Modifying Viterbi Algorithm to Mitigate Intertrack Interference in Bit-Patterned Media

Nabavi, S.; Kumar, B. V. K. Vijaya; Zhu, Jian‐Gang

doi:10.1109/tmag.2007.893479

Cited by 55 publications

(28 citation statements)

References 8 publications

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“…To reduce ITI, Nabavi [7] proposed a modified trellis for BPMR. In [8], Nabavi suggested a 2D equalizer with a PR target and optimized equalizer coefficients to eliminate ISI and ITI. Based on Nabavi [7,8], a hybrid 2D equalizer was proposed by Wang [9] to improve channel estimation when ITI is known.…”

Section: Introductionmentioning

confidence: 99%

“…In [8], Nabavi suggested a 2D equalizer with a PR target and optimized equalizer coefficients to eliminate ISI and ITI. Based on Nabavi [7,8], a hybrid 2D equalizer was proposed by Wang [9] to improve channel estimation when ITI is known. Additionally, to mitigate 2D interference, Kim [10] proposed a 2D soft-output Viterbi algorithm (2D SOVA), which is also known as a parallel detection model, for holographic data storage, then developed an iterative 2D SOVA for bit-patterned media [11].…”

Section: Introductionmentioning

confidence: 99%

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Effective Generalized Partial Response Target and Serial Detector for Two-Dimensional Bit-Patterned Media Recording Channel Including Track Mis-Registration

Nguyen

Lee

2020

Applied Sciences

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With the development of 5G technology, programs are gradually moving to cloud services. This leads to an increasing demand for storage. In the field of high-density data storage, bit-pattern media recording (BPMR) is considered a promising approach, as it can expand the data density to 4 Tb/in2. However, in high-density BPMR, bits or magnetic islands are very close to each other, leading to significant intertrack interference (ITI) from the cross-track direction and intersymbol interference (ISI) from the down-track direction. To minimize two-dimensional interference, including ITI and ISI, the serial detector method has been highly effective. However, in this method, the signal at the output of the first decoder is still a hard output. Therefore, we suggest methods to convert the output of the first detector into a soft output. Additionally, we have developed a new form of generalized partial response target to overcome the track mis-registration. The results show that our proposed methods apparently improve bit error rate performance.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Effective Generalized Partial Response Target and Serial Detector for Two-Dimensional Bit-Patterned Media Recording Channel Including Track Mis-Registration

Nguyen

Lee

2020

Applied Sciences

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“…In order to have a reliable channel model, 2-D interference and media noise need to be modeled. In [4], [5] ITI is modeled using the cross-track profile and along-track pulse response. However, when the read sensor is off track, the height and the width (or the PW50) of the along-track pulse response change.…”

Section: Introductionmentioning

confidence: 99%

Two-Dimensional Pulse Response and Media Noise Modeling for Bit-Patterned Media

2008

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In high density bit-patterned media (BPM), bits or magnetic islands are very close leading to significant inter-track interference (ITI) in addition to inter-symbol interference (ISI). Also, in BPM, major sources of media noise are the fluctuations in the location of the magnetic islands and fluctuations in the sizes of the magnetic islands. The location fluctuations can happen in both along-the-track and in cross-track directions. The size fluctuations affect both ISI and ITI. In order to obtain a more realistic channel model that includes the 2-D interference and the 2-D impact of media noise, we have developed a 2-D pulse response simulator for BPM. Utilizing the 2-D pulse response, we model the ITI and the media noise. Simulation results show that to achieve an acceptable bit error rate (BER), the location and size fluctuations should be smaller than 8% of the bit period at a density of 1.5 Tb in 2 .Index Terms-Bit-patterned media, media noise modeling, 2-D pulse response.

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“…To reduce the complexity of optimal 2-D detection, various suboptimal equalization and detection algorithms were proposed in [78]- [93]. In [78], the authors assumed symmetric ITI and proposed a modified VA to mitigate the effect of ITI. The readback signal is first passed through a 1-D equalizer and then detected by the modified Viterbi detector.…”

Section: Suboptimal Equalization and Detectionmentioning

confidence: 99%

“…In [79] and [80] [66]. Unlike the equalizers described in [9] and [78] in which only the main track was equalized to a 1-D target, this equalizer equalized all three tracks to a 2-D target. It has been shown that this joint-track equalizer performs close to the SSWA.…”

Section: Suboptimal Equalization and Detectionmentioning

confidence: 99%

Detection and decoding for two-dimensional interference channels

Yao¹

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In this thesis, we study the problem of communication over two-dimensional (2-D) interference channels which represent an important class of data storage and communication systems. The maximum-likelihood page detection (MLPD) for 2-D interference channels is firstly studied and the lower and upper performance bounds are derived. Although MLPD is computationally prohibitive and unachievable in practice, the performance bound of MLPD provides a benchmark of the optimal detection of 2-D interference channels. We also propose an approximated bounding method which can accurately predict the performance bound while greatly reducing the computational complexity. A joint iterative detection/decoding scheme (JIDDS) is proposed for 2-D interference system with low-density parity-check (LDPC) codes. The channel detector is composed of two constituent detectors that both adopt trellis-based maximum a posteriori probability (MAP) algorithms and they work in the down-track direction and cross-track direction, respectively. To achieve better performance, iterations are introduced between the two constituent detectors and among the constituent detectors with LDPC decoder. Simulation results show that the proposed scheme outperforms some existing algorithms. The better performance of JIDDS is achieved at the cost of higher computational complexity. A reduced-state channel detector is also proposed to save considerable complexity of the system but only degrade system performance marginally. In JIDDS, the channel detector and LDPC decoder work individually, which may result in some delays in detection/decoding. An appealing practical aspect of the decoding of LDPC codes is that it consists of many small, independent decoding functions (i.e., the variable nodes and check nodes) which can work in parallel. In order to make use of the low-delay advantage of LDPC codes, a joint message-passing decoding alvi gorithm (JMPDA) of LDPC codes and 2-D interference channels is proposed. The channel detector consists of many state-processing nodes which can be implemented in a completely parallel manner in conjunction with the decoding of LDPC codes. The performance of the JMPDA is almost the same as that of the JIDDS. An advantage of the JMPDA is its parallel implementation, leading to a high-speed decoder. Lastly, the extrinsic information transfer (EXIT) chart and density evolution (DE) are adopted in the analysis of the decoding of LDPC coded 2-D interference systems. The EXIT chart visualizes the evolution of mutual information between channel detection and LDPC decoding during the iterations. The effects of parameters to the decoding system are investigated by analyzing the EXIT curves. It is shown that given a good combination of parameters, the proposed algorithm will converge to the correct result. A graph representation of the JMPDA is explained. It is proved that the message-flow neighborhood of the JMPDA will be tree-like for a sufficiently long code length. It is further proved that the average performance of the JMPDA will concent...

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Modifying Viterbi Algorithm to Mitigate Intertrack Interference in Bit-Patterned Media

Cited by 55 publications

References 8 publications

Effective Generalized Partial Response Target and Serial Detector for Two-Dimensional Bit-Patterned Media Recording Channel Including Track Mis-Registration

Effective Generalized Partial Response Target and Serial Detector for Two-Dimensional Bit-Patterned Media Recording Channel Including Track Mis-Registration

Two-Dimensional Pulse Response and Media Noise Modeling for Bit-Patterned Media

Detection and decoding for two-dimensional interference channels

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