Time-varying MTR codes for high density magnetic recording

Maximal transition run (MTR) codes eliminate the dominant error-event in high density magnetic recording by allowing at most two consecutive magnetic transitions. The maximum rate of such a code is upper bounded by the Shannon capacity 0.879. Unfortunately, the coding gain for MTR codes has not proven to be very significant since the distance benefit due to removing the dominant error-event barely makes up for the rate loss. In this paper, we describe a class of higher rate codes that eliminate the dominant high density error-event and provide improved coding gain. The new less restrictive constraints allow at most three consecutive transitions and have Shannon capacities as high as 0.925. Two high rate block codes with time-varying MTR constraints are presented. One code is rate 8/9 with block 9 and run-length constraint (d=0, k=11) and the other is rate 9/10 with block length 10 and (d=0, k=16).