| Summary: | 碩士 === 國立中央大學 === 資訊工程研究所 === 94 === In wireless sensor networks, one of the main design challenges is to maintain the connectivity and coverage among nodes in a post deployment scenario. Either the coverage or connectivity provided by sensor networks is very crucial to their effectiveness. Early failure of sensor nodes due to death of a node can lead to coverage loss that requires coverage maintenance schemes. Similarly, possible destruction of nodes due to intrusion or explosion in the network creates the communication holes. Besides, the power sources of nodes, environmental factors, vibration, and failure of electronic components or software bugs may lead the death of the nodes accidentally, thereby affecting the coverage and connectivity of the original network. Many of the important applications of sensor networks demand autonomous mobility for the sensor nodes to maintain either the coverage or connectivity. However, most of the literatures consider the communication range is twice, even if greater than twice the sensing radius to repair the fault, thereby consuming more energy, as communication is the main source of energy consumption. We propose here a potential approach that let sensors work alternatively by identifying redundant sensing regions in high-density networks and to compensate the loss of both coverage and connectivity with communication range is equal to or less than twice the sensing range. For this we use the low mobility of nodes with minimum expenditure of energy and having knowledge of only their local neighborhood topology to repair both connectivity and coverage loss. We propose three different maintenance algorithms for connectivity, coverage and both connectivity to decide which neighbors to migrate, and to what distance, such that the energy expended is minimized and the faults are repaired by the low mobility nodes. The decision and movement is completely autonomous in the network, and involves movement of one-hop neighbors of a dead sensor node. We have also compared the performance of different algorithms in terms of the improvement in coverage, connectivity, average mobility distance and in terms of energy saving of the nodes, and the lifetime of the network, under our assumption that communication range is equal to or less than twice the sensing range.
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