4-ary (1,2) run-length limited code for optical storage channels

A 4-ary run-length limited (RLL) code with minimum run-length constraint d=1 and maximum run-length constraint k=2 is presented. The proposed code can be represented by a finite state diagram with two states. This is the lowest number of states necessary for representing the code yet presented. A simple decoding rule for the code is also introduced and a scheme for reducing the DC content of the coded sequence in the sense of multilevel running digital sum (RDS) is discussed