US Patent 7171603 Method and apparatus for encoding and decoding data

A deterministic structure for controlled distribution of weight-2 columns is proposed for a parity-check matrix H that reduces the occurrence of undetected frame errors and significantly enhances the code performance in comparison to a randomly-constructed parity-check matrix. H comprises a non-deterministic section H1 and a deterministic section H2, and wherein H2 comprises a first part comprising a column h having an odd weight greater than 2, and a second part comprising matrix elements for row i, column j equal to1 for i=j,1 for i=j+1,0 elsewhere.