| Summary: | 碩士 === 國立臺灣大學 === 生物產業機電工程學研究所 === 97 === There are a lot of issues which need to be considered due to the limited power, the communication range, and the programming ability of wireless sensor nodes. In order to improve the lifetime of wireless sensor networks (WSNs), a number of routing algorithms have been proposed to adjust the data transmission between sensor nodes. Besides the energy efficiency, however, reliability of data transmission and cluster forming method, maintenance of the sensing coverage over the entire monitored area are also essential. In construction of projects that involve operational strategies to responds to specific emergency events such as medical healthcare, battlefield surveillance, or illegal smuggling, the primary concern is to preserve all valuable data acquired from the targeted area without any losing. Hence, this work proposed a novel energy-aware coverage-preserving hierarchical routing (ECHR) algorithm. The performance of ECHR algorithm was evaluated by simulations. In simulations, the ECHR algorithm can maximize the on duty time of full coverage. This work also applied the ECHR algorithm in wireless sensor node with OctopusII platform.
The basic idea of the proposed ECHR algorithm is to take the remaining energies of the nodes as well as the coverage redundancy of its sensing ranges into consideration while selecting cluster heads. Intuitively, the sensor nodes deployed in a densely populated area have the higher probability to be selected as cluster heads in each round. These nodes are frequently chosen to be cluster heads, because the loss of nodes from the densely populated area is not significant for the network coverage. In addition, an energy-aware hierarchical routing mechanism was also proposed to determine the optimal route. Extensive series simulations were conducted to analyze the performance of the ECHR algorithm applying to the network with different weight factors of the cluster head selection mechanism and the adaptive energy-aware hierarchical routing mechanism. The simulation results demonstrate that the proposed protocol is able to increase the duration of network on duty and provide up to 59 % of extra service time with 100% sensing coverage ratio comparing with other existing protocols.
Most presented researches about routing algorithms only evaluated the performance under simulations. In order to evaluate the feasibility of ECHR algorithm in realistic applications, this work has developed the ECHR algorithm with NesC program on TinyOS. All of experimental tests in laboratory and outdoor environment used wireless sensor nodes, OcotpusII. The experimental results demonstrate that the adaptive routing mechanism of the ECHR algorithm is able to reduce the data loss rate.
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