Improved on-line broadcast scheduling with deadlines

  • Authors:

  • Feifeng Zheng;Stanley P. Y. Fung;Wun-Tat Chan;Francis Y. L. Chin;Chung Keung Poon;Prudence W. H. Wong

  • Affiliations:

  • School of Management, Xi’an JiaoTong University, China;Department of Computer Science, University of Leicester, United Kingdom;Department of Computer Science, The University of Hong Kong, Hong Kong, China;Department of Computer Science, The University of Hong Kong, Hong Kong, China;Department of Computer Science, City University of Hong Kong, China;Department of Computer Science, University of Liverpool, United Kingdom

  • Venue:
  • COCOON'06 Proceedings of the 12th annual international conference on Computing and Combinatorics
  • Year:
  • 2006

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Abstract

We study an on-line broadcast scheduling problem in which requests have deadlines, and the objective is to maximize the weighted throughput, i.e., the weighted total length of the satisfied requests. For the case where all requested pages have the same length, we present an online deterministic algorithm named BAR and prove that it is 4.56-competitive. This improves the previous algorithm of Kim and Chwa [11] which is shown to be 5-competitive by Chan et al. [4]. In the case that pages may have different lengths, we prove a lower bound of Ω(Δ/logΔ) on the competitive ratio where Δ is the ratio of maximum to minimum page lengths. This improves upon the previous $\sqrt{\Delta}$ lower bound in [11,4] and is much closer to the current upper bound of ($\Delta+2\sqrt{\Delta}+2$) in [7]. Furthermore, for small values of Δ we give better lower bounds.