| Summary: | 碩士 === 國立交通大學 === 網路工程研究所 === 97 === We study the problem of a wireless sensor network system which is deployed far from the base station and is for collecting heterogeneous types of data. Users make queries of real-time, collective data inside the network. For example, what is the average temperature in the last 2 hours? For avoiding unnecessary data transmissions and enhancing data security, the collected data are stored inside the sensor network itself instead of transmitting all the data back to the base station. We propose a two-tier, cluster-based, data-centric storage system for the studied scenario. Our goals are to achieve efficient storage and retrieval of collective data, and to extend system lifetime through load balancing. In our system, the network is virtually divided into clusters. Different types of sensed data will be stored in their corresponding clusters. Inside a cluster, data is replicated in a ring-based fashion. As for deciding which cluster the data will be forwarded to, we propose two methods: hashing and table mapping. Both methods provide load balancing to prolong network lifetime.
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