• 인터넷정보학회논문지
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• 제17권6호
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• pp.9-15
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• 2016

본 논문에서는 OTT(Over The Top)가 채널상태에 따라 동적으로 최적화함으로서, 최고의 비디오 비트율(bit-rate)로 전송하기 위한 스마트 HLS(HTTP Live Stream) 플랫폼을 제안하였다. HLS 플랫폼은 스마트 OTT가 채널변경 시간을 최적화도록 HLS 서버와 OTT 클라이언트 사이의 대역폭을 모니터링 한다. 이를 위해 다중 비트율과 적정한 대역폭으로 비디오 스트림을 조정하도록 설계되었다. 제안한 스마트 OTT는 최적의 비트율로 버퍼링을 함으로서 라이브와 VOD(Video On Demand)비디오를 재생할 수 있다. 이러한 HLS 플랫폼은 세그먼트 형식의 H.265 MPEG-2 TS(Transport Stream) 비디오와 관련 정보를 담고 있는 m3u8 파일과 스마트 OTT가 연동한다. 이로서 설계한 단일 버퍼링 기반의 스마트 OTT는 동작 중인 채널 대역폭 효율과 복호화된 VOD에 대한 적응적 비트율을 활용함으로서 대역폭이 허용하는 최대의 데이터를 버퍼링으로 최적의 비디오를 전송할 수 있다.

• Journal of electromagnetic engineering and science
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• 제5권3호
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• pp.122-125
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• 2005

This paper describes a design of a miniature patch antenna and its 4-channle array for 5.25 GHz wireless LAN band. Each patch element is designed for the low mutual coupling between each element and for the small size of the array antenna. The size of the each element is $7 mm{\times}14.5 mm{\times}5.6 mm$ and it satisfy IEEE 802.11a frequency band. It is arrayed for independent 4-channel operation. The total size of the array antenna is $35.6 mm{\times}52.5 mm{\times}5.6 mm$. The measured reflection coefficients and the radiation patterns of the fabricated antennas show the reasonable agreements with prediction.

• Journal of the Optical Society of Korea
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• 제6권4호
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• pp.141-164
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• 2002

A 42 channel demultiplexer for dense wavelength division multiplexing(WDM) using photopoly-mer volumetric diffraction grating that has excellent optical properties and low cost capability, has been designed and optically demonstrated. From the experimental results, we have obtained the 3 dB bandwidth of 0.18 nm, crosstalk suppression of 20 dB and channel uniformity of 1.6 dB for 50 GHB channel spacing.

• 한국방송∙미디어공학회:학술대회논문집
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• 한국방송공학회 1996년도 학술대회
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• pp.55-59
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• 1996

In this paper, we first analyze the influence of interference due to the time variation and delay spread of the mobile channel on an orthogonal frequency division multiplexing (OFDM) system. With the result, we obtain the bit error rate performance of the 16-QAM OFDM system. Second, we investigate the performance of the Reed-Solomon (RS) coded 16-QAM OFDM system when the number of subcarriers varies. In the investigation, we assume that the information transmission rate and the total bandwidth expansion due to coding, guard interval, and the number of subcarriers are fixed. Under this condition, it is observed that there are optimum numbers of subcarriers that minimize the post decoding symbol error probability of RS code for various channel states.

• 한국음향학회:학술대회논문집
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• 한국음향학회 1998년도 학술발표대회 논문집 제17권 1호
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• pp.357-360
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• 1998

DS/CDMA system rejected narrow-band interference and additional White Gaussian noise which are occured at multipath, intentional jammer and multiuser to share same bandwidth in mobile communication systems. Because of having not sufficiently obtained processing gain which is related to system performance, they were not effectively suppressed. In this paper, an matched filter channel model using backpropagation neural network based on complex multilayer perceptron is presented for suppressing interference of narrow-band of direct sequence spread spectrum receiver in DS/CDMA mobile communication systems. Recursive least square backpropagation algorithm with backpropagation error is used for fast convergence and better performance in matched filter receiver scheme. According to signal noise ratio and transmission power ratio, computer simulation results show that bit error ratio of matched filter using backpropagation neural network improved than that of RAKE receiver of direct sequence spread spectrum considering of con-channel and narrow-band interference.

• 한국위성정보통신학회논문지
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• 제12권4호
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• pp.166-169
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• 2017

This paper describes atmospheric phenomena and effects for satellite-to-ground laser communication channel. Satellite laser communication has advantages such as very high bandwidth, inherent security, robustness to electromagnetic interference, unlicensed frequency band. However, satellite laser communication is affected by various factors. Transmission quality is degraded by factors as system loss, geometric loss, misalignment loss, atmospheric loss. Atmospheric loss is major factor of performance degradation. In this paper, the atmospheric phenomena such as absorption, scattering and turbulence are discussed and analyzed for developing satellite laser channel model and laser transmission scheme robust to atmospheric phenomena.

• 한국초전도학회:학술대회논문집
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• 한국초전도학회 2000년도 High Temperature Superconductivity Vol.X
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• pp.169-172
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• 2000

We have constructed a multi-channel SQUID magnetometer system. The system is designed to operate normally with 10 high temperature direct coupled SQUIDs. The main features of the system include a remote control by serial communication, low noise with wide bandwidth and high slew rate by several MHz modulation, signal conditioning and calibration by digital signal processing.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 추계학술대회논문집A
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• pp.693-698
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• 2000

Aspects of classical information theory, such as rate distortion theory, investigate how to encode and decode information from an independently identically distributed source so that the asymptotic distortion rate between the source and its quantized representation is minimized. However, in most natural dynamics, the source state is highly corrupted by disturbances, and the measurement contains the noise. In recent coder-estimator sequence is developed for state estimation problem based on observations transmitted with finite communication capacity constraints. Unlike classical estimation problems where the observation is a continuous process corrupted by additive noises, the condition is that the observations must be coded and transmitted over a digital communication channel with finite capacity. However, coder-estimator sequence does not provide such a quantitative analysis as a variance for estimation error. In this paper, under the assumption that the estimation error is Gaussian distribution, a variance for coder-estimation sequence is proposed and its fitness is evaluated through simulations with a simple example.

• 대한전기학회논문지:시스템및제어부문D
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• 제50권8호
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• pp.400-405
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• 2001

Quadrature Amplitude Modulation(QAM) is well known a bandwidth efficient modulation scheme. However, its use for mobile communications has been limited due to noise and signal distortion. Recently, the QAM scheme is emerging as a new modulation scheme for a band-limited wireless system. In this paper, we propose an iterative decoding algorithm assuming QAM signal for a narrow-band mobile channel. The Algorithm is based on the EM(Expectation Maximization) Algorithm, and the performances of the proposed decoder are assessed using computer simulation. The simulation results show that the proposed decoder perform better compared to that of other schemes.

• 융합신호처리학회 학술대회논문집
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• 한국신호처리시스템학회 2001년도 하계 학술대회 논문집(KISPS SUMMER CONFERENCE 2001
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• pp.41-44
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• 2001

다중경로에 패스파에 의한 주파수 선택성 페이딩 이나 각종 전기적 잡음에 의한 통신로 상황이 변화하는 무선 통신 환경 하에서는 점유대역 내에서도 전송 특성이 상이하게 되므로 OFDM 전송방식에서는 서브 캐리어간 간섭이 발생한다. 또한 이러한 전송로에서는 인접 캐리어간에 직교성이 깨어지고 다중된 신호가 혼합되어 버림으로써 그 전송 특성이 급격히 저하 할 수 있다. 본 논문에서는 전송로 특성이 상이한 채널에 대해 케리어 군을 복수의 서브 밴드군으로 나누어 변조 방식을 선택하고 심볼율을 변화할 수 있는 대역 분할형 OFDM 시스템의 BER특성을 고찰하였다.