Preparata code

 

In coding theory, the Preparata codes form a class of non-linear double-error-correcting codes. They are named after who first described them in 1968.

Although non-linear over the Preparata codes are linear over Z4 with the .

Contents

Construction

Let m be an odd number, and n = 2^m-1. We first describe the extended Preparata code of length 2n+2 = 2^{m+1}: the Preparata code is then derived by deleting one position. The words of the extended code are regarded as pairs (X, Y) of 2m-tuples, each corresponding to subsets of the GF(2m) in some fixed way.

The extended code contains the words (X, Y) satisfying three conditions

  1. X, Y each have even weight;
  2. sum_{x in X} x = sum_{y in Y} y;
  3. sum_{x in X} x^3 + left(sum_{x in X} xright)^3 = sum_{y in Y} y^3.

The Preparata code is obtained by deleting the position in X corresponding to 0 in GF(2m).

Properties

The Preparata code is of length 2m+1 − 1, size 2k where k = 2m + 1 − 2m − 2, and minimum distance 5.

When m = 3, the Preparata code of length 15 is also called the Nordstrom–Robinson code.

Source

http://wikipedia.org/

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