Abstract
We consider the problem of orthogonal variable spreading Walsh code assignments. The aim is to provide assignments that can avoid both complicated signaling from the BS to the users and blind rate and code detection amongst a great number of possible codes. The assignments considered here use partitioning of all users into several pools. Each pool can use its own codes, which are different for different pools. Each user has only a few codes assigned to it within the pool. We state the problem as a combinatorial one expressed in terms of a binary n × k matrix M where n is the number of users and k is the number of Walsh codes in the pool. A solution to the problem is given as a construction of a matrix M which has the assignment property defined in the paper. Two constructions of such M are presented under different conditions on n and k. The first construction is optimal in the sense that it gives the minimal number of Walsh codes — assigned to each user for given n and k. The optimality follows from a proved necessary condition for the existence ofM with the assignment property. In addition, we propose a simple algorithm of optimal assignment for the first construction.
Similar content being viewed by others
References
Viterbi, A.J., CDMA: Principles of Spread Spectrum Communication, Reading, MA: Addison-Weseley, 1995.
Adachi, F., Sawahashi, M., and Okawa, K., Tree-Structured Generation of Orthogonal Spreading with Different Lengths for Forward Link of DS-CDMA Mobile Radio, Electron. Lett., 1997, vol. 33, no. 1, pp. 27–28.
Dinan, E.H. and Jabbari, B., Sreading Codes for Direct Sequence CDMA and Wideband CDMA Cellular Networks, IEEE Commun. Mag., 1998, vol. 36, no. 9, pp. 48–59.
Minn, T. and Siu, K.-Y., Dynamic Assignment of Orthogonal Variable-Spreading-Factor Codes in W-CDMA, IEEE J. Sel. Area. Comm., 2000, vol. 18, no. 8, pp. 1429–1440.
Tseng, Y.-C., Chao, C.-M., and Wu, S.-L., Code Placement and Replacement Strategies for Wideband CDMA OVSF Code Tree Management, in Proc. IEEE Global Telecommunications Conf. (GLOBECOM’ 01), San Antonio, Texas, USA, 2001, vol. 1, pp. 562–566.
Dell’Amico, M., Merani, M.L., and Maffioli, F., Efficient Algorithms for the Assignment of OVSF Codes in Wideband CDMA, in Proc. IEEE Int. Conf. on Communications (ICC’2002), New York, USA, 2002, vol. 5, pp. 3055–3060.
Tsai, S., Khaleghi, F., Oh, S.-J., and Vanghi, V., Allocation of Walsh Codes and Quasi-Orthogonal Functions in CDMA2000 Forward Link, in Proc. 54th IEEE Vehicular Technology Conf. (VTC Fall 2001), Atlantic City, NJ, USA, 2001, vol. 2, pp. 747–751.
Hall, M., Jr., Combinatorial Theory, New York: Wiley, 1998. Reprint of the 1986 2nd ed.
Author information
Authors and Affiliations
Corresponding author
Additional information
Original Russian Text © B.S. Tsybakov, A.B. Tsybakov, 2012, published in Problemy Peredachi Informatsii, 2012, Vol. 48, No. 4, pp. 41–49.
Rights and permissions
About this article
Cite this article
Tsybakov, B.S., Tsybakov, A.B. On Walsh code assignment. Probl Inf Transm 48, 334–341 (2012). https://doi.org/10.1134/S0032946012040035
Received:
Published:
Issue Date:
DOI: https://doi.org/10.1134/S0032946012040035