• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.26 no.9
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• pp.806-813
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• 2015

In order to satisfy several conditions with respect to size, weight, and costs, automotive radars use an antenna consisting of a small number of receiving channels. If RELAX technique is applied to the automotive radars, angles of targets located in antenna beam can be estimated as well as the number of the targets. However, a small number of receiving channels in the antenna leads to inaccurate spectral estimation in angle domain, which in turn degrades performance of RELAX technique. Therefore, in this study, root-MUSIC technique coupled with MDL criterion is introduced to decide accurate angles of targets in antenna beam. In simulations, we show superior performance of proposed scheme using simulation results when three point targets are located in antenna beam.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.7
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• pp.1257-1265
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• 2015

In this paper, we describe a greedy user selection scheme for multiuser multiple-input multiple-output (MIMO) systems. We propose a new metric which has significantly improved performance compared to the Frobenius norm metric. The approximation of projection matrix is applied to increase the accuracy of Frobenius norm of effective channel matrix. We analyze the computational complexity of two metrics by using flop counts, and also verify the achievable sum rate through numerical simulation. Our simulation result shows that the proposed metric can achieve the improved sum rate as the number of user antenna increases.

• 정보화사회
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• s.13
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• pp.32-35
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• 1988

정보통신회선 사용제도가 대폭적으로 개선되었다. 그동안 협회가 “민간 VAN활성화 방안의 연구”, “전기통신 관계법령 정비에 관한 워크샾”. “공중전기통신사업 개정안에 대한 공청회” 등의 활동을 통해 회원사들의 요구사항을 수렴. 집약하여 체신부로 하여금 현행의 불합리한 회선사용의 제한을 완화토록 누차에 걸쳐 촉구한 결과 이번 개선조치를 얻어냈다. 이번 조치는 지난 1일 협회 법제분과위원회 석상에서 정부당국자에 의해 최초로 발표되어 회의참석자(회원사 임직원) 모두로부터 전폭적인 환영을 받았다. 특히 이제까지 그룹 VAN에만 허용하던 정보의 교환행위를 중소기업 대상 전산망 서비스분야까지 확대 허용한 점, 다중화 장치 접속 허용, 긴밀관계자 인정범위 확대 등의 내용은 업계측을 크게 고무하고 정보통신사업의 활성화를 촉진하는 획기적인 조치라는 것이 중평이다. 아울러 중소기업기본법 제2조의 기중에 관련한 확대허용 조치는 자칫 대규모 VAN업체에 대한 영세 S/W 업체들의 자본적, 기술적 예속을 가속화시킬 가능성을 잉태하고 있어 이들에 대한 육성.지원대책을 서둘러야 할 때임을 암시하고 있다. 이번 조치에 따라 체신부는 ‘89.1.1일자 시행을 목표로 공중통신사업자로 하여금 다중화장치 접속기준을 제정토록 지침을 하달한 것으로 알려졌다. 한편, 정부는 국내 정보통신사업 육성방안에 대한 연구.검토와 함께 전기통신관련법령의 전면적인 개편을 추진키 위해 이미 전문연구기관단체 등에 연구용역을 주는 등 본격적인 준비작업에 들어갔다.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.33 no.1
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• pp.31-43
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• 2015

This study had been aimed to conduct the camera calibration on VLBI antenna in the Space Geodetic Observation Center of Sejong City with a low-cost digital camera, which embedded in a mobile phone to determine the three-dimension position coordinates of the VLBI antenna, based on stereo images. The initial values for the camera calibration have been obtained by utilizing the Direct Linear Transformation algorithm and the commercial digital photogrammetry system, PhotoModeler $Scanner^{(R)}$ ver. 6.0, respectively. The accuracy of camera calibration results was compared with that the camera calibration results, acquired by a bundle adjustment with nonlinear collinearity condition equation. Although two methods showed significant differences in the initial value, the final calibration demonstrated the consistent results whichever methods had been performed for obtaining the initial value. Furthermore, those three-dimensional coordinates of feature points of the VLBI antenna were respectively calculated using the camera calibration by the two methods to be compared with the reference coordinates obtained from a total station. In fact, both methods have resulted out a same standard deviation of $X=0.004{\pm}0.010m$, $Y=0.001{\pm}0.015m$, $Z=0.009{\pm}0.017m$, that of showing a high degree of accuracy in centimeters. From the result, we can conclude that a mobile phone camera opens up the way for a variety of image processing studies, such as 3D reconstruction from images captured.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.2C
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• pp.86-92
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• 2011

This paper details the downlink performance analysis of an multiple antennas system that combines adaptive beamforming and spatial multiplexing (SM) Multiple Input Multiple Output (MIMO). The combination of MIMO signal processing with adaptive beamforming is applied to WiBro, the South Korean Orthogonal Frequency Division Multiple Access (OFDMA) system that follows the IEEE 802.16e standard. Performance analysis is based on the results of experiments and simulations obtained from a fixed-point simulation testbed. Simulations demonstrate that the MIMO Beamforming OFDMA system improves the required signal to noise ratio (SNR) over the conventional MIMO OFDMA system by 3 dB (QPSK) / 2.5 dB (16-QAM) for the frame error rate (FER) of 1% in the WiBro signal environments. From the implementation of the fixed-point simulation testbed and its experimental results, we verify the feasibility of the MIMO Beamforming technology for realizing a practical WiBro base station.