• Proceedings of the IEEK Conference
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• 2000.06a
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• pp.244-247
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• 2000

This paper deals with methods for partial response maximum-likelihood (PRML) detection and crosstalk cancellation. In accrodance with the demand for increased recording density, 20 gigabyte (Gbyte) digital versatile disk (DVD) ROM channel is considered. Channel is modelled to be close to real optical channel using DIFFRACT$\^$TM/. After comparing the spectral characteristics of various PR polynomials, P(D)=1＋D＋D$^2$＋D$^3$is proposed as a target PR. The performance of the system is illustrated under the condition that the readout signal is degraded by crosstalk, radial tilt and nonlinear distortions in optics. The experimental results show that crosstalk and nonlinear distortions degrade performance by about 2dB, respectively. We also show that when radial tilt is added to the crosstalk, the performance degradation assumes quite significant proprotions.

• Proceedings of the IEEK Conference
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• 2000.11a
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• pp.141-144
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• 2000

PRML (partial response maximum-likelihood) 과 FDTS/DF (fixed-delay tree search with decision feedback)는 기록 저장 시스템에서 준최적의 성능을 보임이 잘 알려져 있다. 그러나, 위와 같은 정보열 검출 기법은 피할 수 없는 복잡도 문제를 가지고 있다. 본 논문은 최소 run 길이 제한조건 d=2를 가진 광기록 채널을 위한 다양한 저복잡도 검출 기법을 다룬다. 우선, 결정 궤환 기법을 이용한 이산 정합 여파기 (discrete matched filter with decision feedback：DMF/DF)가 기존의 PRML로부터 유도된다. 유도된 시스템은 PRML보다 결정 궤환에 의한 성능 이득을 갖는다. 또한, 메트릭 계산을 사용하지 않는 저복잡도 FDTS/DF가 유도된다. 모의실험 결과에 의하면, 유도된 저복잡도 검출 기법들은 기록 밀도 S>=5.5에서 P(D)=1+D+D/sup 2/+D/sup 3/의 target을 갖는 PRML보다 우수한 성능을 보인다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.10A
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• pp.1000-1010
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• 2002

Partial response maximum-likelihood (PRML) and fixed-delay tree search with decision feedback (FDTS/DF) yield a sub-optimum performance in storage systems. However, they suffer from the inevitable complexity problems. this paper focuses on detection schemes to overcome the drawbacks of the sequence detections by exploiting minimum run-length d=2. It is expected that the proposed systems yield substantial reductions of both processing speed and receiver complexity. When combined with a decision feedback equalization (DFE), they prove to keep pace with the FDTS/DF with ${\tau}$=2 and even outperform the PR(1111)ML at normalized density S>5.6.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.7C
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• pp.581-586
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• 2010

The holographic data storage system stores multiple data pages by multiplexing. But the inter-page interference(IPI) caused by multiplexing reduces the intensity of the hologram. The simulation of the holographic storage systems has to consider the IPI. Therefore, we introduce a channel modeling that takes care of inter-page interference in the holographic data storage system. We simulate the performance of PRML detection on the hologrpahic data storage system with IPI modeling.

• Journal of the Korea Society of Computer and Information
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• v.13 no.4
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• pp.105-113
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• 2008

While the wireless sensor network has a strong point which does not have effect on whole activities of network even though neighboring sensor nods fail activities of some sensor nod or make some functions disappear by the characteristic of similar information detection, it has problems which is slowing down of wireless medium, transfer character with severe error, limited power supply, the impossibility of change by optional arrangement of sensor nods etc. This paper proposes PRML techniques which performs the fittest course searching process to reduce power consumption of entire nods while guarantees the scalability of network organizing sensor nods hierarchically. The proposed technique can scatter the load of cluster head by considering the connectivity with surplus energy of nod and reduce the frequency of communication among the nods. As a result of the analysis in comparison with LEACH-C and HEED technique, PRML technique get efficiency of average 6.4% in energy consuming respect of cluster head, efficiency of average 8% in entire energy consuming respect, and more efficiency of average 7.5% in other energy consuming distribution of network scalability than LEACH-C and HEED technique.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.22 no.11
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• pp.2439-2450
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• 1997

As recording densities increase in digital magnetic recording channels, the performances of digital detection techniques such as PRML and DFE degrade significantly due to nonlinear distortion in recording channels. The primary impediments for hgih-density recording are generally classified as nonlinear transition shift, which can be reduced substantially by the precompensation technique, and partial erasure which usually requires sophisticated nonlinear equalization techniques. In order to acheieve the highest density recording, accurate estimation of the parameters associated with these two noninear distortions is crucial. In this paper, a new estimation technique to distinguish these two different nonlinear effect using a proposed adaptive algorithm in time domain is presented. The effectiveness of the proposed adaptive approach to identify uniquely the nonlinear parameter with bias is demonstrated by computer simulation.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.6A
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• pp.562-567
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• 2002

Noise predictive maximum likelihood(NPML) detector embeds noise predictions/ whitening process in branch metric calculation of Viterbi detector and improves the reliability of branch metric computation. Therefore, PRML detector with a noise predictor achieves some performance improvement and has an advantage of low complexity. This paper shows that NP(1221)ML system through noise predictive PR-equalized signal has less complexity and better performance than high order PR(12321)ML system in high density perpendicular magnetic recording. The simulation results are evaluated using (1) random sequence and (2) run length limited (1,7) sequence, and they are applied to linear channel and nonlinear channel with normalized linear density $1.0{\leq}K_p{\leq}3.0$.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.3C
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• pp.336-342
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• 2003

Noise predictive maximum likelihood(NPML) detector embeds noise prediction/whitening process in branch metric calculation of Viterbi detector and improves the reliability of branch metric computation. Therefore, PRML detector with a noise predictor achieves some performance improvement and has an advantage of low complexity. This thesis random sequences are applied to linear channel. In perpendicular magnetic recording density KP=2.5, NP(121)ML and NP(1221)ML detection system which is based on a noise predictive PR-equalized signal are evaluated by the Performance through a computing simulation. Therefore, NPML systems are implemented and are verified by VHDL.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.8C
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• pp.569-574
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• 2008

Noise predictive maximum likelihood(NPML) detector embeds noise prediction! whitening process in the branch metric calculation of Viterbi detector and improves the reliability. In this paper, some high-density optical storage channels are examined, and appropriate NPML systems are designed for each channel.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.10B
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• pp.1732-1743
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• 2000

In this paper a fixed-delay trellis search with decision feedback (FDTrS/DF) for high-density DVD systems (4.7-15GB) is proposed and implemented with FPGA. The proposed FDTrS/DF is derived by transforming the binary tree search structure into trellis search structure implying that FDTrS/DF performs better than the singnal detection techniques based on tree search structure such as FDTS/DF and SSD/DF. Advantages of FDTrS/DF are significant reductions in hardware complexity due to the unique structure of FDTrS composed of only one trellis stage requiring no traceback procedure usually implemented in the Viterbi detector. Also in this paper the PDFS/DF and SSD/DF orginally proposed for high-density magnetic recording systems are modified for the DVD system and compared with the proposed FDTrS/DF. In order to increase speed in the FPGA implementation the pipelining technique and absolute branch metric (instead of square branch metric) are applied. The proposed FDTrS/DF is shown to provide the best performance among various signal detection techniques such as PRML, DFE, FDTS/DF and SSD/DF even with a small hardware complexity.