Decoding LDPC Codes With Locally Maximum-Likelihood Binary Messages

A new low-complexity message passing algorithm is described for decoding low-density parity-check (LDPC) codes by exchanging binary messages. The algorithm computes the local maximum-likelihood binary message (LMLBM) at each symbol node, given the combination of local channel information and partial syndrome components from adjacent parity check nodes. When channel information is quantized, the locally ML messages are pre-computed and stored in a dynamic global lookup table. The proposed algorithm uses memoryless extrinsic messages so that density evolution thresholds can be directly computed. Thresholds are obtained for regular ensembles, predicting good performance on quantized binary-input additive white Gaussian noise (biAWGN) channels.