, 56:89 | Cite as

A Constant-Competitive Algorithm for Online OVSF Code Assignment

  • F. Y. L. Chin
  • H. F. TingEmail author
  • Y. Zhang


Orthogonal Variable Spreading Factor (OVSF) code assignment is a fundamental problem in Wideband Code-Division Multiple-Access (W-CDMA) systems, which plays an important role in third generation mobile communications. In the OVSF problem, codes must be assigned to incoming call requests with different data rate requirements, in such a way that they are mutually orthogonal with respect to an OVSF code tree. An OVSF code tree is a complete binary tree in which each node represents a code associated with the combined bandwidths of its two children. To be mutually orthogonal, each leaf-to-root path must contain at most one assigned code. In this paper, we focus on the online version of the OVSF code assignment problem and give a 10-competitive algorithm (where the cost is measured by the total number of assignments and reassignments used). Our algorithm improves the previous O(h)-competitive result, where h is the height of the code tree, and also another recent constant-competitive result, where the competitive ratio is only constant under amortized analysis and the constant is not determined. We also improve the lower bound of the problem from 3/2 to 5/3.


Wideband code-division multiple-access Online algorithms Competitive analysis Lower bounds 


  1. 1.
    Chan, W.T., Chin, F.Y.L., Ye, D., Zhang, Y., Zhu, H.: Frequency allocation problem for linear cellular networks. In: Proceedings of the 17th Annual International Symposium on Algorithms and Computation. Lecture Notes in Computer Science, vol. 4288, pp. 61–70. Springer, Berlin (2006) Google Scholar
  2. 2.
    Chan, W.T., Chin, F.Y.L., Ye, D., Zhang, Y., Zhu, H.: Greedy online frequency allocation in cellular networks. Inf. Process. Lett. 102(2–3), 55–61 (2007) CrossRefMathSciNetGoogle Scholar
  3. 3.
    Chan, W.T., Chin, F.Y.L., Ye, D., Zhang, Y., Zhu, H.: Online frequency allocation in cellular networks. In: Proceedings of the 19th ACM Symposium on Parallelism in Algorithms and Architectures, pp. 241–249 (2007) Google Scholar
  4. 4.
    Chin, F.Y.L., Zhang, Y., Zhu, H.: Online OVSF code assignment in cellular networks. In: Proceedings of the 3rd International Conference on Algorithmic Aspects in Information and Management. Lecture Notes in Computer Science, vol. 4508, pp. 191–200. Springer, Berlin (2007) CrossRefGoogle Scholar
  5. 5.
    Caragiannis, I., Kaklamanis, C., Papaioannou, E.: Efficient on-line frequency allocation and call control in cellular networks. Theory Comput. Syst. 35(5), 521–543 (2002). A preliminary version of the paper appeared in SPAA 2000 zbMATHCrossRefMathSciNetGoogle Scholar
  6. 6.
    Erlebach, T., Jacob, R., Mihalak, M., Nunkesser, M., Szabo, G., Widmayer, P.: An algorithmic view on OVSF code assignment. Algorithmica 47, 269–298 (2007) zbMATHCrossRefMathSciNetGoogle Scholar
  7. 7.
    Forišek, M., Katreniak, B., Katreniaková, J., Královič, R., Královič, R., Koutný, V., Pardubská, D., Plachetka, T., Rovan, B.: Online bandwidth allocation. In: Proceedings of the 16th Annual European Symposium on Algorithms. Lecture Notes in Computer Science, vol. 4698, pp. 546–557. Springer, Berlin (2007) Google Scholar
  8. 8.
    Li, X.Y., Wan, P.J.: Theoretically good distributed CDMA/OVSF code assignment for wireless ad hoc networks. In: Proceedings of the 11th Annual International Conference of Computing and Combinatorics, pp. 126–135 (2005) Google Scholar
  9. 9.
    McDiarmid, C., Reed, B.A.: Channel assignment and weighted coloring. Networks 36(2), 114–117 (2000) zbMATHCrossRefMathSciNetGoogle Scholar
  10. 10.
    Minn, T., Siu, K.Y.: Dynamic assignment of orthogonal variable-spreading factor codes in W-CDMA. IEEE J. Sel. Areas Commun. 18(8), 1429–1440 (2000) CrossRefGoogle Scholar
  11. 11.
    Rouskas, A.N., Skoutas, D.N.: OVSF codes assignment and reassignment at the forward link W-CDMA 3G systems. In: Proceedings of the 13th IEEE International Symposium on Personal, Indoor and Mobile Radio Communications Google Scholar
  12. 12.
    Tomamichel, M.: Algorithmische Aspekte von OVSF Code Assignment mit Schwerpunkt auf Offline Code Assignment. Student thesis at ETH Zürich (2004) Google Scholar
  13. 13.
    Wan, P.J., Li, X.Y., Frieder, O.: OVSF-CDMA code assignment in wireless ad hoc networks. In: Proceedings of DIAL M-POMC 2004 Joint Workshop on Foundations of Mobile Computing, pp. 92–101 (2004) Google Scholar

Copyright information

© Springer Science+Business Media, LLC 2008

Authors and Affiliations

  1. 1.Department of Computer ScienceThe University of Hong KongHong KongHong Kong

Personalised recommendations