On the construction of constrained codes employing sequence replacement techniques

General construction methods of prefix synchronized codes and runlength limited codes are presented, which make use of so-called sequence replacement techniques. These techniques provide a simple and efficient conversion of data words into codewords of a constrained block-code, where subsequences violating the imposed constraints are replaced by encoded information to indicate their relative positions in the data word. Several constructions are proposed for constrained codes with low error propagation, and for variable length constrained codes. The coding algorithms have a low computational and hardware complexity. The rate of the constructed codes approaches the theoretical maximum. It is feasible to apply these high rate constrained block codes in communication and recording systems