Obstacle-Avoiding Connectivity Restoration Based on Quadrilateral Steiner Tree in Disjoint Wireless Sensor Networks

In the harsh environment, wireless sensor networks can suffer from a significant damage that causes many nodes/links to fail simultaneously and the network to get splitted into multiple disjoint partitions. In such case, linking the separated partitions by placing the least number of relay nodes and obstacle-avoiding to re-establish a strongly connected network topology is necessary to maintain the functional operations of wireless sensor network. However, the problem of finding the minimum count and the position of relay nodes is NP-hard hence heuristics methods are preferred. In this paper, we present a novel Obstacle-Avoiding Connectivity Restoration based on Quadrilateral Steiner Tree (OACRQST) algorithm to address this problem. First, the appropriate quadrilaterals are selected to connect the separated partitions and the Steiner nodes of these quadrilaterals are found. Then the disjoint islands are connected with the triangle Steiner tree or minimum spanning tree method, which are not connected by these selected quadrilaterals. Finally, relay nodes are placed to the appropriate position according to the edges of Steiner tree to restore network connectivity. However, if the found position is in the area of the obstacle, the relay node will be placed at the position of the bordering that nearest to the found position. If the network still is not connected, the relay nodes will be placed at the appropriate position according to the bordering of the obstacle starting from the node placed at the position of the bordering nearest to the found position exploring the left rule. Extensive simulation experiments demonstrate the beneficial aspects of the resulting topology with respect to number of relaying nodes, degree of connectivity and fault resilience.