Recently directional sensors have been widely deployed as they are more practicable under constraints of manufacture, size and cost. One common functionality of networks formed by such directional sensors is to monitor a set of discrete targets continuously. Large scale deployment makes sensor recharge impossible. By abundant deployment, it is reasonable and necessary to select subsets of sensors to operate alternatively so as to prolong the network lifetime. Such problem has been proved to be NP-Complete. This paper approximates network lifetime problem by randomized algorithm. Through constructing elementary sessions, which denotes active subset of sensors covering all targets, and linear programming, the approximating solution is derived within extremely less duration comparing to previous works. Simulation results demonstrate the algorithm’s performance and sound explanation is also presented.
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