| Summary: | 碩士 === 國立交通大學 === 資訊科學與工程研究所 === 94 === In monitoring applications of wireless sensor networks, queries are typically long-running and
executed over a specified period. Since each query is independently performed, wireless sensor networks
consume a considerable amount of energy when the number of queries increases. In this paper, we explore the feature of sharing
partial results of multiple queries so as to reduce the total number of messages incurred. Those queries sharing their partial results are referred to backbones.
Given a set of queries, we shall determine backbones with the purpose of minimizing the total number of messages. Explicitly, we first formulate the problem of selecting backbones and transform this problem into Max-Cut problem.
Specifically, given a set of queries, we derive a graph, where each vertex represents one query and the corresponding weight edge denotes the number of messages
reduced by sharing the partial results. According to the graph derived, we develop a heuristic algorithm SB (standing for Selecting Backbones) to derive a cut in which both backbones and non-backbones are determined. In order to evaluate the solution quality obtained by algorithm SB and compare its resulting backbone set with the optimal one, we devise an algorithm OOB (standing for Obtaining Optimal Backbones) to obtain the optimal solution.
Performance of these algorithms is comparatively analyzed and sensitivity analysis on several parameters, including the number of queries and the distribution of data sources for queries, is conducted. It is shown by our simulation results that by sharing the partial results, algorithm SB is able to significantly reduce the total number of messages, thereby saving a considerable amount of energy.
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