On the combinatorial structure of a class of [m2,m-12,3] shortened Hamming codes and their dual-codes

  • Authors:
  • M. Esmaeili;A. Zaghian

  • Affiliations:
  • Department of Mathematical Sciences, Isfahan University of Technology, 84156-83111, Isfahan, Iran;Department of Mathematics, Malek-Ashtar University of Technology, Isfahan, Iran and Department of Mathematical Sciences, Teacher Training University of Tehran, Tehran, Iran

  • Venue:
  • Discrete Applied Mathematics
  • Year:
  • 2009

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Abstract

Let H"m be the binary linear block code with parity-check matrix H"m whose columns are all distinct binary strings of length m and Hamming weight 2. It is shown that H"m is an [n,k,d]=[m(m-1)2,(m-1)(m-2)2,3] code while the dual-code H"m^@? has dimension k^@? and minimum distance d^@? satisfying k^@?=d^@?=m-1. It is in general very difficult to find or even estimate the covering radius of a given code. It is shown here that the covering radius of H"m, denoted Cr(H"m), is @?m2@?. We also show that Cr(H"m^@?)=m(m-2)4 if m is even and Cr(H"m^@?)=(m-1)^24 if m is odd. Thus Cr(H"m^@?)~Cr(H"m)^2. The weight distribution of H"m^@? is given. This together with the MacWilliams identities results in an expression for the weight distribution of H"m. It turns out that the covering radius of H"m is equal to its external distance. From the Tanner graph perspective, the Tanner graphs of H"m and H"m^@? have girth 6. It is shown that the Tanner graphs of H"m"+"1^@? and H"m are essentially identical and are structurally representable by the complete graph K"m on m vertices.