Wireless sensor networks consist of a large number of low-power, limited-processing capability sensors that are deployed in a field to measure physical variables or detect events like intrusion or movement. In surveillance appli- cations, ensuring a high area coverage is an important is- sue requiring a certain number of sensors to be turned on to report events. In this paper, we address the problem of maximizing the sensor network lifetime under area cover- age constraint. For that, we propose a scheduling mecha- nism that calculates, for every time slot of the network op- erating period, an optimal covering subset of sensors that will be activated while all other sensors will go on Sleep. We model this problem as an Integer Linear Programming (ILP) problem, that we resolve using ILOG CPLEX [9] and we show that the obtained solutions provide for a more bal- anced energy consumption when we increase a balancing exponent , which increases network lifetime.
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