Quasicyclic codes of index l over Fq viewed as Fq[x]-submodules of Fql[x]/ċ xmċ1ċ

  • Authors:
  • Kristine Lally

  • Affiliations:
  • Department of Mathematics, RMIT University, Melbourne, Australia

  • Venue:
  • AAECC'03 Proceedings of the 15th international conference on Applied algebra, algebraic algorithms and error-correcting codes
  • Year:
  • 2003

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Abstract

Quasicyclic codes of length n = ml and index l over the finite field Fq are linear codes invariant under cyclic shifts by l places. They are shown to be isomorphic to the Fq[x]/ 〈xm - 1〉-submodules of Fql[x]/ 〈xm - 1〉 where the defining property in this setting is closure under multiplication by x with reduction modulo xm - 1. Using this representation, the dimension of a 1-generator code can be determined straightforwardly from the chosen generator, and improved lower bounds on minimum distance are developed. A special case of multigenerator codes, for which the dimension can be algebraically recovered from the generating set is described. Every possible dimension of a quasicyclic code can be obtained in some such special form. Lower bounds on minimum distance are also given for all multi-generator quasicyclic codes.