• 대한전기학회:학술대회논문집
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• 대한전기학회 2008년도 학술대회 논문집 정보 및 제어부문
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• pp.390-391
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• 2008

대용량의 이동 고속통신 환경 하 에서 다중경로 페이딩에 의한 성능열화 영향을 효과적으로 줄이고, 용량을 극대화하기 위해 MIMO(Multi-Input Multi-Output) 와 OFDM (Orthogonal Frequency Division Multiplexing) 기술들이 차세대 이동통신시스템으로 최근에 각광을 받고 있다. 그러나 cellular 시스템에서는 Co-Channel Interference의 영향을 피할 수도 없으며, 그 영향 또한 그 무엇보다도 크다. 그러므로 본 논문에서는 이러한 MIMO OFDM 시스템의 Co-Channel Interference 의 영향을 줄이고 성능 향상을 위해 Interference Cancelling 기법을 응용한 STBC-OFDM 시스템의 성능을 MATLAB simulation을 통해 기술하였다.

• 한국정보통신설비학회:학술대회논문집
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• 한국정보통신설비학회 2007년도 학술대회
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• pp.89-91
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• 2007

Multimedia service based on interactivity, personalization, multiple channels and community distinguishes IPTV from incumbent TV. But data encoding/decoding time and image frame processing should be considered in digital TV versus analog device. Especially channel zapping time is one of the most important parameters for the service quality of IPTV. This paper proposes the mechanism for decreasing the channel zapping time with multiple decoder and image frame processing. We also implemented the multi-group video community service system using IP multicasting function supporting interactive learning service.

• IEIE Transactions on Smart Processing and Computing
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• 제3권1호
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• pp.35-39
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• 2014

This paper proposes a Modified Minimum Mean Square Error (M-MMSE) estimator for an Orthogonal Frequency Division Multiplexing (OFDM) System over fast fading Rayleigh channel. The proposed M-MMSE estimator considered the effects of the efficient placement of pilots based on the channel energy distribution. The pilot symbols were placed in a non-linear manner according to the density of the channel energy. Comparative analysis of the MMSE estimator for a comb-type pilot arrangement and M-MMSE estimator for the proposed pilot insertion scheme revealed significant performance improvement of the M-MMSE estimator over the MMSE estimator.

• Journal of Communications and Networks
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• 제10권2호
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• pp.127-136
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• 2008

For mobile wireless systems with full frequency reuse, co-channel interference near the cell coverage boundaries has a significant impact on the signal reception performance. This paper addresses an approach to efficiently mitigate the effect of downlink co-channel interference when multi-antenna terminals are used in cellular environments, by proposing a signal detection strategy combined with a system-level coordination for dynamic frequency reuse. We demonstrate the utilization of multi-antennas to perform spatial demultiplexing of both the desired signal and interfering signals from adjacent cells results in significant improvement of spectral efficiency compared to the maximal ratio combining (MRC) performance, especially when an appropriate frequency reuse based on the traffic loading condition is coordinated among cells. Both analytic expressions for the capacity and experimental results using the adaptive modulation and coding (AMC) are used to confirm the performance gain. The robustness of the proposed scheme against varying operational conditions such as the channel estimation error and shadowing effects are also verified by simulation results.

• 대한전자공학회논문지
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• 제21권1호
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• pp.71-78
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• 1984

본 논문에서는 ADPCM 시스템의 noisy channel에서의 성능 개선을 위한 새로운 방법을 제시하였다. 이 방법은 robust quantiser를 사용하면서 주기적으로 maximum step sixte를 수신측에 보내준다. 또한 수신측 버퍼에서는 MSB 에러검출·수정을 행한다. Noisy channel 상태에서 실제의 음성에 대해 컴퓨터 시뮬레이션한 결과 제안된 시스템의 성능은 원래의 ADPCM의 성능보다 크게 향상되었다.

• 한국수자원학회논문집
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• 제30권1호
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• pp.15-22
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• 1997

하천형성의 중요한 요인이 되는 사행하천의 흐름은 막곡호안에 많은 영향을 준다. 특정한 하천에 대해 하도개량을 적용시키기 위한 일반적인 기준을 기술하기는 어려우나 토목 설계자에게 어떤 원칙과 지침을 제공하는 것은 대단히 중요하다. 본 고정상 실험연구의 목적은 평균유속과 유로만곡부에서의 곡률변경으로 최대 유속의 크기를 구하여 매번의 수리모형실험을 실시하지 않고도 중소하천의 개수에 이용할 수 있는 자료를 제공함에 있다.

• Journal of information and communication convergence engineering
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• 제14권4호
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• pp.227-232
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• 2016

In this study, the performance of a 32-quadrature amplitude position modulation (QAPM) system is analyzed under a Rician fading channel condition when the maximal ratio combining (MRC) diversity technique is used in the receiver. The fading channel is modeled as a frequency non-selective slow Rician fading channel corrupted by additive white Gaussian noise (AWGN). QAPM is available to improve BER performance without amplifying transmit power, and MRC diversity makes the performance improvement of QAPM system even bigger by intentionally maximizing SNR. Error performances are shown for the 32-QAPM system and a 32-phase silence shift keying (PSSK) system in order to examine the effects of fading severity, for various values of the Rician parameter, K. The dependence of error rates on MRC diversity is also analyzed. The simulation results show that the BER performance of the 32-QAPM system is better than that of the 32-PSSK system under the above mentioned conditions.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2005년도 International Meeting on Information Displayvol.I
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• pp.289-292
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• 2005

New poly-Si TFTs have been proposed and fabricated in order to increases the output channel resistance ($r_o$). The counter-doped($p^+$) source is tied to the $n^+$ source and is extended into the channel region so that it employs the reverse bias depletion in the channel. As $V_{DS}$ is increased, the depletion width is increased and the effective channel width is reduced. Therefore, the output current saturates well and the $r_o$ is increased successfully. The proposed CMOS devices may improve the amplifier gain of data driver in active-matrix displays

• 한국통신학회논문지
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• 제29권3A호
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• pp.257-265
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• 2004

MRC 다이버시티 수신 시스템에서 상호 독립적이고 동일한 전력을 갖는 동일 채널 간섭자들이 존재할 경우, Gray 부호화된 임의 직사각 QAM 신호의 성능을 분석하였다. 본 논문에서는 L개의 수신안테나를 갖는 MRC 수신 다이버시티 시스템에서 N명의 서로 독립적이고 동일한 나카가미 분포를 갖는 동일 채널 간섭자들의 신호가 수신되는 경우의 폐쇄형 (closed-form) 평균 비트 오류 확률 수식을 유도하였다. 이 수식은 수치 계산에 의해 쉽게 계산되는 초기하 함수를 이용하여 표현되었다.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2002년도 ITC-CSCC -3
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• pp.1447-1450
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• 2002

In this paper, we propose a new access method named UR (Use. Relay) scheme to improve the channel efficiency in mobile communications. In UR scheme, packets of a data terminal that do not demand real time communications are relayed by other terminals during their inactive periods, which ue communicating with the base station through a fixed channel at that time. Simulation results show that with UR scheme, the blocking probability md the throughput are improved considerably with an allowable increase in the average delay.