Constructing Quasi-Cyclic LDPCcodesUsinga Search Algorithm

Gabofetswe Malema

Published Jan 1, 2007• 0 citations

Abstract

Thisarticle presents asearch algorithm forcon-proposed algorithm withsomeobtained codessizes, girths structing regular andirregular quasi-cyclic LDPCcodes. Code andrates. Section IIIevaluates bit-error rateperformances rowsandcolumns aredivided intoj (column weight) andk (row-weight) ormoregroupsrespectively. Rowsorcolumns in a groupareconnected tothesamegroupandinorderof Section IV. appearance. Grouping ofrowsandcolumns forms sub-matrices.II. PROPOSEDQC-LDPCSEARCHALGORITHM Thesequential row-column connections ordercreates a cyclic structure insub-matrices. Therow-column constraint isobservedIn(8)quasi-cyclic column-weight twocodesareconstructed toavoid four-cycles. Theproposed algorithm isflexible comparedbasedonadistance graph representation. A desired girth g,is toother methods. Itobtains codes overawiderangeofgirths, obtained bysearching andconnecting tworowsthatareata rates andlengths. Bit-error ratesimulations showthatobtained codeshavegoodperformance withrandomly searched codesdistance ofatleastg Weextend thesearch algorithmiproposed performing better thatsequentially searched codes. in(8)toconstruct QC-LDPCwithcolumn-weights higher than two.LDPCcoderowsandcolumns aredivided intogroups

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