• Proceedings of the Korean Information Science Society Conference
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• 2002.10c
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• pp.535-537
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• 2002

본 논문에서는 HVS을 이용하여 웨이브렛기반 이미지 워터마킹 기법을 제안한다. 웨이브렛 변환 된 각 밴드 중 최고 저주파 밴드에 인접한 3개의 밴드를 선택하여 각 밴드에 워터마크를 반복적으로 삽입하여 견고성을 높였다. 또한 밴드 안의 모든 계수 값에 워터마크를 삽입하지 않고 선택적으로 삽입함으로써 비가시성을 고려하였다. 저주파 영역에 워터마크를 삽입함으로서 가우시안 노이즈나 JPEG, 잘라내기 등 여러 공격모델에 대해 견고성을 잘 보여주고 있다.

• Journal of Korea Multimedia Society
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• v.16 no.9
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• pp.1005-1017
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• 2013

Voice activity detection is very important process that voice activity separated form noisy speech signal for speech enhance. Over the past few years, many studies have been made on voice activity detection, but it has poor performance in low signal to noise ratio environment or fickle noise such as car noise. In this paper, it proposed new voice activity detection algorithm using ensemble variance based on wavelet band entropy and soft thresholding method. We conduct a survey in a lot of signal to noise ratio environment of car noise to evaluate performance of the proposed algorithm and confirmed performance of the proposed algorithm.

• Proceedings of the Korean Information Science Society Conference
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• 2002.04a
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• pp.877-879
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• 2002

본 논문에서는 HVS을 이용한 웨이브렛 패킷 기반 이미지 워터마킹 기법을 제안한다. 이미지를 주파수/공간 도메인 상에서 세부적으로 분해하기 위해 웨이브렛 패킷 분해방법을 선택했고 워터마크 삽입 후 사람 눈에 안보일 수 있도록 MTF를 참고하여 워터마크를 삽입하였다. 모든 서브 밴드에 랜덤 가우시안 백터에 의해 생성된 1000개의 워터마크를 골고루 삽입함으로써 견고성측면을 강화하였다. 실험 결과는 이런 비가시성과 가우시안 노이즈나 JPEG, 잘라내기등 여러 공격모델에 대해 견고성을 잘 보여주고 있다.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.37 no.6
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• pp.48-59
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• 2000

Eigendecomposition based direction-of-arrival(DOA) estimation algorithm such as MUSIC(multiple signal classification) is known to perform well and provide high resolution in white noise environment. However, its performance degrades severely when the noise process is not white. In this paper we consider the DOA estimation problem in a colored noise environment as a problem of extracting periodic signals from noise, and we take the problem to the wavelet domain. Covariance matrix of multiscale components which are obtained by taking wavelet decomposition on the noise has a special structure which can be approximated with a banded sparse matrix. Compared with noise the correlation between multiscale components of narrowband signal decays slowly, hence the covariance matrix does not have a banded structure. Based on this fact we propose a DOA estimation algorithm that transforms the covariance matrix into wavelet domain and removes noise components located in specific bands. Simulations have been carried out to analyze the proposed algorithm in colored noise processes with various correlation properties.

• The Journal of Information Technology
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• v.2 no.2
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• pp.127-138
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• 1999

The wavelet transform is widely used in signal processing application. In this paper, a wavelet domain adaptive algorithm(WPTNLMS) is derived and its performances are evaluated in non-stationary environment. Where the input signals are decomposed by the wavelet packet transform for the multi-resolution adaptive processing. And the NLMS is used as an adaptive algorithm in wavelet domain. The proposed technique is applied to noise cancellation of the Doppler signal which is added with white Gaussian noise.

• Proceedings of the Korea Institute of Convergence Signal Processing
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• 2000.08a
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• pp.21-24
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• 2000

Fractional Brownian motion(fBm)은 long-term persistence 특성을 가진 자연 현상, 1/f 잡음, 깊이가 낮은 해저에서의 배경음향잡음 등을 모델링하는데 많이 사용된다. 이 fBm은 nonstationary 유색잡음이다. 이러한 유색잡음 환경 하에서 신호를 검출하기 위한 한 방법은 Fredholm 적분방정식의 해를 구하는 것이다. 이 방정식을 이산화 하면 잡음의 공분산 행렬의 역행렬이 포함되어 계산량이 많다 본 논문에서는 fBm 잡음의 공분산 행렬을 웨이브렛 변환하여 얻어지는 행렬, 즉 fBm의 멀티스케일 성분들의 공분산행렬은 밴드화된 블록들로 근사화할 수 있다는 성질을 이용하여 적은 계산량으로 신호를 검출하는 알고리즘을 제안한다.

• Proceedings of the Korean Information Science Society Conference
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• 1998.10c
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• pp.523-525
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• 1998

웨이브렛 변환을 사용한 영상은 인간의 시각체계(HVS)에 적적한 양자화 및 부호화를 위한 계층적 구조를 제공한다. 인간의 시각이 민감하게 감지하는 부분을 더 정확하게 부호화 하고, 그렇지 못한 부분에서는 적절한 정보의 손실을 허용하는 원리를 이상적으로 적용할 수 있다. 이런 웨이브렛 변환영상의 통계적 특성을 이용한 제로트리 부호화 기법은 중요한 영상계수를 선별하여 영상전체에서 의미있는 계수를 순서대로 부호화 함으로써 매입 파일(Embeded File)을 생성한다. 본 연구에서는 제로트리 부호화 과정중 불확실 구간(Uncertainty Interval)에서 발생하는 오차(Error)를 줄이기 위하여 LBG(Line Bute Gray) 알고리즘을 도입하여 최적의 오차 코드북을 생성한 후 복원시 사용함으로써 결과의 향상을 보였다. 오차교정(Error Correction)은 EZW(Embeded Zerotee Wavelet) 부호화 과정에서 손실되기 쉬운 고주파수 밴드에 적용하여 복원시 영상의 자세한(detail) 성분을 살리는데 효과적이다. JPEG과 같은 DCT 기반 영상압축 결과에 비하여 화질에서 더 좋은 성능을 보일뿐아니라, DCT 특유의 블록화 현상도 제거되었다.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.44 no.5
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• pp.94-102
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• 2007

In de-noising, it is wellknown that wavelet-thresholding algorithm shows near-optimal performances in the minimax sense. However, the wavelet-thresholding algorithm is difficult in realization it on hardware, such as FPGA, because of wavelet function complexity. In this paper, we present a new do-noising technique with the binary tree structured filter bank, which is based on the signal power ratio of each subbands to the total signal power. And we realize it on FPGA. For simple realization, the filter banks are designed by Hadamard transform coefficients. The simulation and hardware experimental results show that the performance of the proposed method is similar with that of soft thresholding de-noising algorithm based on wavelets, nevertheless it is simple.

• The Journal of the Acoustical Society of Korea
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• v.15 no.1
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• pp.46-53
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• 1996

Adaptive LMS algorithm has been used in many application areas due to its low complexity. In this paper input signal is transformed into the subbands with arbitrary bandwidth. In each subbands the dynamic range can be reduced, so that the independent filtering in each subbands has faster convergence rate than the full band system. The DCT transform domain LMS adaptive filtering has the whitening effect of input signal at each bands. This leads the convergence rate to very high speed owing to the decrease of eigen value spread Finally, the filtered signals in each subbands are synthesized for the output signal to have full frequency components. In this procedure wavelet filter bank guarantees the perfect reconstruction of signal without any interspectra interference. In simulation for the case of speech signal added additive white gaussian noise, the suggested algorithm shows better performance than that of conventional NLMS algorithm at high SNR.

• The Transactions of the Korea Information Processing Society
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• v.7 no.10
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• pp.3272-3279
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• 2000

In this paper, we propose two fast VQ coclebook search algorithms efficient to the Wavelet/ VQ coding schemes. It is well known that the probability having large values in wavelet coefficient blocks is very low. In order to apply this property to codebook search, the index tables of the reordered codebook in each wavelet subband ae used. The exil condition in PDE can be satisfied in an earlystage by comparing the large coefficients of the codeword with their corresponding elements of input vector using the index tbles. As a result, search time can be reduced.