EQAR: Effective QoS-Aware Relay Node Placement Algorithm for Connecting Disjoint Wireless Sensor Subnetworks

In some applications of wireless sensor networks (WSNs), it may be necessary to link a number of disjoint segments in order to form a federated system. The segments can be simply distinct WSNs that operate autonomously or partitions of a single WSN that has suffered significant damage. Linking these segments may be subject to different intersegment quality of service (QoS) requirements. This paper presents an effective approach for federating these segments by populating the least number of relay nodes (RNs) such that the connectivity and QoS requirements are satisfied. Finding the optimal number and position of RNs is NP-hard and heuristics are thus pursued. The deployment area is modeled as a grid with equal-sized cells. A cost is assigned to each cell based on the residual capabilities of relays populated in it. The optimization problem is then mapped to finding the cell-based least-cost paths that collectively meet the QoS requirements. The performance of our approach is validated through extensive simulation experiments. We further demonstrate the beneficial aspects of the resulting topology with respect to degree of connectivity and fault resilience.