A concatenated decoding scheme for (1-D) partial response with matched spectral-null coding

Since the (1-D) partial response channel has a spectral null at DC, applying 3 DC-free code raises the minimum squared Euclidean distance from 2 for the uncoded channel to 4 for the matched spectral-null coded channel. Due to the complexity of the optimal decoder, there is interest in suboptimal decoders which have roughly the same performance as the optimal decoder. For DC-free block codes, we present a sub-optimal approach which treats the channel and the code separately using a two stage decoding process. The first stage consists of a maximum-likelihood detector for the uncoded (1-D) channel. The second stage is an error-event detector which uses the DC-free block code to detect and correct minimum distance error-events