• 전자공학회논문지SC
• /
• 제46권6호
• /
• pp.58-64
• /
• 2009

디지털 방사선 영상은 첨가되는 잡음에 의해 영상이 흐려지고, 시스템 특성에 의해 왜곡된 영상을 얻게 된다. 이런 현상들은 보고자하는 영상의 본질을 보기 어렵게 한다. 왜곡된 영상을 복구하기 위해 웨이블릿 영역에서 다해상도 위너필터를 적용하였다. 다해상도 위너필터는 시스템 임펄스 응답과 잡음에 의해 변형된 프랙탈 신호의 복원을 위하여 Chen이 최초로 제안하였다. 본 논문에서는 Chen이 제안한 다해상도 위너필터를 2차원 영상 데이터에 대하여 적용하였다. 다해상도 위너필터와 다른 방법의 성능을 비교하기 위하여, 두 종류의 웨이블릿 필터들에 대하여 시스템 임펄스 응답과 잡음 전력의 특성에 따라 실험을 하였다. 첨가된 잡음 전력이 20-32 dB 일 때, 본 논문에서 제안한 방법의 신호 대 잡음비는 기존의 위너필터에 비해 0.5-2.0 dB 더 좋은 성능을 보였다.

• 한국정보통신학회논문지
• /
• 제12권1호
• /
• pp.164-171
• /
• 2008

디지털 통신에서는 전송 채널의 왜곡을 보상해 주는 적응 등화기가 필수적이다. 이러한 적응 등화기는 요구되는 비트 오율 (BER: Bit Error Rate)을 얻기 위해서 이동통신 시스템의 특성에 적합하고 최적의 성능을 가지는 적응 알고리즘이 필요하게 된다. 본 논문에서는 무선 이동 채널에서 성능이 우수한 잡음 예측 결정 궤환 등화기 (NPDFE: Noise-Predictive Decision Feedback Equalizer)를 제안한다. 제안된 NPDFE는 직교 위상 변조 (QPSK; Quadrature Phase Shift Keying) 방식을 사용하는 시스템에 대해 가산성 백색 가우스 잡음 (AWGN: Additive White Gaussian Noise)이 발생한다는 기본 가정하에 라이시안 페이딩, 유럽 표준 (ETSI: European Telecommunications Standards Institute) 페이딩, 그리고 레일리 페이딩 채널에서의 성능을 분석한다. 시뮬레이션에서 사용되는 등화기 구조는 선형 등화기(LE: Linear Equalizer), 결정 궤환 등화기 (DFE: Decision Feedback Equalizer), 그리고 제안된 NPDFE이다. 각 등화 알고리즘을 사용하는 QPSK 변조 방식의 성능 비교는 BER을 통하여 이루어진다.

• Journal of information and communication convergence engineering
• /
• 제1권3호
• /
• pp.119-122
• /
• 2003

In this paper presents equations which describe an average weighted spectrum of errors and average block error probabilities for noncoherent frequency shift keying (NCFSK) used in D-branch maximal ratio combining (MRC) diversity in independent very slow nonselective Nakagami fading channels. The average is formed over the instantaneous receiver signal to noise ratio (SNR) after combining. the analysis is limited to additive Gaussian noise.

• 한국방송∙미디어공학회:학술대회논문집
• /
• 한국방송∙미디어공학회 2019년도 추계학술대회
• /
• pp.119-121
• /
• 2019

부가적 백색 잡음 모델(additive white Gaussian noise, AWGN에서 학습된 깊은 신경만 (deep neural networks)을 이용한 잡음 제거기는 제거하려는 잡음이 AWGN인 경우에는 뛰어난 성능을 보이지만 실제 카메라 잡음에 대해서 잡음 제거를 시도하였을 때는 성능이 크게 저하된다. 본 논문은 U-Net 구조의 깊은 인공신경망 모델에 residual block을 결합함으로서 실제 카메라 영상에서 기존 알고리즘보다 뛰어난 성능을 지니는 신경망을 제안하다. 제안한 방법을 통해 Darmstadt Noise Dataset에서 PSNR과 SSIM 모두 CBDNet 대비 향상됨을 확인하였다.

• 대한전기학회논문지
• /
• 제39권4호
• /
• pp.380-385
• /
• 1990

This Paper presents a general algorithm for the parameter estimation of an antoregressive moving average process observed in additive white noise. The algorithm is based on the Gauss-Newton recursive prediction error method. For the parameter estimation, the output measurement is modelled as an innovation process using the spectral factorization, so that noise free RPE ARMA estimation can be used. Using apriori known properties leads to algorithm with smaller computation and better accuracy be the parsimony principle. Computer simulation examples show the effectiveness of the proposed algorithm.

• 대한전자공학회:학술대회논문집
• /
• 대한전자공학회 2002년도 ITC-CSCC -3
• /
• pp.1920-1923
• /
• 2002

This paper proposes an impulse response shortening algorithm applicable to decision feedback equalization of single carrier wideband signal. When he impulse response shortening methods for narrowband signaling are applied to single carrier wideband signals, they result in noise enhancement problem, significantly deterioriting the receiver performance. This problem can be alleviated by educing the eigenvalue spread ratio of the impulse response, which can be achieved by adding additive white noise with small variance to the impulse response of the channel. The performance of the proposed scheme is verified by computer simulation.

• 한국음향학회:학술대회논문집
• /
• 한국음향학회 1985년도 학술발표회 논문집
• /
• pp.87-94
• /
• 1985

In this paper, enhancement of speech corrupted by additive white or colored noise is stuided. The nuconstrained frequency-domain block least-mean-square (UFBLMS) adaptation algorithm and its frequency-weighted version are newly applied to speech enhancement. For enhancement of speech degraded by white noise, the performance of the UFBLMS algorithm is superior to the spectral subtraction method or Wiener filtering technique by more than 3 dB in segmented frequency-weighted signal-to-noise ratio(FWSNERSEG) when SNR of speech is in the range of 0 to 10 dB. As for enhancement of noisy speech corrupted by colored noise, the UFBLMS algorithm is superior to that of the spectral subtraction method by about 3 to 5 dB in FWSNRSEG. Also, it yields better performance by about 2 dB in FWSNR and FWSNRSEG than that of time-domain least-mean-square (TLMS) adaptive prediction filter(APF). In view of the computational complexity and performance improvement in speech quality and intelligibility, the frequency-weighted UFBLMS algorithm appears to yield the best performance among various algorithms in enhancing noisy speech corrupted by white or colored noise.

• 대한음성학회:학술대회논문집
• /
• 대한음성학회 2002년도 11월 학술대회지
• /
• pp.179-182
• /
• 2002

The development of noise robust speech processing systems is becoming increasingly important as speech technology is currently widely applied in real world applications. Recently, to resolve such a noise problem, adaptive noise canceller(ANC) is frequently used, which is based upon adaptive filters. The adaptive recursive filters perform better than adaptive non-recursive filters due to the added poles, but the stability may be severely threatened. But these problems of adaptive recursive filters was solved by ACHARF algorithm. This paper presents a method which combines speaker verification system with ANC(Adaptive Noise Canceller) using the ACHARF algorithm. In the front-end stage, ANC is adopted to suppress the additive noise imposed on the speech signal. The results show that the performance of speaker verification system becomes better than before.

• 대한원격탐사학회:학술대회논문집
• /
• 대한원격탐사학회 2007년도 춘계학술대회 논문집
• /
• pp.126-129
• /
• 2007

In this paper, an iterative MAP approach using a Bayesian model based on the lognormal distribution for image intensity and a GRF for image texture is proposed for despeckling the SAR images that are corrupted by multiplicative speckle noise. When the image intensity is logarithmically transformed, the speckle noise is approximately Gaussian additive noise, and it tends to a normal probability much faster than the intensity distribution. The MRF is incorporated into digital image analysis by viewing pixel type s as states of molecules in a lattice-like physical system defined on a GRF. Because of the MRFGRF equivalence, the assignment of an energy function to the physical system determines its Gibbs measure, which is used to model molecular mteractions. The proposed adaptive iterative method was evaluated using simulation data generated by the Monte Carlo method. In the extensive experiments of this study, the proposed method demonstrated the capability to relax speckle noise and estimate noise-free intensity.

• 전자공학회논문지B
• /
• 제32B권1호
• /
• pp.85-95
• /
• 1995

The error intensity models for the ML estimation of a signal parameter have been developed in a companion paper [1]. While the methods described in [1] are applicable to any estimation problem with continuous parameters, our main application in this paper is the time delay estimation, and comparisons among the models derived in [1] (i.e. LC, LM, and ALM models)have been made. We first consider the case where only additive Gaussian noise is involved, and then the shot noise environment where coherent impulsive noise is also involved in addition to the Gaussian noise. We compare the models in terms of the probability of error, MSE(Mean Squared Error), and the computational complexity, which are the most important performance criteria in the analysis of parameter estimation. In conclusion, the ALM model turned out to be the most adequate model of all from the viewpoints of the criteria mentioned above.