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Equalization of 8-VSB Signals using Complex-Valued Decision Feedback Filter
Wonzoo Chung(鄭原周) 대한전기학회 2006 전기학회논문지 D Vol.55 No.7
In this paper, we present an equalization scheme for 8-VSB signals for the ATSC DTV system. We propose a complex feedback filter and complex feedback sample generator for DFE to equalize 8-VSB signals in order to efficiently remove multipath distortions causing leakages from the qudrature component. We show that the proposed structure outperforms the conventional DFE used for the digital VSB which uses a real-valued feedback filter with real-valued decisions.
정원주(Wonzoo Chung),이성환(Seong-Whan Lee) 한국정보과학회 2016 정보과학회논문지 Vol.43 No.7
본고에서는 양자역학 기반의 기계학습인 양자 기계학습의 현황과 전망을 조망하고자 한다. 양자역학 기반의 양자컴퓨팅이 보여준 혁신적인 계산속도 개선에 힘입어 기계학습 분야에 양자컴퓨팅 알고리즘을 적용하는 연구는 빅데이터 시대의 도래에 따라 최근 집중적인 관심을 받고 있다. 고전적인 기계학습 알고리즘들에 양자컴퓨팅을 접목하여 획기적인 속도개선을 가능하게 하는 알고리즘 연구들과 최초의 상용 양자컴퓨터로 화제가 되고 있는 양자 담금질 알고리즘 등을 중심으로 양자 기계학습의 최신동향과 가능성을 살펴보고자 한다. This paper presents an overview of the emerging field of quantum machine learning which promises an innovative expedited performance of current classical machine learning algorithms by applying quantum theory. The approaches and technical details of recently developed quantum machine learning algorithms that have been able to substantially accelerate existing classical machine learning algorithms are presented. In addition, the quantum annealing algorithm behind the first commercial quantum computer is also discussed.
Channel Estimation Methods Based on Volterra Kernels for MLSD in Optical Communication Systems
IEEE 2010 Photonics Technology Letters Vol.22 No.4
<P>Maximum likelihood sequence detection (MLSD) is the most effective electrical domain equalization scheme for mitigating dispersive optical channel impairments such as chromatic dispersion or polarization-mode dispersion. Parameter estimation for MLSD is not straightforward in optical communication systems due to the square-law nature of photodiodes. We propose a simple and efficient channel parameter estimation scheme for MLSD based on Volterra kernel modeling of the nonlinear distortion of the electrical postdetection signals.</P>
Jeon, Hyeonmu,Chung, Yongseek,Chung, Wonzoo,Kim, Jongmann,Yang, Hoongee The Korean Institute of Electrical Engineers 2018 Journal of Electrical Engineering & Technology Vol.13 No.1
Reliable detection and parameter estimation of a radar cross section(RCS) fluctuating target have been known as a difficult task. To reduce the effect of RCS fluctuation, various diversity techniques have been considered. This paper presents a new method for synthesizing a covariance matrix applicable to a coherent multi-input multi-output(MIMO) radar with frequency diversity. It is achieved by efficiently combining covariance matrices corresponding to different carrier frequencies such that the signal-to-noise ratio(SNR) in the combined covariance matrix is maximized. The value of a synthesized covariance matrix is assessed by examining the phase curves of its entries and the improvement on direction of arrival(DOA) estimation.
Non-Data-Aided Phase Noise Suppression Scheme for CO-OFDM Systems
Youngsun Ha,Wonzoo Chung IEEE 2013 Photonics Technology Letters Vol.25 No.17
<P>We propose a non-data-aided phase noise compensation technique that overcomes the limitation of the zero-overhead decision-directed (DD) phase noise suppression method in high-order constellations for coherent optical orthogonal frequency division multiplexing (CO-OFDM) systems. The proposed technique consists of two equalization stages. First, a blind adaptive phase offset recovery scheme based on high-order statics, called the dispersion minimization de-rotator, is applied to subcarrier symbols to achieve rough correction of the common phase error because of phase noise. Second, the conventional DD phase noise correction scheme is used to remove the residual common phase error. The proposed method effectively compensates phase noise without the help of pilot signals, especially for high-order constellation CO-OFDM systems, as confirmed by our simulation results.</P>
Enhancement of Few-shot Image Classification Using Eigenimages
Jonghyun Ko,Wonzoo Chung 제어·로봇·시스템학회 2023 International Journal of Control, Automation, and Vol.21 No.12
In this paper, we propose an auxiliary loss function called an eigen loss to reduce the overfitting of fewshot learning algorithms. The proposed loss function predicts the class of unlabeled query images by measuring the similarity between the query image and reconstructed image constructed from the eigenimages of the support data. The eigen loss is used in a linearly combined form with the existing loss function of few-shot learning models. Experimental results of the eigen loss applied to representative few-shot learning models on widely used datasets (i.e., MiniImageNet, CUB, and TieredImageNet) show that the proposed method yields notable improvements in terms of classification accuracy.
Reduced-State MLSD Based on Volterra Kernels for Square-Law Detected Multipath Channels
( Youngsun Ha ),( Wonzoo Chung ) 한국인터넷정보학회 2011 KSII Transactions on Internet and Information Syst Vol.5 No.12
We propose a novel reduced-state maximum-likelihood sequence detection (MLSD) structure using the Viterbi algorithm based on the second-order Volterra kernel modeling nonlinear distortion due to square law detection of multipath channels commonly occurring in chromatic dispersion (CD) or polarization mode dispersion (PMD) in optical communication systems. While all existing MLSD methods for square-law detection receivers are based on direct computation of branch metrics, the proposed algorithm provides an efficient and structured way to implement reduced-state MLSD with almost the same complexity of a MLSD for linear channels. As a result, the proposed algorithm reduces the number of parameters to be estimated and the complexity of computation.
분산 다중 전자전 센서를 이용한 ESPRIT 기반 비등간격 선형배열 MIMO 레이다의 암맹 직교신호 분리 기법
여광구(Kwanggoo Yeo),정원주(Wonzoo Chung) 한국전자파학회 2018 한국전자파학회논문지 Vol.29 No.11
본 논문에서는 안테나 배열 간격이 등간격 선형배열(uniform linear array)이 아닌 비등간격 선형배열인 MIMO(Multiple-Input Multiple-Output) 레이다의 직교신호 분리에 대하여 논의한다. 다중의 전파탐지기를 이용하여 얻은 신호를 기반으로 전파탐지기 배치를 통하여 새로운 rotational invariance 구조를 부여하여 ESPRIT 알고리즘을 이용할 수 있게 한다. 이를 통하여 수신신호로부터 직접 MIMO 레이다의 직교신호를 간단한 연산으로 암맹적으로 분리하는 방법을 제시한다. 추정된 직교신호를 이용하여 차후 MIMO 레이다의 무력화 혹은 기만에 활용할 수 있도록 한다. In this paper, we propose a blind estimation scheme for the antenna spacing of nonuniform linear array MIMO radar using distributed electronic sensors based on ESPRIT. We present a blind method to separate orthogonal waveforms of a MIMO radar based on the antenna spacing estimation. The estimated orthogonal waveforms of a MIMO radar can be used for disabling opponent MIMO radars.
SC-FDE에서 주파수 도메인 파일럿 시스템의 시간도메인 접근
하영선(YoungSun Ha),정원주(WonZoo Chung) 대한전기학회 2010 정보 및 제어 심포지엄 논문집 Vol.2010 No.10
이 논문에서는 SC-FDE 시스템에서 최소한의 시간 도메인 트레이닝 신호를 사용하여 보다 효율적인 주파수 도메인 파일럿 신호체계 구성을 제안하고자 한다. 기존에는 시간 도메인의 트레이닝 신호를 통해 추정된 채널을 주파수 도메인 채널등화에 이용하거나 혹은 주파수 도메인에서 데이터 심볼을 등간격으로 소거한 뒤 파일럿 톤을 삽입하는 방법들이 있었다. 하지만 이러한 방법으로는 Data Rate이 낮아지거나 혹은 소거된 데이터 심볼로 인한 ISI(Inter Symbol Inteference)가 발생하게 된다. 이러한 문제점을 극복하기 위해 본 논문에서는 최소한의 시간 도메인 트레이닝 신호를 활용하여 소거된 주파수 도메인 데이터 심볼을 추정함으로써 ISI를 감소시키는 파일럿 신호체계 구성을 제안한다.