Construction of simple runlength-limited codes

The authors describe a new technique for constructing fixed-length (d, k) runlength-limited block codes. The new codes are very close to block-decodable codes, as decoding of the retrieved sequence can be accomplished by observing (part of) the received codeword plus a very small part of the previous codeword. The basic idea of the new construction is to uniquely represent each source word by a (d, k) sequence with specific predefined properties, and to construct a bridge of β, 1⩽β<d, merging bits between every pair of adjacent words. The new constructions have the virtue that only one look-up table is required for encoding and decoding