Soft-Decision Block Decoder

A method of soft-decision decoding a block code implemented by a soft-decision block decoder, the method comprising:

• receiving a soft-decision codeword encoded using the block code, wherein the soft-decision codeword comprises a plurality of codewords that at least comprise a most significant codeword that is a hard-decision representation of the soft-decision codeword and a least significant codeword;
• hard-decision decoding the most significant codeword to obtain a corrected codeword;
• identifying the number of bits flipped in the corrected codeword and bit positions of the flipped bits based on a difference between the most significant codeword and the corrected codeword;
• generating a set of codeword candidates based on the number of flipped bits and the bit positions of the flipped bits, wherein the set of codeword candidates are closest to the corrected codeword, a distance between each candidate codeword and the corrected codeword is less than a first threshold, and a distance between each candidate codeword and the most significant codeword is less than a second threshold;
• determining a soft-decision distance between each codeword candidate and the soft-decision codeword;
• and
• identifying a codeword candidate from among the set of codeword candidates that has the lowest soft-decision distance as an output of the soft-decision block decoder.