A Bit-Serial Approximate Min-SumLDPCDecoder and FPGAImplementation
Anthony ChanCarusone
Abstract
Wepropose abit-serial LDPCdecoding scheme toreduceA.LDPCcodes andmin-sum decoding interconnect complexity infully-parallel low-density parity-check de- A binary (NN -M) LDPCcode, C,isthenull space ofasparse coders. Bit-serial decoding alsofacilitates efficient implementation of M N wordlength-programmable LDPCdecoding whichisessential forgear M xN parity-check matrix, H.Itcanalso bedescribed byabipartite shift decoding. Tosimplify theimplementation ofbit-serial decodinggraph, orTannergraph. Tannergraph ofanLDPC codeconsists of wepropose anewapproximation tothecheck update function inthe twosetofnodes. Checknodes{Cl, C2,...,CM}represent therows min-sum decoding algorithm. Thenewcheck update rule computes onlyofH andvariable nodes{VI V2,*.* VN}represent thecolumns. An theabsolute minimumandapplies acorrection tooutgoing messages if ' ' t required. Wepresent a650-Mbps bit-serial (480, 355)RS-based LDPC edgeconnects thechecknodecmtothevariable nodevnifandonly decoder implemented onasingle Altera Stratix EP1S80 FPGAdevice. To ifHmn isnonzero. Foracodewithafull-rank M xN parity-check ourknowledge, this isthefastest FPGA-based LDPCdecoder reported matrix, H,thecoderate isR = - M/N.We denote thesetof intheliterature. variables thatparticipate incheckCm asN(m) = {n:Hmn= 1}andthesetofchecks inwhichthevariable vnparticipates as