Pairs of codes with prescribed Hamming distances and coincidences

  • Authors:
  • Vince Grolmusz

  • Affiliations:
  • Department of Computer Science, Eötvös University, Budapest, Hungary H-1117

  • Venue:
  • Designs, Codes and Cryptography
  • Year:
  • 2006

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Abstract

The main problem of coding theory is to construct codes with large Hamming-distances between the code-words. In this work we describe a fast algorithm for generating pairs of q-ary codes with prescribed pairwise Hamming-distances and coincidences (for a letter s 驴 {0,1,...,q 驴 1}, the number of s-coincidences between codewords a and b is the number of letters s in the same positions both in a and b). The method is a generalization of a method for constructing set-systems with prescribed intersection sizes (Grolmusz (2002) Constructing set-systems with prescribed intersection sizes. J Algorithms 44:321---337), where only the case q = 2 and s = 1 was examined. As an application, we show that the modular version of the classical Delsarte-inequality does not hold for odd, non-prime power composite moduli.