• Journal of the Institute of Electronics Engineers of Korea TC
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• v.49 no.1
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• pp.11-18
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• 2012

In this paper, we propose a novel equal-gain differential precoding scheme utilizing temporal correlation of channels. The conventional differential precoding schemes only quantize a part of channel space not the whole channel space, so that it virtually increases codebook size which enhances the system capacity. But the conventional differential schemes increase peak-to-average power ratio (PAPR) without preserving equal-gain transmission. This paper proposes the design method of equal-gain differential precoding scheme and analyzes the performances of the proposed equal-gain precoding scheme. Monte-Carlo simulations verify that the proposed scheme has an advantage of 1dB to obtain the same system capacity with the same amount of feedback information compared with the conventional LTE schemes, with showing very low PAPR property.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.23 no.10
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• pp.1180-1187
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• 2012

In this paper, joint transmission space division multiple access(JT-SDMA) scheme is proposed to mitigate inter-cell interference(ICI) in cooperative wireless communications system with limited feedback. We propose a systematic design method for a codebook consisting of a finite number of unitary matrices suitable for network multiple-input multiple-output( MIMO) channel characteristics. A centralized cluster scheduling scheme is proposed to both mitigate ICI and maximizes multiuser diversity gain with limited feedback. It is shown that the proposed JT-SDMA scheme outperforms a existing coordinated SDMA scheme even in wireless network environments where sufficient multiuser diversity order can not be provided through efficient ICI mitigation.

• Nuclear Engineering and Technology
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• v.27 no.4
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• pp.518-531
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• 1995

A study has been Peformed to investigate the thermal margin increase by replacing the single-channel analysis model with a multichannel analysis model. h new critical heat flux(CHF) correlation, which is applicable to a 17$\times$17 Korean Fuel Assembly(KOFA)-loaded core, was developed on the basis of the local conditions predicted by the subchannel analysis code, TORC. The hot sub-channel analysis was carried out by using one-stage analysis methodology with a prescribed nodal layout of the core. The result of the analysis shooed that more than 5％ of the thermal margin can be recovered by introducing the TORC/KRB-1 system(multichannel analysis model) instead of the PUMA/ERB-2 system(single-channel anal)sis model). The thermal margin increase was attributed not only to the effect of the local thermal hydraulic conditions in the hot subchannel predicted by the code, but also to the effect of the characteristics of the CHF correlation.

• Proceedings of the Korea Society of Information Technology Applications Conference
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• 2002.11a
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• pp.407-411
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• 2002

Ternary sequences are digital codes consisting of discrete values -1, 0, and 1 only. They are advantageous in that the correlation can be carried out using additions only. Also, they feature an ideal circular autocorrelation function, but in channel characterization tasks, the usual requirement is that the linear autocorrelation function be ideal, i.e., a Kronecker delta function. In this article, we consider two approaches to improving their linear autocorrelation or crosscorrelation properties: one is an inverse filtering method with thresholding, and the other is a singular value decomposition (SVD) method. Both methods are simulated under noisy circumstances. The inverse filtering method resulted in an improvement in peak sidelobe level of about 11 dB at an SNR of 30 dB, and the SVD method showed similar performances, albeit more sensitive to noise depending on the singular value selection strategy.

• Proceedings of the Korea Society for Industrial Systems Conference
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• 2002.11a
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• pp.407-411
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• 2002

Ternary sequences are digital codes consisting of discrete values -1, 0, and 1 only. They are advantageous in that the correlation can be carried out using additions only Also, they feature an ideal circular autocorrelation function, but in channel characterization tasks, the usual requirement is that the linear autocorrelation function be ideal, i.e., a Kronecker delta function. In this article, we consider two approaches to improving their linear autocorrelation or crosscorrelation properties: one is an inverse filtering method with theresholding and the other is a singular value decomposition (SVD) method. Both methods are simulated under noisy circumstances. The inverse filtering method resulted in an improvement in peak sidelobe level of about 1㏈ at an SNR of 30㏈, and the SVD method showed similar performances, albeit more sensitive to noise depending on the singular value selection strategy.

• Journal of the Korean Institute of Telematics and Electronics B
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• v.33B no.1
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• pp.161-169
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• 1996

This paper presents a new search region prediction method using vector quantization for the motion estimation. We find motion vectors using the full search BMA from two successive frame images first. Then the motion vectors are used for training a codebook. The trained codebook is the predicted search region. We used the unsupervised neural network for VQ encoding and codebook design. A major advantage of formulating VQ as neural networks is that the large number of adaptive training algorithm that are used for neural networks can be applied to VQ. The proposed method reduces the computation and reduce the bits required to represent the motion vectors because of the smaller search points. The computer simulation results show the increased PSNR as compared with the other block matching algorithms.

• The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
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• v.6 no.1
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• pp.66-76
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• 1995

In this paper, the error rate performance of DS/SSMA system in multipath fading channel is calculated by computer simulation. At first, the multipath fading channel is modeled with TDL(Tap Delay Line) model. The characteristics of channels, including multipath fading effects and error pattern, are examined by doppler frequency and signal bandwidth, and time spread variation. Using the multipath fading channel model, the error rateperformance of block code and convolutional code is compared, thus the coding sys- tem is applied to the DS / SSMA system. The BER results of DS / SSMA system show that the proposed receiver gives about 2~3[dB] improve- ment compared with the conventional receiver.

• Proceedings of the Korea Information Processing Society Conference
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• 2012.04a
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• pp.236-238
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• 2012

본 논문에서는 클라우드 기반의 하이브리드 어플리케이션 개발환경을 제안한다. 최근 다양한 모바일 플랫폼이 등장하고 있다. 이에 동일한 컨텐츠를 각 플랫폼 환경에 맞춰 별도로 제작해야되는 비용 증가 문제와 플랫폼 별 소스코드 유지보수에서 발생하는 소스코드 간 비일관성 문제가 발생하였다. 따라서 이기종 모바일 플랫폼에서 동시에 구동이 가능한 어플리케이션 개발 기술이 요구되었고 이에 모바일 플랫폼에 상관없이 개발 및 배포가 자유로운 환경인 하이브리드 어플리케이션 개발환경을 제안한다. 또한 개발 환경을 확장해 클라우드 기반의 모바일 개발환경을 제안하고 이를 시험적으로 구현한 지능형 응용 스튜디오를 소개한다.

• Proceedings of the Korea Information Processing Society Conference
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• 2010.04a
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• pp.22-25
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• 2010

재구성형 프로세서는 파워를 적게 사용하면서도 높은 성능을 낼 수 있는 프로세서이다. 재구성형 프로세서는 하드웨어에 최대한 많은 계산 자원을 넣으면서도 구조를 최대한 간단하게 하여 저전력 소모와 고성능을 동시에 추구하였다. 하지만 구조를 최대한 간단히 하는 과정에서 프로그램의 수행을 관리하는 많은 하드웨어 로직이 빠지게 되었는데, 이 부분은 컴파일러에서 코드를 생성할 때 스케쥴링과 수행 순서까지 정해지도록 소프트웨어적 관점에서 처리하기로 하였다. 이를 사용하기 위해 컴파일러는 입력된 프로그램을 분석하고 재구성형 프로세서에서 수행될 수 있는 형태로 코드를 각 계산자원에 매핑하는 작업을 수행해 주어야 한다. 재구성형 프로세서의 레지스터는 이 매핑 과정에서 데이터의 전달을 위해서 주로 사용되게 된다. 이 논문에서는 다양한 멀티미디어 응용 프로그램을 사용하여 멀티미디어 환경에서 재구성형 프로세서가 사용될 때 레지스터 개수가 성능에 미치는 영향을 제시한다.

• The KIPS Transactions:PartB
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• v.10B no.4
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• pp.367-372
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• 2003

The existing watermarking techniques for copyright protection of a digital image are fragile in geometric distortion and it is hard to detect whether it was manipulated artificially. In this paper, we proposed the new copyright protection system that can authorize a digital mage and :an embed or extract a robust watermark in a artificial manipulation in order to solve these problems. In a watermarking part, the proposed a watermarking technique embeds a watermark in a phase component after a Complex Wavelet Transform (CWT) with an original image, and a watermark is extracted from an watermarked image by stages. A copyright about an image can be insisted on than a threshold after comparing a correlation of an original watermark with an extracted watermark if large. In an authentication part of a digital image, EZW (Embedded Zerotree Wavelet) is used, and an authentication cord of an watermarked image is generated. An authentication code of an image to have been distribute to is compared with a generated authentication cord, and artificial operation isn´t than a threshold if large. The proposed copyright protection system through performance evaluation display that it was robust in geometric distortion and a artificial operation was able to be detected.