With the increasing acceptance of wireless technology, mechanisms to efficiently transmit information to wireless clients are of interest. The environment under consideration is asymmetric in that the information server has much more bandwidth available, as compared to the clients. It has been proposed that in such systems, the server should broadcast the information periodically. Acharya et al. have proposed the use of a periodic dissemination architecture in the context of mobile systems, called Broadcast Disks. Using Broadcast Disks can construct a memory hierarchy in which the highest level contains a few items and broadcasts them with high frequency while subsequent levels contain more and more items and broadcast them with less and less frequency. In this way, one can establish a trade-off between access time for high-priority data and that of the low-priority items, where access time means that the time elapsed from the moment a client submits a query to the receipt of data of his (her) interest on the broadcast channel. A broadcast schedule specifies when and where each data page is to be transmitted. (Note that the smallest logical unit of the broadcast data is called a data page which is made up by data items. The time required to broadcast a data page is referred to as a time slot.) However, based on Acharya et al.'s algorithm, some broadcast slots may be unused, which resulting in the waste of bandwidth and the increase of access time, if it is not possible to evenly divide the number of broadcast pages assigned on a disk into the required number of chunks. (Note that each disk is split into a sequence of smaller units called chunks.) Therefore, in this thesis, we propose two efficient broadcast programs in which no empty slots is wasted. The first one is the binary-number-based approach and the second one is the complementary approach. In the binary-number-based approach, the broadcast frequency must be restricted to a value of 2^n , n¡Ù0, i.e. 1, 2, 4, 8..., etc; while in the complementary approach, there is no restriction on the broadcast frequency. From our performance analysis and simulation, we show that both of our proposed two approaches generate a small number of slots in one broadcast cycle (i.e., a shorter broadcast cycle) and shorter mean access time than Acharya et al. algorithm. Moreover, our first approach (the binary-number-based approach) requires a smaller number of slots in one broadcast cycle and shorter mean access time than the second approach (the complementary approach); however, there is some restriction on the chosen frequency in the first approach. Therefore, each of our proposed approaches has its own advantages and applicable domains, and both of them can avoid the wasteness of bandwidth and reduce the waiting time of clients.
| Identifer | oai:union.ndltd.org:NSYSU/oai:NSYSU:etd-0728100-114005 |
| Date | 28 July 2000 |
| Creators | Yang, Che-Nan |
| Contributors | Tei-Wei Kuo, Chien-I Lee, Ye-In Chang, San-Yih Hwang |
| Publisher | NSYSU |
| Source Sets | NSYSU Electronic Thesis and Dissertation Archive |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-0728100-114005 |
| Rights | not_available, Copyright information available at source archive |
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