• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.7A
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• pp.960-966
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• 2000

It is essential to develop the robust video transmission system over wireless channel, since the effect of the noise and the interference to compressed video may be fatal. In this paper, we have designed turbo code, which is adequate for the transmission of video and analyzed the performance of that. Especially, we have focused the rate compatible punctured turbo(RCPT) code, which has rate compatible(RC) property for unequal error protection(UEP). It has been shown through computer simulation that the turbo code with helical interleaver yields better performance than those with other interleavers when the size of the interleaver is not large.

• Journal of Information Management
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• v.42 no.1
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• pp.47-62
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• 2011

While an ideal author graph should have its nodes to represent authors, automatically-generated author graphs mostly use author names as their nodes due to the difficulty of resolving author names into individuals. However, employing author names as nodes of author graphs merges namesakes, otherwise separate nodes in the author graph, into the same node, which may distort the characteristics of the author graph. This study proposes an algorithm which resolves author ambiguities based on co-authorship and then yields an author graph consisting of not author name nodes but author nodes. Scientific collaboration relationship this algorithm depends on tends to produce the clustering results which minimize the over-clustering error at the expense of the under-clustering error. In experiments, the algorithm is applied to the real citation records where Korean namesakes occur, and the results are discussed.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.24 no.9B
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• pp.1742-1754
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• 1999

In this paper, we propose a rate control scheme, using histogram based rate-distortion (R-D) estimation, which produces a consistent picture quality between consecutive frames. The histogram based R-D estimation used in our rate control scheme offers a closed-form mathematical model that enable us to predict the bits and the distortion generated from an encoded frame at a given quantization parameter (QP) and vice versa. The most attractive feature of the R-D estimation is low complexity of computing the R-D data because its major operation is just to obtain a histogram or weighted histogram of DCT coefficients from an input picture. Furthermore, it is accurate enough to be applied to the practical video coding. Therefore, the proposed rate control scheme using this R-D estimation model is appropriate for the applications requiring low delay and low complexity, and controls the output bit-rate ad quality accurately. Our rate control scheme ensures that the video buffer do not underflow and overflow by satisfying the buffer constraint and, additionally, prevents quality difference between consecutive frames from exceeding certain level by adopting the distortion constraint. In addition, a consistent considering the maximum tolerance BER of the voice service. Also in Rician fading channel of K=6 and K=10, considering CLP=$10^{-3}$ as a criterion, it is observed that the performance improment of about 3.5 dB and 1.5 dB is obtained, respectively, in terms of $E_b$/$N_o$ by employing the concatenated FEC code with pilot symbols.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.2
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• pp.705-713
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• 2021

Because the cage assembly serves as the launch platform, an accurate aim is essential to ensure shooting accuracy for the target. On the other hand, the abnormal rotation of the cage due to the directional errors of the K-MLRS has continuously caused quality problems. The quality problem of weapon systems may have a negative impact on the military's power loss. In this study, improvement plans were derived by examining the defects and analyzing the directional errors of the K-MLRS launcher. In addition, all possible causes of directional errors were derived from the flow diagram for cage directionality. Based on the results, the defense design through the software program was intended to prevent the loss of direction. Through this study, the signal error of the resolver was improved by preventing unspecific signals in the data. Furthermore, the directional judgment method was improved to minimize the impact of data distortion. Lastly, directional storage and verification methods were improved so that data for the cage rotation direction would not be affected by errors. For the design improvement method, the reliability was verified through the system applicability. This study is expected to be a reference for failure analysis and design for similar weapon systems in the future.

• Journal of KIISE:Software and Applications
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• v.37 no.6
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• pp.417-429
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• 2010

Reversible watermarking inserts watermark into digital media in such a way that visual transparency is preserved and then enables to restore the original media from the marked one without any loss of media quality. This watermarking can be applied to quality-sensitive imaging such as medical imaging, military imaging, remote-sensing imaging, and precious artwork, where the original media should be preserved during image processing and analysis. In this paper, a reversible image watermarking technique that embeds message bits by modifying the differential histogram of adjacent pixels is presented. In order to satisfy both high embedding capacity and visual quality, the proposed technique exploits the fact that adjacent pixels in the image have highly spatial correlation. Also, we prevent overflow/underflow problem and salt-and-pepper artifacts by employing a predicted error compensation scheme. Through experiments using various test images, we prove that the presented technique provides perfect reversibility and high embedding capacity, while maintaining the induced-distortion low.

• The Journal of the Korea institute of electronic communication sciences
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• v.14 no.1
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• pp.69-80
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• 2019

This paper proposes a multimodal sensor platform which supports plug and play (PnP) technology. PnP technology automatically recognizes a connected sensor module and an application program easily controls a sensor. To verify a multimodal platform for PnP technology, we build up a firmware and have the experiment on a sensor system. When a sensor module is connected to the platform, a firmware recognizes the sensor module and reads sensor data. As a result, it provides PnP technology to simply plug sensors without any software configuration. Measured sensor raw data suffer from various distortions such as gain, offset, and non-linearity errors. Therefore, we introduce a polynomial calculation to compensate for sensor distortions. To find the optimal coefficients for sensor calibration, we apply a genetic algorithm which reduces the calibration time. It achieves reasonable performance using only a few data points with reducing 97% error in the worst case. The platform supports various protocols for multimodal sensors, i.e., UART, I2C, I2S, SPI, and GPIO.

• Proceedings of the Acoustical Society of Korea Conference
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• spring
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• pp.49-52
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• 2004

본 논문에서는 켑스트럼 기반의 후두질환 음성의 자동감별시, 훈련 및 테스트 마이크 불일치로 인한 채널 왜곡을 보상하기 위한 방법에 대해 연구를 하였다. 특징벡터 영역에서의 채널보상 방법으로 기존의 Cepstral Mean Subtraction (CMS) 방법과 Pole Filtering CMS (FPCMS) 방법을 이용하였다 실험결과 FPCMS를 적용한 경우 기존의 CMS에 비해 우수한 성능을 보이고, $40\%$의 인식 오류 감소를 얻었다.

• Proceedings of the KIEE Conference
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• 2008.10b
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• pp.143-144
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• 2008

본 논문은 오디오 압축시 하모닉의 특성을 적용함으로써 신호의 압축률을 향상시킬 수 있도록 하는 내용을 기술하고 있다. 하모닉 코딩은 오디오 신호가 가지는 특징인 복합음(Complex tone)의 특성을 이용하는 것으로, 주파수 공간에서 정수배의 주파수가 존재하며, 정면파의 특성상 시간적으로 인접 신호들간의 유사성이 매우 높은 특징을 이용하여 압축효율을 향상시키는 방법이다. 하지만 실질적인 오디오 신호의 경우, 악기들의 harmonic stretch, 전달과정에서 발생하는 신호의 왜곡, 외부 잡음등의 특성으로 인하여 수집된 오디오 신호를 분석하는 과정에서 부정확한 하모닉의 판단이 이루어질 가능성이 높으며, 이는 압축과정에서 심각한 음질의 열화를 가져오게 된다. 따라서 본 논문에서는 프레림간의 변화 추이의 판단을 통하여 하모닉의 변화를 예측하고, 예측 오류에 대한 보상값을 전달함으로써 오디오 신호의 안정적인 압축/복원이 가능하도록 하는 신호처리 방법에 대한 내용을 기술하고있다.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2011.07a
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• pp.563-564
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• 2011

본 논문에서 우리는 unequal loss protection(ULP) 알고리즘을 기반으로 패킷이 손실될 수 있는 망 환경에서 인지적으로 재구성된 영상의 왜곡을 최소화하는 방법을 제안한다. 알고리즘에는 2가지의 주요 요인이 있다. 첫째, 인간 시각 체계의 균일하지 않은 분포의 함수로 압축된 영상에 가중치를 준다. 둘째, 패킷은 오류 전파가 일어나지 않도록 하면서 각각의 group of picture(GOP)내에서 시간적인 중요성이 할당된다. 프레임의 인지적인 중요성과 GOP의 계층적인 중요성을 동시에 고려하여, 제안하는 ULP알고리즘은 인간 시각적으로 가장 중요한 지역의 크기를 식별하여 효율적인 forword error correction(FEC) 알고리즘을 수행한다.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 2004.10a
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• pp.481-484
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• 2004

본 논문에서는 적응형 OFDM 시스템의 채널 추정 알고리즘과 무선 채널환경에서 시스템에 미치는 영향을 분석하고 추정된 결과를 이용하여 적응형 등화기를 적용한 적응형 OFDM 시스템의 성능을 BER과 성좌도를 통하여 분석한다. 분석결과, 기존의 고정된 변조 방식을 사용하는 시스템인 경우 고속의 데이터 전송을 위해 높은 지수의 변조모드(64QAM)를 사용함으로써 채널 환경에 민감하게 심볼오류 발생률이 증가함을 알 수 있었다. 하지만 채널상태에 따라 가변을 취하는 적응형 OFDM 시스템의 경우 64QAM방식에 비해 (BER=10-2)를 기준으로 약 8dB 성능의 이득이 있음을 알 수 있고 적응형 등화기를 적용함에 따라 왜곡을 받은 신호 파형의 보상이 가능함을 알 수 있다. 무수한 장애의 요인을 갖은 무선 채널환경에서 효율적인 데이터 전송을 위해 적응변조시스템이 요구되어짐을 알 수 있었다.