›› 2012, Vol. 32 ›› Issue (2): 62-67.doi: 10.3780/j.issn.1000-758X.2012.02.010

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 Quasi-cycleLDPCConstructionMethod BasedonProtographExpansion 

 GONG  Xian-Feng1, TAO  Xiao-Fen1,QIU  Le-De2   

  1.  (1 Xi′anDivisionofChinaAcadamyofSpaceTechnology,Xi′an710000)
     (2 ChinaAcadamyofSpaceTechnology,Beijing100094)
  • Received:2011-03-09 Revised:2012-04-25 Online:2012-04-25 Published:2012-04-25

Abstract: Theperformanceoflowdensityparitycheckcode(LDPC)basedonprotopraphexpansiongreatlydependsontheexpansionmethod.AnewQC-LDPCconstructionmethodwasproposed.Twomainstepsintheparitycheckmatrixconstructionincludethemulti-edgeseliminationofprotographandquasi-cycleexpansion.Thefirststepmakelocalgirthmaximumundertheconstraintofedgepermutation.Inthesecondstep,optimumshiftvaluesofthepermutationmatriceswereobtainedbysearchingtheclosedloopswithinthespecifiedlengthandcomparingthelengthandapproximatecycleextrinsicmessagedegree(ACE)ofcycles,aimingatreducingsmallcycleswithlowconnectivitywhichwasharmfultothecodeperformance.Forprotographwithoutmulti-edges,theonlystepwasthequasicycleexpansion.Asprovedbysimulation,theconstructedQC-LDPChasexcellentperformanceinbothdecodingthresholdanderrorflooraspects.

Key words: Quasi-cyclic low-density parity-check code, Protograph, Progressive edge-growth, Approximate cycle extrinsic message degree, Satellite communication