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  • Research Article
  • Open Access

Quasi-Cyclic LDPC Codes of Column-Weight Two Using a Search Algorithm

EURASIP Journal on Advances in Signal Processing20072007:045768

  • Received: 16 February 2006
  • Accepted: 6 February 2007
  • Published:


This article introduces a search algorithm for constructing quasi-cyclic LDPC codes of column-weight two. To obtain a submatrix structure, rows are divided into groups of equal sizes. Rows in a group are connected in their numerical order to obtain a cyclic structure. Two rows forming a column must be at a specified distance from each other to obtain a given girth. The search for rows satisfying the distance is done sequentially or randomly. Using the proposed algorithm regular and irregular column-weight-two codes are obtained over a wide range of girths, rates, and lengths. The algorithm, which has a complexity linear with respect to the number of rows, provides an easy and fast way to construct quasi-cyclic LDPC codes. Constructed codes show good bit-error rate performance with randomly shifted codes performing better than sequentially shifted ones.


  • Information Technology
  • Rate Performance
  • Search Algorithm
  • Quantum Information
  • Equal Size

Authors’ Affiliations

School of Electrical and Electronic Engineering, The University of Adelaide, North Terrace, Adelaide, SA, 5005, Australia


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© G. Malema and M. Liebelt. 2007

This article is published under license to BioMed Central Ltd. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.