A NOVEL COVERAGE AND CONNECTIVITY PRESERVING ROUTING PROTOCOL FOR MISSION-CRITICAL WIRELESS SENSOR NETWORKS

摘要

Mission-critical wireless sensor networks (WSNs) have been found to be very useful for many military and civil applications such as disaster management, surveillance of battle fields and e-healthcare. Coverage preservation and connectivity are the most essential functions to guarantee quality of service (QoS) in mission-critical WSNs. By optimizing coverage, the deployment strategy would guarantee that optimum area in the sensing field is covered by sensors, as required by various types of mission-critical applications. Whereas by ensuring that the network is connected, it is ensured that the sensed information is transmitted to other nodes and possibly to a centralized base station which makes valuable decisions for the applications. However, a trade-off exists between sensing coverage and network lifetime due to the limited energy supplies of sensor nodes. In this paper, we propose a Coverage and Connectivity Preserving Routing Protocol for mission-critical WSNs (CCPRP) to accommodate connectivity, energy-balance and coverage-preservation for sensor nodes in WSNs that are hierarchically clustered. The energy consumption for radio transmissions and the residual energy over the network are taken into account when the proposed protocol determines an energy-efficient route for a data from elected cluster head to the base station through elected gateway. We define a cost metric to favour nodes with high energy-redundantly covered as better candidates for cluster heads in a way to improve the performance of sensing coverage, reduce communications energy and prolonging the effective network lifetime with optimal data delivery. Furthermore, we propose a novel area coverage protocol called CCPRP-AC for scheduling the sensing activity of sensor nodes that are deployed to sense point-targets in WSN using information coverage. The simulation results demonstrate that the proposed protocol CCPRP is able to increase the duration of the on-duty network and provide up to 124 76% of extra service time with 100% sensing coverage ratio comparing with other existing protocols, and the protocol CCPRP-AC achieves k-coverage of a field, where every point is covered by at least k sensors with a minimum number of sensors.