QoS-aware Relay node Placement for connecting disjoint segments in wireless sensor networks

Wireless sensor networks (WSNs) often operate in severe surroundings and may suffer simultaneous failure of multiple nodes which gets the network partitioned into distinct segments. Restoring connectivity among these segments is crucial in order to prevent the negative effects on the application. This paper investigates effective approaches for recovering from the failure for scenarios where the distance between pairs of segments is longer than twice the communication range of a node and inter-segment quality of service (QoS) requirements have to be met. We model the deployment area as a grid. The optimization problem is then mapped to selecting the fewest cell count to populate relay nodes such that all segments are connected and their QoS requirements are fulfilled. Finding the optimal number and position of relay nodes with respect to length and QoS between segments is NP-hard and heuristics are thus pursued. We present a QoS-aware Relay node Placement (QRP) algorithm and validate the performance of QRP through extensive simulation experiments.