Soft-Input Inner Decoder for the Davey-MacKay Construction

The Davey-MacKay (DM) construction is a promising concatenated coding scheme for the binary-input, binary-output, insertion-deletion-substitution (IDS) channel. Many practical channels however have continuous output. We therefore develop a soft-input inner decoder for this coding scheme under a cascaded channel model consisting of the IDS channel followed by a binary-input, continuous-output, additive white Gaussian noise (AWGN) channel. We show that at low signal-to-noise ratios (SNRs), applying the proposed inner decoder to the unquantized AWGN channel output, yields significant performance improvements over the original coding scheme when the channel output is 1-bit quantized, although the performance gains do decrease as SNR increases.