Improved Sum-Min Decoding of LDPC Codes

EXIT charts are used to provide a bound for the performance of the Sum-Min algorithm for decoding of Low-Density Parity-Check codes. We present an optimal non-linear post-processing function of the check node outputs that achieves this bound. This function can be well approximated by a linear function, resulting in a simple normalization of the check node outputs, as proposed in [1] and [2]. A systematic approach for determining the optimal normalization factor using EXIT charts is presented.