Average transition density constraints for mitigating transition noise in magnetic recording

To mitigate transition noise in magnetic recording is to reduce the number of transitions that are written onto the media. This leads one to consider an average transition density (ATD) constraint. This new constraint reduces the ATD of sequences at the channel input and can be imposed in addition to other constraints. In this paper ATD constraint is imposed which is based on assigning a particular cost function to a finite-state transition diagram (FSTD) that presents a constrained system of binary NRZI sequences. At a normalized linear user density the performance of an unconstrained system satisfying an ATD constraint was simulated using a microtrack longitudinal (Lorentzian) recording model corrupted by transition noise and electronics noise.