• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
• /
• 1992.11a
• /
• pp.25-29
• /
• 1992

In this paper, The Monte Carlo Simulation is performed in complex geometries which are composed of obstacles intercepted path of photon. Light is assumed to be particle and has particular direction and weighting value. The illuminance distribution is calculated proportional to the summation of weighting values striking area element. The result of simulation is consistent with that of experiments in a few error.

• 한국정보통신설비학회:학술대회논문집
• /
• 2007.08a
• /
• pp.440-444
• /
• 2007

As the mobile communication service is widely used, the demand for wireless repeaters is rapidly increasing because of the easiness of extending service areas. But a wireless repeater has a problem that the output of the transmit antenna is partially fed back to the receive antenna, which results in feedback interference. In this paper, we propose a new varable step-size LMS algorithm, which utilizes correlation between reference and error signals to adjust the step sizes, for cancelling the feedback interference signals in the WCDMA repeater under time-varying multi-path channels. The proposed algorithm was investigated through computer simualation by being applied to the time-varying channels. The simulation results demonstrated that the proposed one is superior to the conventional ones in terms of cancelation perormance.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.8 no.8
• /
• pp.1626-1631
• /
• 2004

OFDM are digital modulation techniques 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 OFDM systems with various antenna structure are analyzed, where data is transmitted over multi-path Rayleigh fading channel. The performance of this technique, gauged by the average bit error rate, is analyzed for the OFDM systems dependent upon the various antenna diversities.

• IE interfaces
• /
• v.12 no.3
• /
• pp.401-405
• /
• 1999

We present a simulation model to generate the spatial distribution of mobiles in cellular communication network. Three types of spatial distributions are considered; biased, random, and ratio-based distributions. This study also points out and corrects the critical errors performed by Das and Morgera(1997) in getting random location of mobiles. By applying a simple path loss model, the effects of our correction on the signal-to-interference(SIR) ratio are discussed. The numerical results indicate that the variation of SIR in the Das's biased distribution is larger than that of other distributions. As compared with the random distribution, the average SIR error of the biased distribution is 91.1%.

• Journal of Korean Institute of Industrial Engineers
• /
• v.22 no.2
• /
• pp.303-311
• /
• 1996

The Self Healing Ring (SHR) is one of the most Intriguing schemes which provide survivability for telecommunication networks. To design a cost effective SONET ring it is necessary to consider load balancing problems by which the link capacity is determined. The load balancing problem in SONET ring when demand splitting is not allowed is considered in this paper. An efficient algorithm is presented which provides the best solution starting from various Initial solutions. The initial solution is obtained by routing ell demands such that no demands pass through an are In the ring. The proposed algorithm iteratively improves the Initial solution by examining each demand and selecting the maximum load are in its path. The demand whose maximum arc load is biggest is selected to be routed in opposite direction. Computational results show that the proposed algorithm is excellent both in the solution quality and in the computational time requirement. The average error bound of the algorithm is 0.11% of the optimum and compared to dual-ascent approach which has good computational results than other heuristics.

• Proceedings of the Korea Multimedia Society Conference
• /
• 2001.06a
• /
• pp.307-311
• /
• 2001

신속조형시스템(RP : Rapid Prototyping)용 자료교환 표준인 STL의 자료구조는 단순하고, 조형용 2차원 단면 자료로의 전환이 용이하며, 생산 가공 기술로서의 현대적인 특성(신속성, 조형성, 경제성, 청정성 등)을 가지고 이는 장점이 있는 반면에, STL 3D 좌표값의 기준(좌표계의 원점)이 되는 크기 정보가 없다. 이런 문제를 구현된 STL 뷰어에서는, 스케일링(scaling) 기법과 선형적인 이동 기법을 사용하여 해결하였고, CAD 시스템으로 제작된 파일 자체의 문제점 패싯(facet) 중복, 정밀도, 법선 벡터 값의 오류 등도 검증기(verifier)와 오류 정정기(error corrector)글 구현하여 해결하였다. 제안된 방법으로 구현된 STL 뷰어는 시스템의 안정성과 확장성, 그리고 효율성 측면에서 우수한 성능을 보였으며, 슬라이싱(slicing), 경로 추적기(path tracer)의 전처리기의 역할을 한다.

• 제어로봇시스템학회:학술대회논문집
• /
• 1996.10b
• /
• pp.445-448
• /
• 1996

For a lightly damped system, IIR based filter can have better performance than FIR filter as an adaptive filter in ANC algorithm. IIR based filter which has an infinite impulse response can model a lightly damped acoustic system with a small number of weights compared that of FIR filter and has no nonlinearity and instability problems on weight updating process which are associated to the conventional IIR filters. There are, however, some drawbacks such as design parameters to be determined earlier to get better performance and much increased computational power especially in the presence of error path. In this study, base filter parameters are determined in systematic manner, with the knowledge of the nominal impulse response of the system which should be identified, by Prony's method. Three methods reducing the computational load are proposed and their performance and application limits are discussed. Simulation and experimental results demonstrate the feasibility of the proposed method.

• 제어로봇시스템학회:학술대회논문집
• /
• 2005.06a
• /
• pp.941-946
• /
• 2005

In this paper an active random noise control using adaptive learning rate neural networks is presented. The adaptive learning rate strategy increases the learning rate by a small constant if the current partial derivative of the objective function with respect to the weight and the exponential average of the previous derivatives have the same sign, otherwise the learning rate is decreased by a proportion of its value. The use of an adaptive learning rate attempts to keep the learning step size as large as possible without leading to oscillation. It is expected that a cost function minimize rapidly and training time is decreased. Numerical simulations and experiments of active random noise control with the transfer function of the error path will be performed, to validate the convergence properties of the adaptive learning rate Neural Networks. Control results show that adaptive learning rate Neural Networks control structure can outperform linear controllers and conventional neural network controller for the active random noise control.

• Journal of Institute of Control, Robotics and Systems
• /
• v.17 no.2
• /
• pp.108-115
• /
• 2011

This paper describes a new sensor system for mobile robot motion estimation using stereo infrared light sources and a camera. Visibility is being applied to robotic obstacle avoidance path planning and localization. Using simple visibility computation, the environment is partitioned into many visibility sectors. Based on the recognized edges, the sector a robot belongs to is identified and this greatly reduces the search area for localization. Geometric modeling of the vision system enables the estimation of the characteristic pixel position with respect to the robot movement. Finite difference analysis is used for incremental movement and the error sources are investigated. With two characteristic points in the image such as vertices, the robot position and orientation are successfully estimated.

• Proceedings of the IEEK Conference
• /
• 1998.06a
• /
• pp.38-41
• /
• 1998

Due to the increasing demand to multimedia services over wireless communication network, LMDS(Local Multipoint Distribution Service) has been proposed as an alternate approach for broadband wireless access network. But LMDS, Which uses the mmwavelength radio spectrum, has been limited for unknown microwave frequency characteristics. In this paper, we analyze the parameters related to the system design on 28GHz frequency: Propagation path loss and rainfall attenuation. Based on these analytical results, the proper cell size in Korea is determined. We also analyze the bit error rate and frame loss rate for various kinds of digital modulation schemes(QAM 4, 16, 64, 256). Finally, we apply to ㅍ service to evaluate a call blocking rate, efficiency and channel capacity.