• The Journal of the Korea institute of electronic communication sciences
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• v.12 no.6
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• pp.1115-1120
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• 2017

In this paper, we apply the LMMSE(: Linear Minimum Mean Square Error) algorithm to overcome the Doppler effect according to the UAV(: Unmanned Aerial Vehicle) velocity in multipath fading channel environment. Simulation results show that the performance difference depends on the pilot arrangement and pattern, and we confirmed that the frame structure proposed in this paper can provide a stable secondary link for high speed UAV system.

• Proceedings of the IEEK Conference
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• 2002.07c
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• pp.1681-1684
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• 2002

A multilevel modulation with selectable constellations is adopted in the downlink subframe modulation of the IEEE 802.16 standard to increase the total throughput. One of the decision factors of the modulation is the location of SS(Subscriber Station) . Also, for the 802.16, low phase noise of local oscillator is needed due to high operating frequency and severe loss in the propagation channel. We investigate the BER of down-link subframe with the phase jitter under the standard's specified LOS(line of sight) and multipath environment with randomly generated SS locations. Simulation results show BER performance degradation for the modulation corresponding to selected constellations and additionally required SNR to achieve 10$\^$-3/ BER under various phase jitter.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.5 no.2
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• pp.263-268
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• 2001

This paper analyzes error probability performance adopted the Ray Tracing method efficiently analyzing millimeter wave or optic wave in Inter Vehicle Communication(IVC). Analysis environment analyzed bit error characteristic in 60㎓ band with very powerful to multipath wave, to be large to oxygen absorption and to be good to frequency reuse efficiency. We analyzed bit error characteristic of DS/CDMA system by multi access user in Two-Ray rician channel adopted reflect wave of grand, reflect wave of concrete wall and reflect wave of driving vehicle at side road. Improvement performance is adopted MRC diversity.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.4
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• pp.817-823
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• 2010

MC-DS-CDMA is technique where a single data symbol is transmitted at multiple subcarriers which are orthogonal to each other. With this technique, frequency diversity can be achieved. The performance of PSAM MC-DS-CDMA system with the application of MRRC antenna diversity is analyzed. The BER performance of this system over multipath fading environment is evaluated, considering the channel estimation error, carrier frequency offset, and the nonlinear high power amplifier.

• The Journal of the Acoustical Society of Korea
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• v.17 no.8
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• pp.64-67
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• 1998

여러 해 동안 많은 연구자들에 의해서 코히런트한 간섭신호가 있는 환경에서 신호 의 도래각을 추정하는 방법에 대한 연구가 진행 되어왔다. 이런 방법들은 대부분 공간 평활 (Spatial Smoothing)류의 방법을 사용하고 있으나 Pillai에 의해서 각 센서에 들어오는 신호 의 평균을 이용한 방법이 제안되었다. 이 방법에서는 특별히 복소수의 입력에 대해서는 대 칭형 배열을 사용하도록 했기 때문에 실수 입력을 다룰 때 보다 약 2배의 센서 개수가 필요 하다[S.U.Pillai,Array Signal Processing,Springer-Verlang New York, 1989]. 본 논문에서는 Pillai의 방법을 사용할 때 복소수 입력에서도 실수 입력의 경우와 같은 개수의 센서를 사용 하는 방법을 제안한다.

• Proceedings of the Acoustical Society of Korea Conference
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• autumn
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• pp.277-280
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• 2000

수중환경에서 표적의 탐지 성능을 향상시키기 위하여 능동 소나에서는 높은 시간-대역폭곱의 파형들을 사용하며 대표적인 것으로 LFM 펄스를 들 수 있다 LFM 펄스를 사용하여 표적까지의 거리와 표적의 속도를 추정하는 방법으로는 모호함수를 사용하는 방법과 deconvolution 방법 및 FR-기반 기법 등이 있다. 이러한 기법중 모호함수 사용 방법과 deconvolution 방법은 능동 소나의 운용 주파수 대역에서 많은 연산량이 요구되므로 실제 시스템에 적용하기에는 제약을 받는다. 그리고 다른 기법에 비해 적은 연산량을 가지는 FFT-기반 상관관계 기법은 실제 시스템에 적용이 가능하지만 다중경로에 의한 성능 저하를 가지고 있다. 본 논문에서는 적은 연산량을 가지는 FFT-기반 기법을 보완하여 다중경로에 적용 가능한 새로운 탐지기를 제안한다.

• Journal of the Korea Society of Computer and Information
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• v.4 no.3
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• pp.101-106
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• 1999

Many of study to progress in order to increase of capacity system and multiple access interference to mobile communication environment. In this paper, a proposal to differently processor smart antenna of beamforming technique in spatial processor and rake receiver in the time processor. The performace of DS/CDMA system to multipath fading channel using to beamforming techinque.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.10A
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• pp.1486-1491
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• 2000

A Multicarrier system required a lower speed paralled-type of signal processing in contrast to a fast serial processing in a single carrier CDMA system. For the analysis we evaluate MC-CDMA system performance with that of a single-carrier CDMA system and a multi-carrier CDMA system based on the various jamming conditions. Also we studied to the capacity level against the threat environment through the performance comparison in commercial CDMA system and Limiting repeater system. as a result we found that M-CDMA system has a robustness to narrowband interference and multipath environments like as a Rayleigh fading.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• v.9 no.1
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• pp.217-220
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• 2005

무선 다중경로 채널에서 데이터를 고속으로 전송할 경우, 신호는 페이딩, ISI(inter-symbol interfrence) 등의 영향으로 높은 에러율을 가지게 된다. 현재의 DSRC 시스템은 1Mbps 이상의 데이터 서비스가 어려울 것으로 예상되므로 개선된 변복조방식이 요구된다. OFDM(orthogonal frequency division multiplexing) 방식은 보호기간의 삽입을 통하여 ISI를 방지할 수 있으므로 고속 데이터 전송에 적합하다. 따라서 본 논문에서는 다중경로 페이딩 환경에서 시뮬레이션을 통하여 12 Mbps 전송 속도를 갖는 OFDM/QPSK 통신 시스템의 BER 성능을 비교${\cdot}$분석하고 다중경로 페이딩 환경에서 채널 상태를 추정 보상하기 위하여 판정 궤환경 등화기(Decision Feedback Equalizer)를 적용하여 시스템 성능을 개선하였다.

• Journal of Electrical Engineering and Technology
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• v.13 no.3
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• pp.1363-1370
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• 2018

In visible light (VL) positioning based on angle of arrival (AOA) estimation for smart indoor service, the AOA parameters obtained at the receiver has sometimes a random and distributed angle form instead of a point angle form due to the multipath transfer of the actual visible light and short positioning distance. The AOA estimation of a VL signal with a random and parametric distributed angle form may give incorrect AOA parameter estimates, which may result in poor VL positioning performance. In this paper, we classify the AOA parameters of the received VL signal into three forms according to the actual positioning channel environment and consider the short-range VL positioning method. We propose a subspace-based AOA parameter estimation technique and a data fusion method, and analyzed the proposed method by simulation and the measurement of the real VL channel characteristics.