| Summary: | 碩士 === 國立中興大學 === 資訊科學系所 === 95 === Due to the rapid advancement in wireless technologies, retrieving instant, location-aware, and personalized information has become popular. The information provider (i.e., a server) should service a lot of competitive mobile users, broadcast is thus a reasonable strategy to achieve this requirement. Unfortunately, the battery power of mobile devices is always limited. Therefore, how to retrieve desired data using the minimal power becomes a pressing need. Prior research showed that indexing can help us save power, but it may have the side-effect of long access/tuning time when multiple items are accessed at a time. In this study, we propose a new scheme for multiple data-item queries over multiple channels. The scheme can ensure each mobile user accesses multiple data items effectively by using two hash functions. Moreover, no matter how many data items are requested, only two times of tuning are needed to download the index information. As a result, it can save a lot of power. Besides, we propose an alternative scheme that can fully employ the bandwidth of the index channel, i.e., eliminating the unused space caused by hashing in the index channel. The experiments show that each mobile user can download their own desired information in a fixed tuning time. Likewise, we also improve the bandwidth utilization of the index channel at a little cost of tuning time.
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