Abstract

Generally, an intertrack interference (ITI) is a critical problem in bit-patterned magnetic recording (BPMR) systems that can attain an areal density (AD) up to 4 Tb/in <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . Unavoidably, at high ADs, a very narrow track width must be employed, leading to severe ITI and unacceptable system performance. To tackle the ITI; therefore, this article introduces a novel ITI suppression technique for coded dual-track dual-head (DTDH) BPMR systems. At the first turbo iteration, the weighted readback signal of the adjacent track served as an estimated ITI signal is utilized for subtracting from the target readback signal to subside the ITI effect, before passing the refined readback signal to a turbo equalizer. Nonetheless, for the second turbo iteration onwards, the estimated ITI signal generated by the soft information obtained from a decoder at each turbo iteration will be then employed to subtract from the target readback signal during the turbo decoding process. Computer simulation results demonstrate that the proposed system can provide better performance than the DTDH system using a hard ITI suppression technique as well as the conventional system using one read head to decode one data track for all ADs, because the proposed technique can estimate the ITI signal well. Furthermore, when considering the recording system under the effects of media noise and track mis-registration, we also found that the proposed system is more robust than other systems.

Highlights

  • A current perpendicular magnetic recording (PMR) technology used to store data in hard disk drives is approaching its limit at 1 Terabit per square inch (Tb/in2), technically known as a super-paramagnetic limit [1]

  • In [20], the intertrack interference (ITI) suppression technique for the coded dual-track dual-head (DTDH) bit-patterned magnetic recording (BPMR) channel with a staggered array island medium was presented, which employed the hard decision from the low-density parity-check (LDPC) decoder to estimate the ITI signal

  • To alleviate the ITI, we propose a novel ITI suppression technique for a coded DTDH BPMR system by utilizing the soft information of the adjacent track obtained from the LDPC decoder to estimate the ITI signal and subtracting it from the associated readback signal at each turbo iteration

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Summary

INTRODUCTION

A current perpendicular magnetic recording (PMR) technology used to store data in hard disk drives is approaching its limit at 1 Terabit per square inch (Tb/in2), technically known as a super-paramagnetic limit [1]. Because the size of read head is normally larger than the island, it covers many islands while reading data in both along- and cross-track directions This definitely causes the readback signal to experience with both intersymbol interference (ISI) and intertrack interference (ITI) [3], whose severity depends on an operating AD. This article presents a novel ITI suppression technique for a coded DTDH BPMR channel with regular island arrangement, which is an extended work from [22], where we thoroughly explain the proposed ITI suppression technique on how it operates and investigate its performance more in the presence of media noise and TMR. The proposed system can provide better bit-error rate (BER) performance if compared to the DTDH system with hard ITI suppression technique [20] and the conventional system for all ADs, when the recording system severely encounters both media noise and TMR.

CHANNEL MODEL
SOFT ITI SUPPRESSION TECHNIQUE
TARGET AND EQUALIZER DESIGN
NUMERICAL RESULT
CONCLUSION
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