• Journal of IKEEE
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• v.20 no.1
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• pp.1-8
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• 2016

In this paper, we propose an effective time-of-arrival (TOA)-based localization method with adaptive bias computation in indoor environments. The goal of the localization is to estimate an accurate target's location in wireless localization system. However, in indoor environments, non-line-of-sight (NLOS) errors block the signal propagation between target device and base station. The NLOS errors have significant effects on ranging between two devices for wireless localization. In TOA-based localization, finding the target's location inside the overlapped area in the TOA-circles is difficult. We present an effective localization method using compensated distance with adaptive bias computation. The proposed method is possible for the target's location to estimate an accurate location in the overlapped area using the measured distances with subtracted adaptive bias. Through localization experiments in indoor environments, estimation error is reduced comparing to the conventional localization methods.

• The Bulletin of The Korean Astronomical Society
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• v.43 no.2
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• pp.43.2-43.2
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• 2018

The line-of-sight component in the relative motion of galaxy pairs sources the redshift space distortion (RSD) in galaxy surveys. By knowing the probability density function (PDF) of pair-wise motions and projecting it to the line-of-sight direction, one can compute the RSD effect precisely. I present the pair-velocity PDF of dark matter and galaxies in the Horizon-run 4 simulation. I also derive a model motivated by the perturbation theory which fits the results fairly well. I also discuss the application of the model in constraining the cosmology.

• 제어로봇시스템학회:학술대회논문집
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• 1996.10b
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• pp.245-248
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• 1996

This paper suggests a new concept for missile guidance control, called linearized common curvature guidance law that enhances the probability to kill a target. The proposed guidance system is composed of two switching modes; one for the midcourse guidance and the other for the terminal guidance, which is switched by a specified critical value (.epsilon.). And the system and the commands are formulated and its simulations are provided in comparison with the conventional commanded line of sight guidance algorithm. Miss distance and angle of attack are denoted as performance of parameters. This new concept, common curvature guidance algorithm, revises the navigation guidance and accompanies, various considerations.

• 제어로봇시스템학회:학술대회논문집
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• 1989.10a
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• pp.93-98
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• 1989

This paper describes the application of the recently developed feedback linearization technique to designing a new Command to Line-of-Sight (CLOS) guidance law. We show that the CLOS guidance problem can be formulated as a tracking problem. Then, using the feedback input-output linearization technique, we find a new 3dimensional CLOS guidance law that can assure zero miss distance for a randomly maneuvering target. It sheds light on the feedforward acceleration compensation terms used in the conventional CLOS guidance laws to improve the performance. To illustrate further the significance of our result, simulation results are given.

• Proceedings of the Korean Information Science Society Conference
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• 2005.11b
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• pp.610-612
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• 2005

사용자의 환경정보(Context)는 기존 서비스나 정보 검색을 효과적으로 하기위해 이용되고 있다. 이러한 환경정보중의 사용자 위치정보는 많은 어플리케이션이나 연구에서 유용하게 사용되고 있다. 이미 많은 연구에서 사용자의 위치를 인식하기 위해서 다양한 기술을 이용한 방법을 제안했다. 하지만 기존 연구들은 특정 환경기반 시나리오를 기반으로 개발해서 다양한 위치정보를 필요로 하는 위치기반 서비스를 제공하기 어렵다는 단점이 있다. 본 논문에서는 이러한 문제를 해결하기 위해서 IrDA(Infrared Data Association)의 Line of Sight 통신 특성을 이용하는 방법을 제안한다. 또한 위치인식 시스템의 유효성을 보여주기 위한 방법으로 "박물정보 제공 서비스"를 프로토타입으로 구현하였다.

• Journal of Aerospace System Engineering
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• v.2 no.1
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• pp.13-16
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• 2008

The line of sight(LOS) is affected by the vibration of spacecraft. It is necessary to predict the effect of disturbance on LOS stability. Reaction wheel assembly is anticipated to be the largest disturbance source on spacecraft. The disturbance which is occurred mainly due to the mass imbalance is analyzed with harmonic numbers. The accuracy and stability are verified by probability density function with dynamic equation of the satellite motion.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2013.10a
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• pp.609-611
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• 2013

There's little to obstacles obstructing communication in the sky. There are nearly fixed obstacles obstructing communication on the ground. But communication disruption can be occur frequently and unexpectedly on the sea surface. Especially, it is difficult for a small station which can be greatly affected by waves and low antenna height to secure the LOS for radio communication. In this paper, LOS and minimum antenna height is calculated due to changing wave height and Tx/Rx antenna height on the sea surface.

• 제어로봇시스템학회:학술대회논문집
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• 2001.10a
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• pp.58-58
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• 2001

This paper shows a practical approach that is robust to the errors causing path-delay in mobile wireless location, and analyzes its performance by comparing with other methods. NLOS(non-line-of-sight) error and multipath are two big sources of positioning error in wireless location. Contrary to GPS(global positioning system), they result from the terrestrial propagation of a signal. Especially, since LOS(line-of-sight) path between a transceiver and a receiver is blocked by intermediate buildings and topography, NLOS causes a signal to be reflected and diffracted. This path-delay error is very localized, and so, it is not easy to be estimated and mitigated. To treat such localized error, therefore ...

• Proceedings of the IEEK Conference
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• 2003.07a
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• pp.298-301
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• 2003

본 논문에서는 2.4 [GHz] 대역에서 1(equation omitted)2 마이크로스트림 배열 안테나를 이용한 지하철 터널내의 전파특성을 고찰하였다. 445 [m]의 터널구간에서 협대역 측정결과 LOS (Line-of-Sight)구간에 비하여 NLOS(Non-Line-of-Sight)구간에서는 수신 전력 레벨이 급격히 감소 하였으며, 10단 길이의 PN Sequence를 이용한 광대역 채널 측정에서는 Fan Beam의 평균과도지연과 RMS 지연확산이 각각 3.5736 [ns]과 11.7327 [ns]로서 원편파와 지향성 빔에 비하여 우수함을 확인하였다. 또한 전체 측정구간에 대한 평균과도지연과 RMS 지연확산의 중간값과 표준편차를 구하였고 각각의 빔에 대하여 비교하였다.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2002.11a
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• pp.127-131
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• 2002

This paper presents the a measured path-loss characteristics in urban line-of-sight(LOS) and non line-of-sight(NLOS) environments for 3.4, 5.3, and 6.4 ㎓ band signals. A two-ray model is applied to analyse the path-loss characteristics in LOS areas. In LOS areas, an empirical break point, whose distance is shorter than a theorical break point, is founded. Further, a sudden power level drop occurs at a transition point from LOS region to NLOS area and different path-loss exponents are occured various cases. The power level drop due to comer loss and path-loss exponents both increase as the distance between the transmitter and the corner increases.