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Journal of Combinatorial Optimization

, Volume 26, Issue 4, pp 687–708 | Cite as

(1+ε)-competitive algorithm for online OVSF code assignment with resource augmentation

  • Yuichi AsahiroEmail author
  • Kenta Kanmera
  • Eiji Miyano
Article
  • 116 Downloads

Abstract

This paper studies the online Orthogonal Variable Spreading Factor (OVSF) code assignment problem with resource augmentation introduced by Erlebach et al. (in STACS 2004. LNCS, vol. 2996, pp. 270–281, 2004). We propose a (1+1/α)-competitive algorithm with help of (1+⌈α⌉)lg h trees for the height h of the OVSF code tree and any α≥1. In other words, it is a (1+ε)-competitive algorithm with help of (1+⌈1/ε⌉)lg h trees for any constant 0<ε≤1. In the case of α=1 (or ε=1), we obtain a 2-competitive algorithm with 2lg h trees, which substantially improves the previous resource of 3h/8+2 trees shown by Chan et al. (COCOON 2009. LNCS, vol. 5609, pp. 358–367, 2009). In another aspect, if it is not necessary to bound the incurred cost for individual requests to a constant, an amortized (4/3+δ)-competitive algorithm with (11/4+4/(3δ)) trees for any 0<δ≤4/3 is also designed in Chan et al. (COCOON 2009. LNCS, vol. 5609, pp. 358–367, 2009). The algorithm in this paper gives us a new trade-off between the competitive ratio and the resource augmentation when α≥3 (or ε≤1/3), although the incurred cost for individual requests is bounded to a constant.

Keywords

Online OVSF code assignment problem Resource augmentation Competitive algorithm 

Notes

Acknowledgements

This work is partially supported by KAKENHI, 22700019 and 23500020.

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Copyright information

© Springer Science+Business Media, LLC 2012

Authors and Affiliations

  1. 1.Department of Information ScienceKyushu Sangyo UniversityFukuokaJapan
  2. 2.Department of Systems Design and InformaticsKyushu Institute of TechnologyFukuokaJapan

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