A complementary approach to data broadcasting in mobile information systems

摘要

Acharya et al. have proposed the use of a periodic dissemination architecture in the context of mobile systems, called Broadcast disks. This strategy can construct a memory hierarchy where 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 the time elapsed from the moment a client submits a query to the receipt of data of his (her) interest on the broadcast channel. However, based on Acharya et al.'s algorithm, some broadcast slots may be unused, which results in the waste of bandwidth and the increase of access time. Therefore, in this paper, we propose an efficient broadcast program, the complementary approach, in which no empty slot is wasted. The basic idea of the complementary approach is to move some pages which are located near the end of a broadcast cycle to those empty slots which occur before these pages. Therefore, finally, the total number of slots in a broadcast cycle is equal to the one computed from Acharya et al.'s algorithm minus the number of empty slots. Obviously, our complementary approach generates a small number of slots in one broadcast cycle and shorter mean access time than Acharya et al.'s algorithm.