Channel capacity of charge-constrained run-length limited codes

Abstract

The methods of information theory are applied to run-length limited codes with charge constraints. These self-clocking codes are useful in several areas of information storage, including magnetic recording, where it may be desirable to eliminate the dc component of the frequency spectrum. The channel capacity of run-length limited codes, with and without charge constraints, is derived and tabulated. The channel capacity specifies the maximum ratio of data/message bits achievable in implementing these codes and gives insight into the choice of codes for a particular task. The well-known frequency modulation (FM) code provides a simple example of these techniques.