| Summary: | 碩士 === 國立中興大學 === 資訊科學與工程學系所 === 97 === In recent years, the advancement in wireless communications and electronics has enabled the development of wireless sensor networks. The main applications of wireless sensor networks include battlefield surveillance, environmental monitoring, health-care system, and animal tracking etc. In general, a wireless sensor network is composed of a large number of low-cost sensors that are densely deployed in a remote or hostile region. When the sensors run out of energy, it is hard or impossible to recharge the battery power of all sensors. As a result, power-saving is a critical research issue in wireless sensor networks.
In this thesis, our research focuses on the target coverage problem in wireless sensor networks with variable sensing range. In [1, 2], Cardei considered deploying a large number of sensors to cover a set of targets with known locations in a specific area, and tried to divide the sensors into maximum different set covers, each of which can completely cover all targets. Then each set cover can work in turn to extend the network lifetime. Cardei defined this problem as Maximum Set Covers problem , and he proposed a Greedy-MSC heuristic algorithm to solve it [2]. Extending the Greedy-MSC heuristic, we design two energy-efficient algorithms with variable sensing range: Homogeneous-SRD and Heterogeneous-SRD. They can minimize the sensing range of every sensor in the active set cover while the sensing objective is met. By decreasing sensing range, we can save more power in a wireless sensor network.
Our simulation results show that compared with Greedy-MSC heuristic, Homogeneous-SRD can effectively extend the network lifetime. Based on our proposed mathematical model, we compute the power saving rates of Homogeneous -SRD and Heterogeneous-SRD. We find that Heterogeneous-SRD can save power twice as much as Homogeneous-SRD can save.
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