Codes preventing quasi-catastrophic error propagation in partial-response systems

The problem of preventing quasi-catastrophic error propagation in maximum-likelihood and reduced-state sequence detection for multilevel partial-response channels with transfer functions (1-D^P) and (1+D^P) is studied. M-ary channel input sequences that limit the length of minimum distance error events to L symbols are exhaustively characterized by finite-state transition diagrams. An efficient procedure for computing the capacity associated with these transition diagrams is given. Efficient constrained codes that can be readily implemented by finite-state encoders and block decoders with small error propagation are constructed