Maximizing the Lifetime of a Barrier of Wireless Sensors

To make a network last beyond the lifetime of an individual sensor node, redundant nodes must be deployed. What sleep-wake-up schedule can then be used for individual nodes so that the redundancy is appropriately exploited to maximize the network lifetime? We develop optimal solutions to both problems for the case when wireless sensor nodes are deployed to form an impenetrable barrier for detecting movements. In addition to being provably optimal, our algorithms work for nondisk sensing regions and heterogeneous sensing regions. Further, we provide an optimal solution for the more difficult case when the lifetimes of individual nodes are not equal. Developing optimal algorithms for both homogeneous and heterogeneous lifetimes allows us to obtain, by simulation, several interesting results. We show that even when an optimal number of sensor nodes has been deployed randomly, statistical redundancy can be exploited to extend the network lifetime by up to seven times. We also use simulation to show that the assumption of homogeneous lifetime can result in severe loss (two-thirds) of the network lifetime. Although these results are specifically for barrier coverage, they provide an indication of behavior for other coverage models.