectivity is very important in order to avoid negative effects on the applications. In this paper, we pursue the placement of the least number of relay nodes to re-establish a strongly connected network topology. The problem of finding the minimum count and the position of relay nodes is NP-hard and hence we pursue heuristics. We present a novel three-step algorithm called FeSTA which is based on steinerizing appropriate triangles. Each segment is represented by a terminal. Each subset of 3 terminals forms a triangle. Finding the optimal solution for a triangle (i.e. connecting 3 segments) is a relatively easier problem. In the first step, FeSTA finds the best triangles and form islands of segments by establishing intra-triangle connectivity. Then in the second, disjoint islands of segment are federated. In the final step, the steinerized edges are optimized. The performance of FeSTA is validated through simulation.