Art of constructing low-complexity encoders/decoders for constrained blockcodes

A rate p : q block encoder is a dataword-to-codeword assignment from 2(p) p -bit datawords to 2(p) q-bit codewords, and the corresponding block decoder is the inverse of the encoder. When designing block encoders/decoders for constrained systems, often, more than 2p codewords are available, In this p aper, as our main contribution, we propose efficient heuristic computer alg orithms to eliminate the excess codewords and to construct low hardware com plexity block encoders/decoders. For (0, 4/4) and (0, 3/6) PRML constraints , block encoders/decoders generated using the proposed algorithms are compa rable in complexity to human-generated encoders/decoders, but are significa ntly simpler than lexicographical encoders/decoders.