A simple one-sweep algorithm for optimal APP symbol decoding of linear block codes

Soft-input/soft-output symbol decoding plays a significant role in iterative decoding. We propose a simple optimal soft-input/soft-output symbol decoding algorithm for linear block codes which requires one forward recursion using a trellis. For many codes the decoding complexity is lower than previous methods, such as the algorithm by Bahl et al. (1974), and the decrease is shown at its most when decoding Hamming codes.