Reduced-state sequence detection of multilevel partial-response signals

This work is concerned with the problem of designing reduced-complexity Viterbi decoders for the transmission of digital data over intersymbol interference channels. First, optimal state-grouping for constructing reduced-state trellises is presented and illustrative examples are given for multilevel transmission over partial-response channels of the type 1±Dⁿ, (1+D)², (1+D) ²(1-D), and (1+D)³(1-D). Then, the quaternary 1-D type partial-response channel is considered in more detail and a difference-matric algorithm employing state-reduction is derived and shown to result in a simple decoding scheme