• 디지털콘텐츠학회 논문지
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• 제5권2호
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• pp.101-105
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• 2004

The block error probabilities of noncoherent frequency shift keying in a Nakagami fading channel are presented in this papaer. The channel fading speed, show or fast. is consider in evaluating block error probabilities. The effectiveness of diversity combing and error correction coding in improving block error performance is examined. The effect of cochannel interference on block error performance is also studied in this paper.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 심포지엄 논문집 정보 및 제어부문
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• pp.167-169
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• 2005

The occurrence of a single bit error in transmission bitstream leads to serious temporal and spatial errors. Because moving picture coding as MPEG-2 based on block coding algorithm uses variable length coding and motion compensation coding algorithm. In this paper, we propose algorithm to conceal occurred error of I-frames in transmission channel using data of the neighboring blocks in decoder. We divide a damaged macroblock of I-frame into four sub blocks and compose new macroblock using the neighboring blocks for each sub block. We estimate the block with minimum difference value through block matching with previous frame for new macroblocks and replace each estimated block with damaged sub block in the same position. Through simulation results, the proposed algorithm will be applied to a characteristic of moving with effect and shows better performance than conventional error concealment algorithms from visual and PSNR of view.

• 한국방송∙미디어공학회:학술대회논문집
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• 한국방송공학회 1999년도 KOBA 방송기술 워크샵 KOBA Broadcasting Technology Workshop
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• pp.57.2-62
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• 1999

Fractal coding is image compression techniques using one of image characteristics self-transformability. In fractal image coding, the encoding process is to select the domain block similar to a range block. The reconstructed image quality of fractal image coding depends on similitude between a range block and the selected domain block. Domain block similar to a range blocks. In fact, the error of the reconstructed image adds up the generated error in encoding process and the generated error in decoding process. But current domain block estimating function considered only the encoding error. We propose a domain block estimating function to consider not only the encoding error but also the decoding error. By computer simulation, it was verified to obtain the high quality reconstructed image.

• Journal of information and communication convergence engineering
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• 제4권4호
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• pp.131-135
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• 2006

In this paper, we discusses that the theoretical analysis is made for the performance of FS MC-CDMA by the aid of the Nakagami fading channels and the block error probabilities of the FS MC-CDMA in Nakagami fading channel are presented. The channel fading speed, slow or fast, is considered in evaluating block error probabilities. The effectiveness of diversity combining in improving block error performance is examined.

• 한국통신학회논문지
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• 제22권5호
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• pp.915-927
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• 1997

In this paper, we propose an error concealment technique using directional interpolation in block-based image compression. In the proposed method the edge direction is determined by finding the maximum correlation coefficients of boundary pixels of blocks neighboring the errored block in spatial domain. Then the errored block is interpolated linearly or bilinearly along the determined edge direction. The proposed method can conceal the block error, the macro block error, and the slice error adaptively. Also, the parameters for the directional interpolation are represented by closed forms. When applied to compressed images, the proposed method shows superior subjective and objective quality to conventional error concealment methods.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 학술대회 논문집 정보 및 제어부문
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• pp.12-14
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• 2005

In this paper, we proposed an temporal error concealment (EC) using the proposed boundary matching method and the adaptive block matching method. The proposed boundary matching method improves the spatial correlation of the macroblocks (MBs) by reusing the pixels of the concealed MB to estimate a motion vector of a error MB. The adaptive block matching method inspects the horizontal edge and the vertical edge feature of a error MB surroundings, and it conceals the error MBs in reference to more stronger edge feature. This improves video quality by raising edge connection feature of the error MBs and the neighborhood MBs. In particular, we restore a lost MB as the unit of 8${\times}$16 block or 16${\times}$8 block by using edge feature from the surrounding macroblocks. Experimental results show that the proposed algorithm gives better results than the conventional algorithms from a subjective and an objective viewpoint.

• 스마트미디어저널
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• 제6권2호
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• pp.9-14
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• 2017

무선 환경에서의 패킷 손실은 비디오 통신과정에서 심각한 비디오 품질 저하를 초래한다. 이 논문에서는 블록의 신뢰도와 블록 경계면 매칭을 기반으로 한 비디오 에러 은닉 기술에 대해서 제안한다. 손실된 블록의 모션 정보를 참조 프레임의 동일한 위치에 존재하는 블록의 모션 정보를 복사하여 사용함으로써 임시로 손실된 블록의 잡음을 은닉하고, 블록의 신뢰도를 기준으로 블록의 신뢰도가 낮은 경우에는 추가적으로 블록의 경계면 매칭을 이용하여 모션 벡터를 재탐색하여 잡음 은닉에 대한 정확도를 높이도록 하였다. 실험을 통해서 제안된 기법이 다양한 패킷 손실 환경에서 우수한 에러 은닉 성능을 보임을 확인하였다.

• 한국통신학회논문지
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• 제29권8C호
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• pp.1125-1132
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• 2004

본 논문에서는 블록기반으로 부호화된 비디오 영상에서 전송 오류로 인하여 발생하는 화질저하를 개선하기 위하여 인과적 블록경계 정합법을 사용하여 효율적으로 복호가능 오류를 검출하는 알고리즘을 제안하였다. 제안된 방법에서는 먼저 현재 블록의 경계들과 인과적 주위블록외 경계들간 부정합 전력을 계산한다. 다음, 이렇게 구한 부정합 전력들 중 하나라도 인과적 주위 블록들의 통계적 특성을 사용하여 적응적으로 구한 역치보다 크면 오류가 있는 것으로 판단한다. 실제로 H.263으로 부호화된 비디오를 가지고 $10^{-3}$-$10^{-4}$ BERs에서 16비트 연속적인 비트 에러를 가지는 환경에서 제안한 방법을 적용하였다. 기존의 블록경계정합 오류검출법의 하나인 Zeng의 방법과 비교하면, 에러 검출율의 향상은 최대 20%, 그리고 검출된 오류를 은닉 처리한 결과영상의 PSNR 향상은 최대 3.5㏈임을 보여준다.

• 전자공학회논문지B
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• 제28B권5호
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• pp.318-326
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• 1991

A Quantizer reconstruction level control method for block artifact reduction in DCT image coding is described. In our scheme, quantizer reconstruction level control is obtained by adding quantization level step size to the optimum quantization level in the direction of reducing the block artifact by minimizing the mean square error(MSE) and error difference(EDF) distribution in boundary without the other additional bits. In simulation results, although the performance in terms of signal to noise ratio is degraded by a little amount, mean square of error difference at block boundary and mean square error having relation block artifact is greatly reduced. Subjective image qualities are improved compared with other block artifact reduction method such as postprocessing by filtering and trasform coding by block overlapping. But the addition calculations of 1-dimensional DCT become to be more necessary to coding process for determining the reconstruction level.

• Journal of Communications and Networks
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• 제10권3호
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• pp.253-257
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• 2008

In this paper, the performance of generic orthogonal space-time block codes (OSTBCs) introduced by Alamouti [2], Tarokh [3], and Su and Xia [11] is analyzed. We first define one-dimensional component symbol error function (ODSEF) from the exact expression of the pairwise error probability of an OSTBC. Utilizing the ODSEF and the bit error probability (BEP) expression for quadrature amplitude modulation (QAM) introduced by Cho and Yoon [9], the exact closed-form expressions for the BEP of linear OSTBCs with QAM in quasi-static Rayleigh fading channel are derived. We also derive the exact closed-form of the BEP for some OSTBCs which have at least one message symbol transmitted with unequal power via all transmit antennas.