Constrained codes and systems

In digital optical and magnetic recording systems the data is written along tracks. Namely, we visualize the recording device as containing one long strip of data. To ensure reliable recording and readback, the raw data typically undergoes a constrained coding stage that matches the recorded data with constraints that are dictated by physical characteristics of the recording device. The author presents a new coding scheme for the 2-D (0,1)-RLL constraint. This scheme is based on defining a certain simple probability measure on the arrays that obey this constraint. A variable-rate version of the new coding scheme has an average rate which is only 0.1% below capacity.