9/12 2-D Modulation Code for Bit-Patterned Media Recording

Abstract

This paper presents a 9/12 2-D modulation code to overcome 2-D interference effects in bit-patterned media recording (BPMR) systems. Next-generation storage systems that are challenged by the superparamagnetic effect require new technologies to be developed, and for magnetic recording, BPMR technology is regarded to be one of the most promising candidates to extend area density beyond 1 Tb/in(2). BPMR systems not only help to reduce transition noise and non-linear bit shift, but they also simplify the tracking operation. Nevertheless, some challenges arise for BPMR systems from a signal processing point of view. One of the primary challenges in the systems is the 2-D interference due to the effects of both the along- and across-track intersymbol interference. Moreover, the effect of media noise and the physical limits of the electromechanical components also negatively impact the system performance. The proposed modulation code converts 9 b sequences of user data into 2-D output codewords in 6-by-2 arrays to avoid fatal interference as much as possible, and a reasonable Hamming distance is also ensured for the codeword set. The proposed code achieves gains of about 2 and 1 dB over a system without encoding and a system with 6/8 modulation coding at the same code rate, respectively. Moreover, the performance of the 9/12 2-D modulation codes according to the different array sizes is also investigated.