• 전자공학회논문지A
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• 제32A권10호
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• pp.64-72
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• 1995

In this paper, atmospheric turbulence and absorption under clear weather condition, which affect the optical satellite up-link communication between geo-satellites and earth station, were studied. In case of the up-link communication, the received optical power is weakened by pointing loss caused by beam tilt which is the main effect of turbulent atmosphere. This pointing loss directly has relation to the diameter of optical transmitting antenna. From the inverse proportion of the pointing and spaced loss, it is the regions where the diameter of transmitting antenna increases abruptly and the efficient design of transmitting antenna is impossible. In case of using channel coding, it was shown that the peak value of diameter moved to the lower regions of elevation angle with increasing the coding gain and its width was also decreased. In case of considering both coding gain and transmission rate on the design of transmitting antenna, it was known that more coding gain was necessary as transmission rate was increased.

• 한국전자파학회논문지
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• 제13권9호
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• pp.889-897
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• 2002

본 논문에서는 OFDM(Orthogonal Frequency Division Multiplexing) 통신 시스템에서 발생하는 중요한 문제점인 PAPR(Peak to Average Power Ratio)을 저감하기 위하여 개선된 블록 코딩 방식을 제안하고 코딩 이득을 분석한다. 부반송파수가 N인 경우, 기존 블록 코딩 방식에서는 블록 인코더 1 개를 이용하지만, 제안된 블록 코딩 방식은 블록 인코더 2개를 이용한다. 이 방식은 기존 블록 코딩과 비교하여 동일한 PAPR 저감 능력을 가지면서도 코드율을 2배로 증가시켜서 스펙트럼 효율을 2배로 개선시킨다. 또한 코드 블록당 1 개의 오류가 정정된다는 가정 하에서 BER 성능 평가를 수행하였다.

• Journal of Communications and Networks
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• 제1권3호
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• pp.182-188
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• 1999

The optimal joint maximum-likelihood sequence estima-for using an array of antennas is derived for synchronous direct sequence-code division multiple access (DS-CDMA) system. Each user employs a rate 1/n convolutional code for channel coding for the additive white Gaussian noise (AWGN) channel. The array re-ceiver structure is composed of beamformers in the users' direc-tions followed by a bank of matched filters. The decoder is imple-mented using a Viterbi algorithm whose states depend on the num-ber of users and the constraint length of the convolutional code. The asymptotic array multiuser coding gain(AAMCG)is defined to encompass the asymptotic multiuser coding gain and the spatial information on users' locations in the system. We derive the upper and lower bounds of the AAMCG. As an example, the upper and lower bounds of AAMCG are obtained for the two user case where each user employes the maximum free distance convolutional code with rate 1/2. The enar-far resistance property is also investigated considering the number of antenna elements and user separations in the space.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2007년도 7th International Meeting on Information Display 제7권2호
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• pp.1508-1511
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• 2007

This paper introduces a new texture prediction for MVC( Multi-view Video Coding) which is currently being developed as an extension of the ITU-T Recommendation H.264 | ISO/IEC International Standard ISO/IEC 14496-10 AVC (Advanced Video Coding) [1]. The MVC's prcimary target is 3D video compression for 3D display system, thus, key technology compared to 2D video compression is reducing inter-view correlation. It is noticed, however, that the current JMVM [2] does not effectively eliminate inter-view correlation so that there is still a room to improve coding efficiency. The proposed method utilizes similarity of interview residual signal and can provide an additional coding gain. It is claimed that up to 0.2dB PSNR gain with 1.4% bit-rate saving is obtained for three multi-view test sequences.

• 한국공작기계학회논문집
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• 제13권3호
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• pp.126-132
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• 2004

This paper proposed trajectory tracking control based on genetic algorithm. Trajectory tracking control scheme are real coding genetic algorithm(RCGA) and back-propagation algorithm(BPA). Control scheme ability experience proposed simulation. Stable tracking control problem of mobile robots have been studied in recent years. These studies have guaranteed stability of controller, but the performance of transient state has not been guaranteed. In some situations, constant gain controller shows overshoots and oscillations. So we introduce better control scheme using real coding genetic algorithm and neural network. Using RCGA, we can find proper gains in several situations and these gains are generalized by neural network. The generalization power of neural network will give proper gain in untrained situation. Performance of proposed controller will verity numerical simulations and the results show better performance than constant gain controller.

• 한국멀티미디어학회논문지
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• 제6권7호
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• pp.1159-1168
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• 2003

본 논문에서는 압축 효율을 최적화 하는 웨이브렛 필터의 설계 알고리즘을 제안하였다. 제안한 알고리즘은 고정 양자화기를 이용하는 영상 부호화 응용에서 압축 방법에 상관없이 웨이브렛 변환 영역에서 각 대역의 에너지를 가장 불균등하게 압축하는 필터를 설계함으로써 전체적인 부호화 효율을 높일 수 있도록 하였다. 직교와 쌍직교 필터에서의 목적함수는 웨이브렛 변환 계층에 맞도록 확장시켜 각 계층별로 최적 필터 계수를 얻었으며 최적화 과정의 제한조건을 완화하여 압축이득을 최대화시킬 수 있도록 하였다. 제안한 방법으로 설계한 필터는 실험 결과 기존의 필터와 비교하여 에너지 압축이득이 향상되었음을 알 수 있었다.

• 한국방송∙미디어공학회:학술대회논문집
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• 한국방송공학회 2009년도 IWAIT
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• pp.326-329
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• 2009

This paper proposes a new video compression algorithm using an adaptive transform that is adjusted depending on the frequency contents of the input signals. The adaptive transform is based on the warped discrete cosine transform (WDCT) which is shown to provide better performance than the DCT at high bit rates, when applied to JPEG compression scheme [1, 2, 3]. The WDCT is applied to the video compression in this paper, as a new feature in the H.264/AVC. The proposed method shows the coding gain over the H.264/AVC at high bit rates. The coding gain is shown over the 35dB PSNR quality, and the gain increases as the bit rate increases. (about 1.0dB at 45dB PSNR quality at maximum)

• 대한전자공학회논문지SP
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• 제49권2호
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• pp.83-93
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• 2012

본 논문에서는 다시점의 컬러 영상 및 깊이 정보 맵을 효율적으로 압축하는 방법을 제안한다. 제안하는 다시점 컬러 영상과 깊이 정보 맵 압축 방법을 통하여, 컬러 영상과 깊이영상이 각각 동일시점 내에서 화면 간 참조를 수행함은 물론, 확장 시점의 컬러 영상과 깊이 정보 맵이 이웃한 시점의 컬러 영상과 깊이 정보 맵을 각각 참조하는 시점 간 참조를 추가적으로 수행함으로써 부호화 효율을 높일 수 있다. 제안한 방법을 통하여 실험을 수행한 결과 2시점의 경우 컬러 영상은 각 시점의 영상을 시점간 부호화 하지 않은 영상에 비하여 약 55%의 부호화 이득이 있었으며 깊이 정보 맵은 약 12%의 부호화 이득이 있었다. 3시점의 경우에는 컬러 영상에 대하여 바깥 시점은 화면 간 예측 부호화를 하지 않은 영상에 비해 54%, 중간 시점은 56%의 비트를 절약할 수 있었다. 또한, 3시점의 깊이 정보 맵에 대하여 예측 부호화를 하지 않은 영상에 비해 약 11%의 바깥 시점 부호화 성능과 13%의 중간 시점 부호화 성능을 얻을 수 있었다.

• Journal of Communications and Networks
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• 제5권3호
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• pp.187-196
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• 2003

We consider the use of error control coding in direct sequence-code-division multiple access (OS-COMA) systems that employ multiuser detection (MUO) and space diversity. The relative performance gain between Reed-Solomon (RS) code and convolutional code (CC) is well known in [1] for the single user, additive white Gaussian noise (AWGN) channel. In this case, RS codes outperform CC's at high signal-to-noise ratios. We find that this is not the case for the multiuser interference channel mentioned above. For useful error rates, we find that soft-decision CC's to be uniformly better than RS codes when used with DS-COMA modulation in multiuser space-time channels. In our development, we use the Gaussian approximation on the interference to determine performance error bounds for systems with low number of users. Then, we check their accuracy in error rate estimation via system's simulation. These performance bounds will in turn allow us to consider a large number of users where we can estimate the gain in user-capacity due to channel coding. Lastly, the use of turbo codes is considered where it is shown that they offer a coding gain of 2.5 dB relative to soft-decision CC.

• 대한전자공학회논문지
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• 제26권10호
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• pp.1561-1570
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• 1989

In this paper, we propose an image coding scheme which combines the Laplacian pyramid structure and a hierarchical finite state classified vector quantizer in the DCT domain, namely FSDCT-CTQ. First, an optimal bit allocation problem for fixed rates DCT-CVQ on the Laplacian pyramid structure is described. In an asymptotic case, with an optimal bit allocation, a coding gain over scalar quantization of each Laplacian plane is derived. Second, it is experimentallhy shown that the Laplacian pyramid structure provides a considerable codng gain in the sense of total MMSE (minimum mean squared error). Finally, we propose an FS-DCT-CVQ which exploits the hierarchicla correlation between the Laplacian planes. Simulation results on real images show that the proposed coding scheme can reconstruct an image with 30.33 dB at 0.192 bpp, 32.45 dB at 0.385 bpp, respectively.