| Summary: | 碩士 === 國立中央大學 === 資訊工程研究所 === 96 === In this thesis, we propose a new density control algorithm for wireless sensor networks to keep as few as possible sensors in active state to achieve a connected coverage of a specific area of interest. Inactive sensors can turn off sensor modules to save energy for prolonging the network lifetime. Unlike other algorithms, the proposed algorithm does not rely on position information of sensors. It just requires each active sensor to send two beacons of distinct transmission ranges periodically. Sensors can then decide to stay in the active state or inactive state. When any active sensor runs out of energy or fails, one or more inactive sensors can switch to the active state to take over the surveillance responsibility. The proposed algorithm is thus of the capability of fault-tolerance. Under the assumption of sufficiently high density of sensors and the assumption of Rc > 2Rs, we show our algorithm can achieve optimal connected coverage in the best case, where Rc and Rs are the radio communication radius and the sensing radius of sensors, respectively. Furthermore, we perform simulation experiments to investigate the impact of the node density and the ratio a on algorithm performance, where a, (1/√3) < a < 1, is the ratio of the transmission ranges of the two beacons. By simulation results, we can set a to be proper values according to given node densities for better performance.
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