Patent ID: 8392789

Claim:
A digital system comprising: a digital signal processor; and a memory configured to store software instructions, wherein when executed by the processor, the software instructions cause the digital system to perform a method for decoding a codeword in a data stream encoded according to a low density parity check (LDPC) code having an m×j parity check matrix H, the method comprising: initializing each of j variable nodes in a graph representation of the parity check matrix H with a soft value L(q j ) based on a jth symbol in the codeword, wherein the graph representation comprises m check nodes and j variable nodes and wherein a check node m provides a row value estimate R mj to a variable node j and a variable node j provides a column value estimate L(q mj ) to a check node m if H(m,j) contains a 1; computing row value estimates R mj for each check node m, wherein amplitudes of only a subset of column value estimates L(q mj ) provided to the check node m are computed; computing soft values L(q j ) for each variable node j based on the computed row value estimates R mj ; determining whether the codeword is decoded based on the soft values L(q j ); and terminating decoding when the codeword is decoded.