• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.7 no.3
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• pp.219-229
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• 1996

Path loss prediction method, one of the most essential parts in measuring the service area in mobile telecommunication, has been developed for many years. But, wave propagation depends on many kinds of environmental factors such as frequency, distance, the heights of transmitting and receiving antenna and the terrain status(buildings in large city, hilly terrain, mountain). These are the main reasons that the propagation models developed in foreign environments can not fit into Korean propagation condition. In this paper, therefore, we performed the measurement in Korean terrain environment in pager frequency band after deviding the terrain characteristics into six types. With this measured data, we derived several curves that follows the long-term wave progagation behavior and developed the wave propagftion prediction model which calculates the field strength at any point in the service area. The proposed model estimates the field strength in two categories, LOS(line-of-sight), or non LOS. We applied this model using the digital terrain data base and compared with the measured data. The result shows that the errors were between 3~9dB, which turned out to be practical.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.18 no.4
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• pp.97-104
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• 2018

In the conventional direction finding, the antenna is installed at a high position on the ground to detect the position of the target with the environment of the LOS(Line of Sight) as much as the signal receiving environment. However, in order to configure such environment, high cost and installation time were required. In this paper, we use TDOA(Time Difference of Arrival) technique to utilize drones in direction finding, so that four drones can be used for directions finding simulation. Simulations based on drone and TDOA direction finding were constructed using additional signal processing Taylor series and Exact Interactive Algorithm. In the simulation, the receiving power is defined by using the 800MHz path-loss model using the GPS information of the ground direction detection, and the position estimation performance is analyzed when the TDOA technique, the Taylor series, and the Exact Interactive Alogrithm are applied.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.43 no.8
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• pp.669-676
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• 2015

In this paper, a guidance law for intercepting maneuvering target with a desired impact angle is proposed. The proposed guidance law is modified from the optimal impact angle control law for a fixed target and given by a biased PN law with the impact angle control term in addition to the conventional PN law. Three different kinds of desired impact angles in the respect of LOS angle, flight path angle, and relative flight path angle to the target are defined. The performance of the proposed guidance law is investigated via numerical simulations for various air-to-air engagement scenarios.

• Journal of Internet Computing and Services
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• v.6 no.5
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• pp.167-175
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• 2005

In the microcell or picocell-based system the frequent movements of mobiles bring about excessive traffics Into the networks. A mobile location estimation mechanism can facilitate both efficient resource allocation and better QoS provisioning through handoff optimization. Existing location estimation schemes consider only LOS model and have poor performance in presence of multi-path and shadowing. In this paper we study multi-criteria decision making which can increase estimation accuracy by considering other multiple decision parameters than the received signal strength.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2003.11a
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• pp.43-46
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• 2003

This paper presents capacity characteristics of the indoor LOS(Line-Of-Sight) propagation channel for MIMO system at 5GHz. The distance between antenna elements, their moving path, and number of transmitting and receiving antennas can be determined by wanted eigen-vlaue, and channel capacity of the MIMO communication channel using only reliable simulation without measurements. The simulation uses 3D Ray tracing and patch scattering model to which electromagnetic material constants are applied. As distance between antenna elements increases, distribution of the eigen-value show a tendency to decrease, but channel capacity increases in LOS environment. However, despite of short distance between antenna elements, large value of channel capacity is obtained in positions which have high AS. When the position of receiver antennas are shifted, channel capacity hardly changed, and as number of antenna elements increases, channel capacity also increases regularly.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.34 no.7
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• pp.45-54
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• 2006

General unmaned airship, in use of aviation photography, needs both airship -controller and camera-controller who work together in harmony. In oder to reduce this manpower and get the good Geographical Information Systems(GIS) data, it is necessary to use a autopilot controller which guides a exact path lines. This paper presents the autopilot control law base on classical PID control. Moreover, this paper shows the result of flight test, the procedure of gain tuning and LOS guidance algorism that is reduce a tracking error.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.4
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• pp.462-469
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• 2011

In this paper, we propose a novel hybrid codebook design method which combines DFT matrix based codebook for Rayleigh fading and LOS codebook for direct path. Link-level performances employing hybrid codebook outperform the ones employing the conventional codebooks when K-factor of Rician distribution is 0.28 to 0.99. Moreover hybrid codebook shows good performances over not only Rayleigh channel but also high K's Rician channels.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.10B
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• pp.1240-1245
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• 2011

In this paper, channel modeling and analysis of wireless visible light communication(VLC) were studied in indoor circumstance. Photons emitted from LED straightly moved and navigated within indoor, after that a part of photons reached on PD via LOS(Line Of Sight) or NLOS(None Line Of Sight). These received signals had characteristics of delay profile and attenuation, which was multiple-path fading. In this paper, computer simulation of VLC channel was executed under the condition that two LEDs were used for transmitter and three PDs were located at different positions of the 20*8*2.3m sized indoor. BER performance simulation was excuted based on the characteristics of each VLC channel.

• Journal of Advanced Navigation Technology
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• v.10 no.4
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• pp.385-393
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• 2006

In this paper, we proposed a location estimation algorithm considering an extension of searching area in 2.45GHz band RTLS and analyzed its performance in terms of an average estimation error distance. The extendable searching area was assumed to be square of $300m{\times}300m$ and 2 dimensions. The arrangement shape of available readers was considered circle, rectangle, and shrinkage rectangle for extendable searching area. Also, we assumed that propagation path was LOS (Line-Of-Sight) environment, and analyzed the estimation error performance as a function of the number of received sub-blink considering an arrangement shape of available readers in searching area. From the results, compared with rectangle shape, circle shape showed the higher estimation accuracy. Also, we confirmed that the proposed location estimation algorithm provided high estimation accuracy in the shrinkage rectangle shape that was suitable for extension of searching area.

• Journal of the Economic Geographical Society of Korea
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• v.18 no.1
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• pp.17-44
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• 2015

This paper aims at elucidating the characteristics of immigration path and residential location, and analyzing the factors influencing housing ownership structure and preference of residential location factors of Korean immigrants in Los Angeles. The main results of this study are as follows. Firstly, immigration paths of Korean Immigrants are divided by spatial assimilation type and network of mainstream society oriented type. Secondly, according to the results of binomial logistic regression analysis, Korean town as a current residential location is selected by low-income class, aged migrants group, housing non-owner group and longer migration period group. Thirdly, migrants tend to retain detached housings in residential area of mainstream society while migration period go beyond 10 years and incomes exceed $60,000. Finally, according to ANOVA tests on the preferences of residential location factors. high-income and home owers groups more prefer location factors such as economics, natural environment, housing interior facilities, network of mainstream society.