Minimal Node Placement for Ensuring Target Coverage With Network Connectivity and Fault Tolerance Constraints in Wireless Sensor Networks

Target coverage, connectivity, and fault tolerance are three challenging issues in wireless sensor networks. Target coverage aims to provide a sufficient monitoring quality where all targets in the surveillance region are covered by sensor nodes. Meanwhile, connectivity and fault tolerance seeks to guarantee a satisfactory communication capability where all sensors can connect to base station via relay nodes, while always able to find a backup path in case of failure. In this paper, we focus on minimizing the number of nodes (i.e., sensor nodes and relay nodes) while ensuring target coverage, connectivity and fault tolerance in wireless sensor networks. We approach this problem as two sub-problems. The first is Target Coverage, which requires placing sensor nodes to cover all targets. The second is Network Connectivity and Fault Tolerance, in which relay nodes need to be placed to connect sensor nodes to the base station, along with a backup path in case of failure. We propose an improved formulation of the Fault Tolerance constraint, as well as a new heuristic algorithm, MUTSP, which solves the first phase using a greedy approach, and the second phase with a spanning tree formulation. This method is compared and measured against previous state-of-the-art heuristics for the problem in our experiments. The results show that our algorithm can significantly improve the number of required nodes as well as computation time.