• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2010.07a
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• pp.126-129
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• 2010

본 논문에서는 패킷 오류가 발생하는 IP 망을 통해 비디오 전송 서비스를 제공하기 위한 조건적 ARQ 기반의 오류 제어기법을 제안한다. IP 망에서 패킷 손실이 발생하면 수신 단말은 서버에게 손실된 패킷의 재전송을 요청할 수 있다. 그러나 망 상황과 접속 단말 개수를 고려하지 않고 무조건적인 재전송을 요청 할 경우 손실된 패킷이 복호화에 필요한 시점까지 도착 할 것인지가 보장되지 않을 뿐더러, 오히려 불필요한 재전송 요청에 의해 망에서의 트래픽 량을 가중시킬 수 있다. 따라서 망 상황을 고려하여 손실된 패킷이 재전송에 의해 적절한 시간 내에 도착이 가능한지를 판단하여 조건적으로 ARQ를 요청하는 기술이 요구된다. 본 논문에서는 기존의 RFC 문서에서 권고하는 재전송 관련 메카니즘들을 효과적으로 활용하여 표준기술 기반의 조건적 ARQ 오류제어 기법을 제안한다. 제안된 기법에서는 단말에서 추정된 망 상황을 기반으로 조건적으로 재전송 요청 여부를 결정하고, 더 나아가서 유효한 재전송 요청 시점을 결정하여 보다 효율적인 ARQ 가 적용될 수 있도록 한다. 제안된 조건적 ARQ 기반의 오류 제어 기법의 성능을 검증하기 위하여 패킷 손실 네트워크 환경을 NIST-Net을 활용하여 구축하며 실험 결과를 통해 제안된 기법의 우수한 오류 강인 성능을 확인한다.

• The Transactions of the Korea Information Processing Society
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• v.3 no.2
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• pp.275-282
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• 1996

For interchange of multimedia informations and presentation as intented by objects composer, there are need to interchange format of informations and control synchronization between medias. And It is therefore need to provide a method and apparatus for synchroniztion control of multimedia objects which can control the conditional, temporal. and spatial synchronization in a MHEG engine developed to execute the functions defined as the international standards. In this paper. We propose to improved method and apparatus for synchronization control of multimedia objects which can execute the synchronized presentation by combining media data needed for presentation of multimedia information, and which enable the interactive processing between the user and the MHEG engine by allowing the user input to be processed during presentation.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2013.05a
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• pp.629-631
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• 2013

In this paper, a novel transmission system based on ATSC-M/H is proposed that enables free broadcast content services and pay subscription based content services. The proposed system is compatible with the existing systems and it does not use complex access restriction mechanisms such as CAS. In North America, many DLNA systems use set-top boxes with DVR as a digital media server. A method to enable the provision for ATSC-M/H free and pay subscription services on DLNA systems is presented. In addition, a data service processing method in DLNA systems is also proposed.

• International Journal of Fuzzy Logic and Intelligent Systems
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• v.13 no.3
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• pp.186-199
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• 2013

We pose pattern classification as a density estimation problem where we consider mixtures of generative models under partially labeled data setups. Unlike traditional approaches that estimate density everywhere in data space, we focus on the density along the decision boundary that can yield more discriminative models with superior classification performance. We extend our earlier work on the recursive estimation method for discriminative mixture models to semi-supervised learning setups where some of the data points lack class labels. Our model exploits the mixture structure in the functional gradient framework: it searches for the base mixture component model in a greedy fashion, maximizing the conditional class likelihoods for the labeled data and at the same time minimizing the uncertainty of class label prediction for unlabeled data points. The objective can be effectively imposed as individual mixture component learning on weighted data, hence our mixture learning typically becomes highly efficient for popular base generative models like Gaussians or hidden Markov models. Moreover, apart from the expectation-maximization algorithm, the proposed recursive estimation has several advantages including the lack of need for a pre-determined mixture order and robustness to the choice of initial parameters. We demonstrate the benefits of the proposed approach on a comprehensive set of evaluations consisting of diverse time-series classification problems in semi-supervised scenarios.

• Journal of Broadcast Engineering
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• v.1 no.1
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• pp.1-6
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• 1996

Digital DBS service using Korea Sat starts at Korea Telecom's Yong-in transmission site. Total 6 transmitting stations are needed. At each transmitting station, 4 TV programs are compressed and multiplexed using MPEG-2, modulated into IF, RF signals, then finally transmitted through antenna. At DBS transponder, received signal is down converted, amplified and re-transmitted to earth. At receiver, signal is received by 45cm dish antenna, then wanted program is selected, demultiplexed and decoded. Transmission performance of BER lOE-ll is implemented by using FEe coding and QPSK modulation. For pay TV management, conditional access system, smart card and modem are used.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2012.11a
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• pp.44-45
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• 2012

좌우 해상도가 차이나는 융합형 3DTV의 화질을 개선하기 위한 기법으로써 두 영상간의 양안시차 정보를 활용하는 조건부 대체 알고리즘이 제안된 바 있다. 본 논문에서는 양안시차 벡터의 정밀도가 조건부 대체 알고리즘에 미치는 영향을 살펴보기 위해 양안시차 벡터 추정에 사용되는 좌영상의 해상도에 따른 알고리즘의 성능을 비교한 실험결과를 제시하였다. 높은 해상도의 좌영상을 사용하여 양안시차 벡터의 정밀도가 높아질수록 확장된 우영상의 객관적 화질 및 합성된 3D영상의 자연스러운 입체감이 향상됨을 확인하였다.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 1999.06a
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• pp.83-88
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• 1999

In this paper, a novel gray-scale lossless image coder combining context-based minimum mean squared error (MMSE) prediction and entropy coding is proposed. To obtain context of prediction, this paper first defines directional difference according to sharpness of edge and gradients of localities of image data. Classification of 4 directional differences forms“geometry context”model which characterizes two-dimensional general image behaviors such as directional edge region, smooth region or texture. Based on this context model, adaptive DPCM prediction coefficients are calculated in MMSE sense and the prediction is performed. The MMSE method on context-by-context basis is more in accord with minimum entropy condition, which is one of the major objectives of the predictive coding. In entropy coding stage, context modeling method also gives useful performance. To reduce the statistical redundancy of the residual image, many contexts are preset to take full advantage of conditional probability in entropy coding and merged into small number of context in efficient way for complexity reduction. The proposed lossless coding scheme slightly outperforms the CALIC, which is the state-of-the-art, in compression ratio.

• Journal of Broadcast Engineering
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• v.13 no.1
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• pp.152-161
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• 2008

We investigate that when we restrict the encoding modes on the enhancement layer based on that of the base layer exploiting the high correlation between the best modes at base and enhancement layers, we should determine the set of surviving search modes to yield the minimum excessive RD-cost caused by the restriction. Based on these sets, we implement a fast mode decision algorithm for H.264 Scalable Extension (SE). Simulation results show that the proposed algorithm is superior in the sense of the RD-performance to the conventional mode restriction method which is based on the conditional probabilities of the best modes.

• Journal of Broadcast Engineering
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• v.25 no.1
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• pp.1-12
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• 2020

In the medical field, numerical imbalance of data due to differences in disease prevalence is a common problem. It reduces the performance of a artificial intelligence network, leading to difficulties in learning a network with good performance. Recently, generative adversarial network (GAN) technology has been introduced as a way to address this problem, and its ability has been demonstrated by successful applications in various fields. However, it is still difficult to achieve good results in solving problems with performance degraded by numerical imbalances because the image resolution of the previous studies is not yet good enough and the structure in the image is modeled locally. In this paper, we propose a multi-scale conditional generative adversarial network based on attention mechanism, which can produce high resolution images to solve the numerical imbalance problem of chest X-ray image data. The network was able to produce images for various diseases by controlling condition variables with only one network. It's efficient and effective in that the network don't need to be learned independently for all disease classes and solves the problem of long distance dependency in image generation with self-attention mechanism.

• Journal of KIISE:Information Networking
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• v.36 no.6
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• pp.471-480
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• 2009

One of the principal impediments to the achievement of a scalable access control for a large number of subscribers in a public broadcast is to distribute key update messages reliably to all stateless receivers. However, in a public broadcast, the rekeying messages can be dropped or compromised during the transmission over an insecure broadcast channel, or transmitted to the receivers while it was off-line. In this study, we propose a novel group key management scheme that features a mechanism that allows the legitimate receivers to recover the current group key even if they lose key update messages for long-term sessions using short hint messages and member computation. The performance analysis result shows that the proposed scheme has advantages of the scalable and efficient rekeying compared with the previous reliable group key distribution schemes. The proposed key management scheme targets a conditional access system in a media broadcast where there is no feedback channel from receivers to the broadcasting station.