CONSTRAINED CODES FOR DIGITAL MAGNETIC RECORDING CHANNELS.

Abstract

Summary form only given. The construction of codes for the channel constraints that have figured prominently in the development of magnetic recording devices, namely run-length-limited (RLL) constraints and spectral null constraints, are considered. A typical digital magnetic recording channel is reviewed. A survey is then given of selected codes of practical interest and the theoretical methods that underly their construction, including optimal block codes used in magnetic tapes, as well as sequence-state and look-ahead codes found in magnetic and optical disks. Research avenues and practical code construction possibilities are considered.