• Journal of the Institute of Electronics Engineers of Korea CI
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• v.48 no.1
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• pp.60-64
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• 2011

In this paper, we propose a new post-processing technique that removes blocking and ringing artifacts in Block discrete cosine transformation (BDCT)-coded images using bilateral filtering. The selection of filter parameters is a key issue in the application of a bilateral filter because it significantly affects the result. An efficient method of selecting the bilateral filter parameters is presented. The experimental results show that the proposed approach alleviates the artifacts efficiently in terms of PSNR, MSDS, and SSIM.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.10 no.5
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• pp.147-151
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• 2010

In this paper, we propose network-coding based two-way relay communication using adaptive modulation scheme for satisfying relay QoS(Quality of Service) according to channel environment between user and relay. Two-way relay communication is bidirectional cooperative communication that users exchange own signal with help of relay. Network-coding based two-way relay communication can achieve high throughput compared to conventional scheme through reducing time slots. we propose adaptive M-QAM modulation scheme in network-coding based two-way relay communication for satisfying QoS of relay. Simulation result shows that the proposed scheme satisfies goal QoS of system.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.9 no.5
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• pp.7-13
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• 2009

In This Paper, we propose relay schemes for network-coding based two-way relay communication in multi relay channel. Two-way relay channel communication is a bi-directional communication that two users exchange their data with the help of a relay. Network-coding based Two-way relay communication can achieve more throughput compared to conventional two-way relay communication. In this paper, we propose relay selection schemes to provide maximum performance considering instantaneous signal-to-noise in multi-relay channel. Simulation results show that the proposed relay selection schemes can provide diversity order according to the number of relays.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.10A
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• pp.972-979
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• 2008

Two-way relay channel is a bidirectional cooperative communication channel that two terminals communicate each other with the help of a relay. In the previous cooperative communication schemes, a relay uses two divided resources for bidirectional transmission. When a network coding is used at a relay, the relay can transmit bidirectional data to two terminals simultaneously using one resource only. Thus the throughput of this scheme is greater than that of the previous scheme. In this paper, we showa two-way cooperative ARQ protocol using network coding and the throughput of this protocol is analyzed using a state diagram.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2012.11a
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• pp.67-68
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• 2012

전이중(full-duplex) 양방향 중계 네트워크는 전이중 방식을 사용하는 중계기에서 물리 계층 네트워크 부호화(physical layer network coding) 혹은 중첩 부호화(superposition coding)을 사용하여 기존 반이중(half duplex) 중계기를 사용하는 양방향 중계 네트워크에 비해 높은 주파수 효율을 제공한다. 본 논문에서는 전이중 양방향 중계 네트워크를 고려하여 전이중 방식에서 필연적으로 발생하는 루프간섭 신호의 영향을 살펴보았다. 여기에서 사용자 및 중계기는 루프간섭 신호를 제거하기 위해 루프간섭 신호를 추정한다. 하지만 루프간섭 신호를 추정할 때 추정 오류가 발생하여 수신 신호에서 루프간섭 신호를 완벽하게 제거하기는 어렵다. 모의실험에서는 이로 인해 발생할 수 있는 성능 변화를 불능 확률을 통해 분석하였다.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2003.11a
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• pp.133-138
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• 2003

가변길이 부호는 정보원(source)의 통계적인 특성을 이용하여 부호화 효율을 높이지만. 잡음이 심한 전송환경에선 비트에 대한 오류가 발생하면 심각하게 손상되는 단점을 가진다. 이러한 가변길이 부호의 문제를 해결하기 위해 양방향 가변길이 부호가 제안되었다. 양방향 가변길이 부호는 순방향과 역방향으로 복호가 가능하여 전송 오류로 인해 손상된 비디오 비트열에서 데이터를 복구할 수 있다. 부호의 자유거리(free distance)는 부호자체가 전송 오류에 얼마나 강인한지를 보여주는 척도로 사용된다. 양방향 가변길이 부호의 자유거리(free distance)의 최소 값은 1이므로 비디오 비트열 손상 자체를 방지할 수는 없다 본 논문에서는 자유거리(free distancs)의 최소 값을 증가시켜 전송오류에 더욱 강인한 새로운 양방향 가변길이 부호의 선계 기법을 제안한다. 제안된 알고리즘은 주어진 Huffman 부호와 평균부호길이 함수의 특성을 이용하여 자유거리의 조건을 만족하면서 동시에 부호화 효율을 높여 기존의 알고리즘보다 향상된 성능을 보여준다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.2B
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• pp.97-109
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• 2012

In this paper, we propose a modulation scheme for a network-coded bi-directional relaying (NBR) system over an asymmetric channel, which means that the qualities of the relay channel (the link between the BS and RS) and access channel (the link between the RS and MS) are not identical. The proposed scheme employs a dual constellation in such a way that the RS broadcasts the network-coded symbols modulated by two different constellations to the MS and BS over two consecutive transmission intervals. We derive an upper bound on the average bit error rate (BER) of the proposed scheme, and compare it with the hybrid constellation-based modulation scheme proposed for the asymmetric bi-directional link. Furthermore, we investigate the channel utilization of the existing bi-directional relaying schemes as well as the NBR system with the proposed dual constellation diversity-based modulation (DCD). From our simulation results, we show that the DCD gives better average BER performance about 3.5~4dB when $E_b/N_0$ is equal to $10^{-2}$, while maintaining the same spectral efficiency as the existing NBR schemes over the asymmetric bi-directional relaying channel.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.41 no.1
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• pp.57-68
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• 2004

Although variable-length codes (VLCs) increase coding efficiency using the statistical characteristics of the source data, they have catastrophic effects from bit errors in noisy transmission environments. In order to overcome this problem with VLCs, reversible variable-length codes (RVLCS) have recently been proposed owing to their data recovering capability. RVLCS can be divided into two categories: symmetrical and asymmetrical RVLCs. Although the symmetrical RVLC has generally more overheads than the asymmetrical RVLC, it has some advantages of simpler design and more efficient memory usage. However, existing symmetrical RVLCs still have high complexity in their code design and some room for improvement in coding efficiency. In this paper, we propose a new algorithm for constructing a symmetrical RVLC from the optimal Huffman code table. The proposed algorithm has a simpler design process and also demonstrates improved performance in terms of the average codeword length relative to the existing symmetrical RVLC algorithms.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.42 no.1
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• pp.1-7
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• 2005

We propose an effective Landsat TM image compression method using the classified bidirectional prediction (CBP), the classified KLT and the SPIHT. The SPIHT is used to exploit the spatial redundancy of feature bands selected in the visible range and the infrared range separately. Regions of the prediction bands are classified into three classes in the wavelet domain, and then the CBP is performed to exploit the spectral redundancy. Residual bands that consist of difference values between the original band and the predicted band are decorrelated by the spectral KLT Finally, the three dimensional (3-D) SPIHT is used to encode the decorrelated coefficients. Experiment results show that the proposed method reconstructs higher quality Landsat TM image than conventional methods at the same bit rate.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 1995.06a
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• pp.105-108
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• 1995

본 논문에서는 초기 비트율 부호화(very low bit-rate coding)를 위한 새로운 움직임 예측 부호화를 제안한다. 움직임 추정 및 움직임 보상은 영역 기반으로 행해지며, 움직임 보상 후 예측 오차는 DCT(Discrete Cosine Transform)를 통해 변환되어 부호화 된다. 제안된 내용으로는 이전 영상을 이용하여 역방향(backward) 움직임 추정 후 얻어지는 움직임 벡터를 이용하여 움직임 보상된 영상을 구성하고, 여기에 보상되지 않은 영역은 순방향(forward) 움직임 추정을 선택적으로 행함으로써 영상을 재구성한다. 제안된 알고리듬은 모의 실험 결과 양질의 화질을 얻었다.