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Journal of Information Science and Engineering, Vol.18 No.5, pp.641-666 (September 2002)


A Hybrid Approach to Query Sets Broadcasting Scheduling
for Multiple Channels in Mobile Information Systems*

Ye-In Chang and Shih-Ying Chiu
Department of Computer Science and Engineering
National Sun Yat-Sen University
Kaohsiung, 804 Taiwan
E-mail: changyi@cse.nsysu.edu.tw

In this paper, we investigate the broadcasting scheduling over multiple channels for the case where a mobile client might need more than one page (i.e., a query set of data pages). Ke has proposed the SNV (Set-based version-Non-overlap Version) strategy for query set broadcast scheduling in multiple channels. In the SNV strategy, the data pages of the same query set are put together as much as possible, and the strategy tries to avoid scheduling two or more pages of one query set at the same time slot of different channels. However, there are two disadvantages with the SNV strategy: (1) a data page with high access frequency may be scheduled at a time slot near the end of the broadcast cycle, which will result in long access time for the whole query set; (2) it may increase the number of slots in a certain chain, which will result in a waste of bandwidth of the other channels. Therefore, in this paper, we propose an efficient broadcast scheduling strategy, a hybrid approach, to improve these two disadvantages. Basically, our hybrid approach combines the advantages of page-based and set-based strategies. Through our performance analysis and simulation, we show that our hybrid approach requires less total expected delay access time and creates a smaller number of slots and a smaller number of empty slots in one broadcast cycle compared to the SNV strategy.

Keywords: access time, bandwidth, broadcast schedule, mobile information systems, multiple channels

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August 30, 2001; accepted April 15, 2002.
Communicated by Jang-Ping Sheu, Makoto Takizawa and Myongsoon Park.
* This research was supported in part by the National Science Council of Republic of China under Grant No. NSC-89-2218-E-110-004 and National Sun Yat-Sen University.