Sliding window coding technique for the variable length modulations

Variable length modulations such as 17RLL are widely applied to optical and magnetic recording systems. When a data bit sequence is modulated by the variable length rules, a symbol length cannot be decided uniquely. An encoder has to detect a restriction length of input data determined by the modulation rule and then modulates them according to the restriction length. This causes complexity of the encoding algorithm, especially when an additional data bit for the DSV control is inserted. In this paper, we propose a coding technique that enables fixed rate modulation of the variable length modulations by using state dependent modulation tables.