• Proceedings of the IEEK Conference
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• 1998.10a
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• pp.775-778
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• 1998

근래에 들어 컴퓨터 기술은 멀티미디어 기수의 발달과 더불어 그에 따른 데이터량의 증가로 인해 데이터를 처리, 전송, 저장하는 모든 부문에서의 고속, 대용량화를 요구하고 있다. 이 중에서 특히 저장장치 부문은 응용 프로그램이 대형화되고 멀티미디어화에 따른 데이터량이 크게 증가하는 추세에 있기 때문에 지속적인 용량 증가가 요구되고 있다. 이런 상황에서 주목을 받고 있는 것이 신호처리 방식을 개선하여 저장장치의 기록 밀도를 향상시키는 기술의 하나인 partial response maximum likelihood (PRML) 기술이다. PRML 방식은 HDD 나 광 디스크로부터 데이터를 읽어낼때의 신호처리 기술 중의 ㅎ나로 신호간 간섭을 허용하여 데이터 속도를 증가시키고, 신호를 재생할 때 신호간 간섭을 보상하여 원래 신호를 복원해 내는 기술이다. 이를 이용하면 기존의 기록방식에 비해 기록밀도를 20-50% 정도 높일 수 있다.〔1〕〔2〕

• Proceedings of the IEEK Conference
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• 2000.09a
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• pp.255-258
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• 2000

본 논문에서는 효율적인 면적의 저전력 FIR 필터를 제안한다. 제안된 필터는 6 비트 8 탭의 구조를 갖는PRML(Partial-Response Maximum Likelihood) 디스크드라이브 read channel용 FIR 필터이다 제안된 구조는 병렬연산 구조를 채택하고 있으며 네 단의 파이프라인 구조를 가지고 있다. 곱셈을 위하여 부스 알고리즘이 사용되며 압축기를 이용하여 덧셈을 수행한다. 저전력을 위해 CMOS 패스 트랜지스터를 사용하였으며 면적을 줄이기 위해 single-rail 로직을 사용하였다 제안된 구조를 0.65㎛ CMOS 공정을 이용하여 설계하였으며1.88 × 1.38㎟의 면적을 차지하였고 HSPICE 시뮬레이션 결과 3.3V의 공급전압에서 100㎒로 동작시 120㎽의 전력을 소모한다. 제안된 구조는 기존의 구조들에 비해 약 11%의 전력이 감소했으며 약 33%의 면적이 감소하였다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.4C
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• pp.299-304
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• 2008

For perpendicular magnetic recording channels, it is hard to expect improving the performance by using the PRML or NPML. Hence, we exploit LDPC code to improve the performance. In this paper, we examine a single message-passing detector/decoder matched to the combination of a perpendicular magnetic recording channel detector and an LDPC code decoder. We examine the performance of channel iteration with joint LDPC code on perpendicular magnetic recording channel, and simplify the complexity of the message-passing detector algorithm.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.1B
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• pp.66-78
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• 2002

In this paper, we propose a new symbol offset estimation technique for an orthogonal frequency-division multiplexing (OFDM)-based wireless LAN. When both inter-symbol interference (ISI) and inter-channel interference (ICI) do not exist in an OFDM symbol, symbol offsets cause circular shifts in the estimated channel impulse response (CIR) by the amount of symbol offset. Also, the power delay profile of a typical multipath wireless channel can be modeled by exponentially decaying function, and most energy of multipath channel is concentrated at the beginning part of the CIR. Based on these properties, the proposed symbol offset estimation technique estimates the CIR, which is circularly shifted by the amount of symbol offset, and then calculates the partial mean power from the estimated impulse response by using a moving window with a finite length. And, symbol offset can be estimated from the index of a moving window having the maximal partial mean power. The proposed technique can reduce noise effect in the process of the CIR estimation, and remove ISI and ICI using repetitive training symbol structure in time-domain for minimum training overhead. The performances of the proposed symbol offset estimation technique in typical indoor channels are demonstrated by computer simulation.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.5 no.5
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• pp.454-457
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• 2004

Partial response maximum likelihood (PRML) is a powerful and indispensable detection scheme for perpendicular magnetic recording channels. The proposed method is a low complexity detection scheme which is related to the PRML system. The simulation results show that PR(1,2,3,4,3,2,1)ML and PR(l,2,3,3,2,1)ML using modulation encoding with R=2/3 have the most improved performance at K=3,4. However, in the case of K=3, R=2/3 PR(1,1,1,1)ML effectively reduces the complexity compared to PR(1,2,3,3,2,1), but it has L5dB performance degradation at most. In the case of K=4, R=l PR(1,2,2,1)ML has very low complexity compared to R=2/3 PR(l,2,3,4,3,2,1)ML. but it has about 2dB performance degradation at most.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.41 no.9
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• pp.115-124
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• 2004

This paper proposes a high efficient and low power FIR filter chip for partial-response maximum likelihood (PRML) disk drive read channels; it is a 6-bit, 8-tap digital FIR filter. The proposed filter employs a parallel processing architecture and consists of 4 pipeline stages. It uses the modified Booth algorithm for multiplication and compressor logic for addition. CMOS pass-transistor logic is used for low power consumption and single-rail logic is used to reduce the chip area. The proposed filter is actually implemented and the chip dissipates 120mV at 100MHz, uses a 3.3V power supply and occupies 1.88 ${\times}$ 1.38 $\textrm{mm}^2$. The implemented filter requires approximately 11.7% less power compared with the existing architectures that use the similar technology.

• Journal of Distribution Science
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• v.21 no.3
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• pp.83-92
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• 2023

Purpose: An omnichannel strategy creates a consistent brand image and customer experience across all channels, making it easier for customers to interact with a business and share information. This research aimed to investigated the relationship between consumers' information-sharing intention and their omnichannel experiences. Research design, data, and methodology: Through an online survey conducted in Vietnam, the study obtained 915 responses. The study used Partial Least Square Structural Equation Modeling (PLS-SEM) to analyze research data and confirm proposed research hypotheses. Results: Research results indicated that information-sharing intention is affected by both online and offline customer experience, and at the same time, the study also confirmed that omnichannel's three characteristics (integration, individualization, interaction) positively impact on customer experience. Conclusions: From the research result, businesses may boost consumer trust and loyalty with the help of an omnichannel approach, which in turn increases customers' propensity to provide personally identifying information to the firm. One way to do this is to facilitate information exchange by delivering customized and relevant offers. Furthermore, companies show consumers the benefit of providing their data by utilizing it to enhance the customer experience.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.4C
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• pp.413-423
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• 2003

The CMA algorithmis most widely investigated blind algorithm and the most widely used one in practice. But, since nonlinear CM cost function have not closed form solution about the optimum weight. There have been difficultiesto analyze the CMA equalizer's theoretical performance. Recently, Zeng presents the notable theoretical resultabout the MSE of CM-minimizing estimators for the FIR linear channel in the presence of AWGN. Through this method, It wouldbe possible to campare the theoretical performance between CMA and Wiener equalizer in terms of MSE. In this paper, based on Zeng's method, we first calculate the theoretical MSE bound of CMA equalizer in partial response channel which is widely used in HDD, digital VCR such as high-density digital recording.playback systems. We confirmedthis result withthe computer simulation. Except this, we also performedthe theoretical and simulation analysis about the modified CMA equalizer, which was proposed to improve the performance of CMA equalizer in partial response channel. Finally, we compare and evaluate the performance analysis results between CMA and Modified CMA equalizer.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.3C
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• pp.77-82
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• 2005

Partial response maximum likelihood (PRML) detection using the Viterbi algorithm involves the calculation of likelihood metrics that determine the most likely sequence of decoded data. In general, it is assumed that branches at each node in the trellis diagram have same probabilities. If modulation code with minimum and maximum run-length constraints is used, the occurrence ratio (Ro) of each particular pattern is different, and therefore the assumption is not true. We present a calculation scheme of the likelihood metrics for the PRML detection using the occurrence ratio. In simulation, we have tested the two (1,7) run-length-limited codes and calculated the occurrence ratios as the orders of PR targets are changed. We can identify that the PRML detections using the occurrence ratio provide more than about 0.5dB gain compared to conventional PRML detections at 10/sup -5/ BER in high-density magnetic recording and optical recording channels.

• Journal of Chest Surgery
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• v.34 no.9
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• pp.704-710
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• 2001

Background: Extracorporeal circulation using pump-oxygenator is an inevitable process to keep vital sign during cardiac arrest for open heart surgery. However, the diversion of blood through nonendothelialized channels appears to stimulate inflammatory response, and leukocyte activation may lead to cardiopulmonary edema. Our study evaluated the effect of leukocyte-induced cardiopulmonary edema using three different pump-oxygenator priming solutions; non-hemic crystalloid solution ; leukocyte-depleted homologous blood; non leukocyte-depleted homologous blood in priming solutions. Material and Method: Each different priming solution was used on five dogs, and the effect of leukocyte-induced cardiopulmonary edema during cardiopulmonary bypass(CPB) was evaluated. For each dog after 2 hours of exracorporeal circulation and another 4 hours of post-pump period, the dog was sacrificed and its heart and lung tissues were obtained for measuring Wet/Dry ratio. Arterial $O_2$partial pressure(PaO$_2$) and $CO_2$partial pressure(Pa$CO_2$) were checked. For the evaluation of ventilatory function, $CO_2$partial pressure difference between arterial blood (Pa$CO_2$) and exhaled air(Et$CO_2$) was measured. Result: 1. No significant difference was seen in arterial PaO$_2$and Pa$CO_2$among groups. 2. Ventilatory function evaluated by Pa$CO_2$and Et$CO_2$showed no significant difference between non-hemic and blood-mixed priming solution (P<0.05). 3. Cardiac and lung Wet/Dry ratios were remarkedly lower in the leukocyte-depleted group. There was no significant difference between the non-hemic and blood-mixed groups. Conclusion: Based upon this result, we concluded that the leukocyte depletion from homologous blood of CPB priming solution has a beneficial effect in reducing cardiopulmonary edema compared with non leukocyte-depleted or crystalloid priming solutions.