Greedy Geographic Routing is Good Enough in Sensing Covered Networks

This paper presents a theoretical analysis of greedy geographic routing protocols on a common class of wireless sensor networks that must provide sensing coverage over a geographic area. Contrary to well known results on random networks, we prove that the Greedy Geographic Forwarding and our new greedy protocol always succeed in any sensing covered network when the communication range is at least twice the sensing range. Furthermore, we derive the analytic upper bound for the network dilation of sensing covered networks and quantify its relationship with the ratio between communication range and sensing range. Simulations show that, when the ratio between communication range and sensing range reaches 4.5, the studied greedy routing protocols can find network paths whose hop count on a sensing covered network approaches 1.5 times that of an ideal network. These results provide several important insights into the design of sensor networks. Simple greedy geographic routing protocols are "good enough" in this class of wireless sensor networks, and more sophisticated routing protocols designed to handle routing voids are not necessary. In addition, redundant sensors can be turned off without significant loss in communication performance as long as the remaining active nodes maintain sensing coverage. This result provides a theoretical justification of sensing coverage control protocols that conserve energy through sleep schedules