Exploiting spatial separations in CDMA systems with correlation constrained sets of Hadamard matrices

  • Authors:
  • Derek H. Smith;Francis H. Hunt;Stephanie Perkins

  • Affiliations:
  • Division of Mathematics and Statistics, University of Glamorgan, Pontypridd, Mid Glamorgan, UK;Division of Mathematics and Statistics, University of Glamorgan, Pontypridd, Mid Glamorgan, UK;Division of Mathematics and Statistics, University of Glamorgan, Pontypridd, Mid Glamorgan, UK

  • Venue:
  • IEEE Transactions on Information Theory
  • Year:
  • 2010

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Abstract

Spreading codes for code-division multiple-access (CDMA) systems are constructed based on Hadamard matrices and almost-bent functions. These codes can be assigned to a tessellation of hexagonal cells in such a way that codewords assigned to the same cell or to adjacent cells have zero cross-correlation. The nonzero cross-correlations in the code only apply to pairs of codewords assigned to nonadjacent cells. The codes have four times as many codewords as codes constructed from a single Hadamard matrix, which leads to significantly increased codeword re-use distances in comparison with the conventional use of a single Hadamard matrix with the same number of codewords per cell.