• Journal of the Institute of Electronics Engineers of Korea TC
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• v.45 no.2
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• pp.67-74
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• 2008

This paper proposes two peak-windowing algorithms for peak-to-average power reduction(PAPR) of orthogonal frequency division multiple access(OFDMA) downlink systems. The Proposed algorithms mitigate the effect of excessive suppression due to successive peaks or relatively high peaks of the signal. First, multi-stage peak windowing algorithm is proposed, which exploits multiple threshold of target PAPR in order to step down the peaks gradually. Secondary, variable-length peak windowing algorithm is proposed, which adapts the window length with respect to the existence of successive peaks within a half of window length. Therefore, the proposed method reduces the distortion of signal amplitude caused by window overlapping. The proposed algorithms outperform the conventional peak windowing with the aid of window-length adaptation or sequential peak power reduction. Simulation results show the efficiency of the proposed algorithms over OFDMA downlink systems, especially WiBro systems.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2011.07a
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• pp.462-465
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• 2011

본 논문에서는 다중 반송파, 특히 OFDM 시스템의 PAPR 을 감소시킬 수 있는 CFR 알고리즘을 다룬다. 기존의 피크 윈도윙 기법이 윈도우 길이 내에 피크들이 여러 개 있을 경우, 과도 clipping 으로 인하여 성능이 열화되는 현상을 개선하기 위하여 포락선 기반 피크 윈도윙 기법을 적용한다. 뿐만 아니라, 피크 윈도윙이 가지고 있는 EVM 열화를 완화하기 위하여 기존의 단순 clipping 기법과 혼합하여 시스템에서 요구하는 EVM 성능뿐 아니라 ACLR 성능까지도 만족하도록 한다. MATLAB 을 이용하여 알고리즘을 검증하고, 하드웨어 구현을 위하여 Xilinx Virtex5 를 이용하여 검증하여 제안하는 기법의 복잡도는 높지만 EVM 과 ACLR 성능이 우수함을 알 수 있다. 효율적인 주파수 이용과 수신 성능 측면에서 우수한 성능을 보인다. 따라서 DVB-T 나 LTE, IEEE 802.16m 등의 차세대 방송 및 통신의 전송에 이용되는 OFDM 신호의 PAPR 을 효과적으로 줄일 수 있는 기법으로 적용될 수 있다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.20 no.5
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• pp.963-971
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• 2016

This paper is a research of gaze analysis for measuring task switching behavior at multiple windows in GUI of windowing system. Previous methods that define area of interest for categorizing gaze had difficulties to define dynamic content that disappears or changes over time. On the other hand, this study suggests a new method to categorize gaze that defines Area of interest in a unit of window during the eye tracking experiment. In this paper, we constructed the conception of WOI(Window of Interest) in GUI of windowing system. Therefore, we developed a system using an eye tracker device and implemented a number of experiments. In addition, we analyzed the number of task switching and proportion of watched content. The method in the study comprehend from previous researches as it can measure and analyze the multi-tasking behaviors using multiple numbers of windows.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.9A
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• pp.871-877
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• 2007

In this paper, we propose a new transmit diversity scheme using window functions in orthogonal frequency division multiplexing (OFDM) system. Transmit diversity of the scheme is varied with window functions and the condition of the window function to maximize transmit diversity is derived. The proposed scheme can be considered as a generalization of the diversity schemes such as cyclic delay diversity (CDD), orthogonal transmit diversity (OTD), and frequency switched transmit diversity (FSTD).

• Journal of the Institute of Electronics and Information Engineers
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• v.54 no.2
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• pp.146-150
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• 2017

In OFDM system, the out-of-band radiation of ensemble interferes with the adjacent ensemble and result in the reduction of receiving performance. So the reduction scheme of out-of-band radiation is very important. In this paper, a time-domain windowing method to reduce the out-of-band radiation is considered to DAB systems. We adopt the considered method to T-DMB(DAB mode-1) and AT-DMB Systems, and we get about 3-dB gains of out-of-band radiation. And also we show that the considered method doesn't reduce the BER performance.