Maximizing the Lifetime of a Barrier of Wireless Sensors

To make a network last beyond the lifetime of an individual sensor, redundant sensors must be deployed. What sleep-wakeup schedule can then be used for individual sensors so that the redundancy is appropriately exploited to maximize the network lifetime? We develop optimal solutions to both problems for the case when wireless sensors are deployed to form an impenetrable barrier for detecting movements. In addition to being provably optimal, our algorithms work for non-disk sensing regions and heterogeneous sensing regions. Further, we provide an optimal solution for the more difficult case when the lifetimes of individual sensors 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 sensors have 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.