User Areal Density Optimization for Conventional and 2D Detectors/Decoders (original) (raw)
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Two-dimensional magnetic recording (TDMR) is a novel recording architecture intended to support densities beyond those of conventional recording systems. The gains from TDMR come primarily from more powerful coding and signal processing algorithms that allow the bits to be packed more tightly on the disk, and yet be retrieved with acceptable error rates. In this paper, we present some preliminary results for an advanced channel model based on micromagnetic simulations, coined the Grain Flipping Probability model. This model requires a one-time computationally complex characterization phase, but subsequently provides fast and accurate two-dimensional (2-D) readback waveforms that include effects captured from micromagnetic simulations and the statistical effects derived from the granularity of the recording medium. We also show the performance of several detectors over a pre-existing TDMR channel model directly as a function of channel density rather than the signal-to-noise ratio (SNR).
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IEEE Transactions on Magnetics
Two-dimensional magnetic recording (TDMR) together with shingled magnetic recording (SMR) are technologies proposed to extend the life of conventional granular magnetic recording. The grain flipping probability (GFP) model has been proposed to mimic the performance of micromagnetic ( μ-mag) simulations for the purpose of signal reproduction. Other work in TDMR includes the proposal of a Gaussian mixture model (GMM) that produces improved likelihood information at the output of the detector, combined with low density parity check (LDPC) codes. The contribution of this paper is threefold. First, we aim to simulate a TDMR/SMR recording system with the GFP model, both with and without the GMM detector, and with various random and structured LDPC codes, of both 4 k and 16 k block lengths, to determine areal densities that might be achieved. Second, we perform a comparison of the various model order reduced (MOR) GFP implementations to compare the effect of writing with various factors ta...
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2002
Digital signal processing and coding are increasingly being recognized as a cost-efficient approach in achieving substantial areal density gains while preserving the high reliability of disk drives, although historically advances in head and media technologies have been the main driving force behind areal density growth. The recent advances in capacity-approaching codes hold the promise to push the areal density to the ultimate limit. In this article the various configurations regarding the interplay between soft detection and soft decoding through an iterative process, as it applies to the magnetic recording channel, are presented. In particular, the state of the art in turbo and turbo-like coding, including LDPC coding, is reviewed, and the serial concatenation of these coding schemes with inner generalized PR channels in a turbo equalization structure is described. Finally, an attempt is made to assess the performance and limitations of these AWGN channel-capacity-approaching codes when applied to the magnetic recording channel.
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IEEE Communications Magazine, 2000
Digital signal processing and coding are increasingly being recognized as a cost-efficient approach in achieving substantial areal density gains while preserving the high reliability of disk drives, although historically advances in head and media technologies have been the main driving force behind areal density growth. The recent advances in capacity-approaching codes hold the promise to push the areal density to the ultimate limit. In this article the various configurations regarding the interplay between soft detection and soft decoding through an iterative process, as it applies to the magnetic recording channel, are presented. In particular, the state of the art in turbo and turbo-like coding, including LDPC coding, is reviewed, and the serial concatenation of these coding schemes with inner generalized PR channels in a turbo equalization structure is described. Finally, an attempt is made to assess the performance and limitations of these AWGN channel-capacity-approaching codes when applied to the magnetic recording channel.
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The feasibility of magnetic recording at 1 Terabit per square inch
IEEE Transactions on Magnetics, 2000
This paper explores the feasibility of implementing conventional magnetic recording technology at densities up to one Terabit per square inch. The key limiting physical factor is the superparamagnetic effect (thermal stability) in the recording medium. Ambient thermal energy can cause the magnetic signals to decay. The requirement for thermal stability over periods of years dictates a lower limit to the size of magnetic grains (switching units) in the recording medium. To achieve the highest areal densities, it will be necessary to use a magnetic recording configuration capable of writing and storing data on very small magnetic grains together with a signal processing system capable of recovering data reliably when each bit is recorded on very few such grains. In addition to these physical effects, there are a number of practical engineering factors that must be considered: tolerances on the head geometry, reliability of head-disk interface, track-following accuracy.
Read Channel Modeling for Detection in Two-Dimensional Magnetic Recording Systems
IEEE Transactions on Magnetics, 2009
In this paper, we describe a read channel model for detector design for two-dimensional magnetic recording (TDMR) system, a novel strategy for recording at upto 10 Tb/in 2 . We describe a scheme for (1) modeling of the recording medium, (2) modeling of the write/ readback process, and (3) an experimental method for the characterization of noise in the TDMR channel, occurring due to irregularities in the bit-boundaries in the recording medium, that can be used for detection purposes.
Journal of Applied Physics, 2015
Shingled Magnetic Recording (SMR) is an upcoming technology to see the hard disk drive industry over until heat assisted magnetic recording or another technology matures. In this work, we study the impact of variations in media parameters on the raw channel bit error rate (BER) through micromagnetic simulations and the grain flipping probability channel model in the SMR situation. This study aims to provide feedback to media designers on how media property variations influence the SMR channel performance. In particular, we analyse the effect of variations in the anisotropy constant (Ku), saturation magnetization (Ms), easy axis (ez), grain size (gs), and exchange coupling (Ax), on the written micromagnetic output and the ensuing hysteresis loop. We also compare these analyses with the channel performance on signal to noise ratio (SNR) and the raw channel BER.
IEEE Transactions on Magnetics, 2004
In this work, we present three magnetic force microscopy (MFM)-compatible pulse-width-modulation (PWM) coding scheme to be employed in scanning-probe storage devices. For each code, analytical models describing the code length utilization [CLU, i.e., non-return-to-zero (NRZ) code length to PWM code length ratio] and the signal-to-quantization noise ratio (SQNR) resulting from the granularity of the media are derived. To verify the models, a micromagnetic model was constructed. Using a proposed variable-length PWM coding scheme with 3 bits/symbol, 30-nm tip diameter, and a fractional step of 20% of the initial mark, a 82% increase in areal density over optimized regular NRZ single-bit coding is shown to be achievable (i.e., 1.26 Tb/in 2 ) with an SQNR of 17.2 dB and an overall SNR of 13.1 dB.