• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2004.05a
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• pp.20-23
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• 2004

In non-selective frequency environment, it is difficult to take the advantage of path diversity. In the literature, some methods have been proposed to solve the issue. This paper presents a new method to obtain the resolvable path in Indoor Multi-carrier Code Division Multiple Access (MC-CDMA) system by using downlink beam forming. With the aid of downlink beamforming, the most reliable path is found and chosen for the communication link. The new approach is evaluated in term of bit error rate (BER) and power consumption. The simulation results show that the new approach can get better BER performance. However, the cost of BER improvement is a small degradation in power reservation.

• Spatial Information Research
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• v.19 no.1
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• pp.83-91
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• 2011

The route finding analysis is an essential geo-related decision support tool in a LBS(Location based Services) and previous researches related to route guidance have been mainly focused on route guidances for vehicles. However, due to the recent spread of personal computing devices such as PDA, PMP and smart phone, route guidance for pedestrians have been increasingly in demand. The pedestrian route guidance is different from vehicle route guidance because pedestrians are affected more surrounding environment than vehicles. Therefore, pedestrian path finding needs considerations of factors affecting walking. This paper aimed to extract factors affecting walking and charting the factors for application factors affecting walking to pedestrian path finding. In this paper, we found various factors about environment of road for pedestrian and extract the factors affecting walking. Factors affecting walking consist of 4 categories traffic, sidewalk, network, safety facility. We calculated weights about each factor using analytic hierarchy process (AHP). Based on weights we calculated scores about each factor's attribute. The weight is maximum score of factor. These scores of factor are used to optimal pedestrian path finding as path finding cost with distance, accessibility.

• Journal of The Institute of Information and Telecommunication Facilities Engineering
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• v.2 no.3
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• pp.17-23
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• 2003

Turbo decoding in combination with detection strategy for Multi Access Interference (MAI) cancellation has been shown to be very effective for MC-CDMA system in Rayleigh multi-path fading environment. This paper reports new simulation results on the efficacy of joint decoding and detection for MC-CDMA in nonlinear and fading channel.

• Journal of Institute of Control, Robotics and Systems
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• v.18 no.12
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• pp.1122-1131
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• 2012

This paper presents obstacle avoidance method for scout robot or industrial robot in unknown environment by using IR sensor and vision system. In the proposed method, robots share the information where the obstacles are located in real-time, thus the robots can choose the best path for obstacle avoidance. Using IR sensor and vision system, multiple robots efficiently evade the obstacles by the proposed cooperation method. No landmark is used at wall or floor in experiment environment. The obstacles don't have specific color or shape. To get the information of the obstacle, vision system extracts the obstacle coordinate by using an image labeling method. The information obtained by IR sensor is about the obstacle range and the locomotion direction to decide the optimal path for avoiding obstacle. The experiment was conducted in $7m{\times}7m$ indoor environment with two-wheeled mobile robots. It is shown that multiple robots efficiently move along the optimal path in cooperation with each other in the space where obstacles are located.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.10C
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• pp.956-963
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• 2006

This research studies multi participant consistency and dynamic data shared through 3D scenes in virtual network environments. In a distributed virtual environment of client-server structure, consistency is maintained by the static information exchange; as jerks occur by packet delay when updating messages of dynamic data exchanges are broadcasted frequence, the network bottleneck is reduced by predicting the movement path by using the Dead-reckoning algorithm. In Dynamic data path prediction, the tests the location prediction error between Dead-reckoning convergence interval and error of prediction and actual condition one time above threshold it interpolates a previously location. The shared dynamic data of the 3D virtual environment is implementation using the VRML EAI.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.21 no.11
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• pp.2923-2931
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• 1996

In this paper, the symbol error probability for orthogonal frequency division multiplexing (OFDM) in the multipath fading environment is obtained analytically. In the analysis, OFDM signals with and without the guard interval are considered, and the two-ray fading model is used for the multi-path fading channel. From the analysis results, it is found that the adjacent subchannel interfernce increases the symbol error rate when the guard interval is not employed or shorter than the length of the delay. It is also shown that the adjacent subchannel interference is a Gaussian random variable and its variance depends on the subchannel location and the number of subchannels. Finally, it is found that the variance of the subchannel interference also increases as the power of the signal increases for the OFDM with insufficient guard interval, yieldin an irreducible error at high signal to noise ratio.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.1B
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• pp.108-113
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• 2002

Short range communications between road-side equipments and on-board equipment is very important for ITS(intelligent Transport System). Roadside communication is for short range communication, and needs performance of high data bit rate and should support the function for very short term communication. In addition to it, a radio propagation characteristics is very different according to a road environment. In this paper, for reliable roadside communication, the radio multi-path propagation profile at roadside is measured and the characteristics is analyzed.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.31A no.4
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• pp.47-55
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• 1994

This paper presents the CDMA system using the RAKE receiver over a multipath fading channel and in multi-user environments. The interference between the propagation paths in a multipath fading causes a serious degradation in the mobile communication environment. In order to derive the path inteference and reduce the fading effect, the RAKE receiver is used. In a computer simulation, the path number of a fading channel and the branch number of the RAKE receiver are modified. As a result, the CDMA system using the RAKE receiver gives a better performance than the conventional CDMA system over a multipath fading channel and in multi-user environments.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2003.11a
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• pp.594-598
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• 2003

In this paper, we analyze the performance of UWB(Ultra-WideBand) communication system employing Bi-phase modulation and RAKE Receiver under the MAI(Multiple Access Interference) and the OSI(Other System Interference) environment. Using the multi-path channel model recommended by IEEE P802.15.TG3a, the performance degradation Is described with the number of users, the number of RAKE fingers and training sequences. To meet BER 10e-4 for 20 users at the same time, the number of RAKE fingers are proposed from 3 to 32. And the number of training sequences are limited less than 8 to keep the channel estimation error within 3dB

• Journal of Auto-vehicle Safety Association
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• v.11 no.3
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• pp.30-36
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• 2019

This paper suggests a car-following algorithm for urban environment, with multiple target candidates. Until now, advanced driver assistant systems (ADASs) and self-driving technologies have been researched to cope with diverse possible scenarios. Among them, car-following driving has been formed the groundwork of autonomous vehicle for its integrity and flexibility to other modes such as smart cruise system (SCC) and platooning. Although the field has a rich history, most researches has been focused on the shape of target trajectory, such as the order of interpolated polynomial, in simple single-lane situation. However, to introduce the car-following mode in urban environment, realistic situation should be reflected: multi-lane road, target's unstable driving tendency, obstacles. Therefore, the suggested car-following system includes both in-lane preceding vehicle and other factors such as side-lane targets. The algorithm is comprised of three parts: path candidate generation and optimal trajectory selection. In the first part, initial guesses of desired paths are calculated as polynomial function connecting host vehicle's state and vicinal vehicle's predicted future states. In the second part, final target trajectory is selected using quadratic cost function reflecting safeness, control input efficiency, and initial objective such as velocity. Finally, adjusted path and control input are calculated using model predictive control (MPC). The suggested algorithm's performance is verified using off-line simulation using Matlab; the results shows reasonable car-following motion planning.