Trellis codes for (1,k) E/sup 2/PR4ML with squared distance 18

Finite truncation depth codes are obtained using periodically pruned module N trelises. One approach uses a runlength limited (d,k)=(1,7) code with rate R=2/3 as the underlying code. Another approach which results in a lower complexity detector trellis uses a rate R=3/5 sliding-block code that prohibits NRZI "10001" and adheres to a (d,k)=(1,8) constraint. The design of the module N trellis is described, and sufficient conditions for finite truncation depth are developed and applied to obtain several codes.