Sleep scheduling for partial coverage in heterogeneous wireless sensor networks

An important issue of research in a dense and random deployment of a wireless sensor network (WSN) is to maintain the coverage of the field and yet minimise the energy consumed by the sensors. Some monitoring applications may require only partial coverage of the field in which case redundant sensors can be identified and scheduled to sleep to minimise the energy consumption. In this paper, we address the problem of determining if a sensor is redundant while the desired partial coverage requirement is met. We assume that the WSN is heterogeneous in which all the sensors may not have the same sensing and/or communication radii. In such a heterogeneous WSN, we use a probabilistic approach to determine the degree of redundancy in the coverage. Given a partial coverage requirement for the field, we propose a scheduling protocol to identify the redundant sensors and put them to sleep. The proposed protocol is fully distributed and does not use any geographical information. We demonstrate the utility of the proposed approach in determining the redundancy in coverage with numerical and simulation results. Our simulations show that the proposed protocol effectively maintains the desired coverage and prolongs the network lifetime.