Permutation (d, fc) codes: efficient enumerative coding and phrase length distribution shaping

In this correspondence, we introduce a new enumerative encoding method for (d, k) codes. The encoding algorithm, which is based on enumeration of multiset permutations, is conceptually simpler and computationally less expensive than other algorithms proposed thus far. We also describe a new application of enumerative encoding methods for phrase length distribution shaping of run-length-limited (RLL) sequences. We demonstrate that by reducing the probability of occurrence of long phrases in maxentropic RLL sequences, the frequency of patterns that account for most of the errors in magnetic recording systems can be decreased.