Extending lifetime of sensor network by introducing mobile nodes and its evaluation using real devices

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In this study, we proposed a method for maximizing the lifetime of a wireless sensor network which k-covers the target field, by making minimum number of nodes operate and putting other nodes in sleep. For this objective, we first formulated the problem to decide the operating mode for each sensor node and the multi-hop communication route at each time to maximize the k-coverage time. This problem is a typical combinatorial optimization problem, and thus it is hard to find the optimal solution for practical time. So, we proposed a method which periodically finds the solution for each of shorter time periods, which are made by subdividing the entire time period. We proposed two methods; the first one is to choose active nodes in order of their contribution degree to the field k-coverage, and the second one is to find layers that each of them 1-covers the field, and choose k active layers for k-coverage. The second method is considered to be more fault-tolerant. In order to evaluate the effectiveness of our algorithms in terms of k-coverage time, we compared our methods with methods in which some of the proposed features are disabled. Through simulation-based comparison, we confirmed that the proposed methods achieve 1.1 to 1.7 times longer lifetime regardless of k and the number of nodes, than the other methods.