• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.2
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• pp.670-683
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• 2016

Network coding, as a new technique to improve the throughput, is studied combined with multi-relay model in this paper to address the challenges of long distance and power limit in deep space communication. First, an amplify-and-forward relaying approach based on analog network coding (AFNC) is proposed in multi-relay network to improve the capacity for deep space communication system, where multiple relays are introduced to overcome the long distance link loss. The design of amplification coefficients is mathematically formulated as the optimization problem of maximizing SNR under sum-power constraint over relays. Then for a dual-hop relay network with a single source, the optimal amplification coefficients are derived when the multiple relays introduce non-coherent noise. Through theoretic analysis and simulation, it is shown that our approach can achieve the maximum transmission rate and perform better over single link transmission for deep space communication.

• Journal of Satellite, Information and Communications
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• v.1 no.1
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• pp.40-47
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• 2006

The next-generation mobile communication system are required to provide high-data-rate and high quality transmission over hostile radio channels. Orthogonal Frequency Division Multiplexing(OFDM) technique regarded as a most promising solution in mobile environment. This paper considers the issue of efficient subcarrier allocation for OFDM system in multi-service application. Proposed algorithm can consider channel gain of each service and divide subchannel. Proposed method considers priority of service and divide more subchannels in high priority service. When proposed algorithm compares with existent algorithm, the convergence rate improves and the calculation amount is decreased.

• Journal of Satellite, Information and Communications
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• v.7 no.2
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• pp.18-24
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• 2012

High current behaviors of the extended drain n-type metal-oxide-semiconductor field effects transistor (EDNMOSFET) for electrostatic discharge (ESD) protection of high voltage operating LDI (LCD Driver IC) chip are analyzed. Both the transmission line pulse (TLP) data and the thermal incorporated 2-dimensional simulation analysis demonstrate a characteristic double snapback phenomenon after triggering of biploar junction transistor (BJT) operation. Also, background doping concentration (BDC) is proven to be a critical factor to affect the high current behavior of the EDNMOS devices. The EDNMOS device with low BDC suffers from strong snapback in the high current region, which results in poor ESD protection performance and high latchup risk. However, the strong snapback can be avoided in the EDNMOS device with high BDC. This implies that both the good ESD protection performance and the latchup immunity can be realized in terms of the EDNMOS by properly controlling its BDC.

• Journal of Satellite, Information and Communications
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• v.9 no.2
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• pp.63-68
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• 2014

This paper proposed a novel compressed sensing (CS) technique for an efficient video transmission of multi-copter. The proposed scheme is focused on reduction of the amount of data based on CS technology. First, we describe basic principle of Spectrum sensing. And then we compare AMP(Approximate Message Passing) with CoSaMP(Compressive Sampling Matched Pursuit) through mathematical analysis and simulation results. They are evaluated in terms of calculation time and complexity, then the promising algorithm is suggestd for multicopter operation. The result of experiment in this paper shows that AMP algorithm is more efficient than CoSaMP algorithm when it comes to calculation time and image error probability.

• Journal of Satellite, Information and Communications
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• v.9 no.4
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• pp.104-110
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• 2014

This paper considers two reconstruction schemes of structured-sparse signals, turbo inference and Markov chain Monte Carlo (MCMC) inference, in compressed sensing(CS) technique that is recently getting an important issue for an efficient video wireless transmission system using multi-copter as an unmanned aerial vehicle. Proposed reconstruction algorithms are setting importance on reduction of image data sizes, fast reconstruction speed and errorless reconstruction. As a result of experimentation with twenty kinds of images, we can find turbo reconstruction algorithm based on loopy belief propagation(BP) has more excellent performances than MCMC algorithm based on Gibbs sampling as aspects of average reconstruction computation time, normalized mean squared error(NMSE) values.

• Journal of Satellite, Information and Communications
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• v.9 no.4
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• pp.82-86
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• 2014

In this paper, we propose a novel modulation scheme specialized in real time broadcast system using a multicopter. Since multicopters have many advantages in aerial photography, they have been widely used in broadcasting technologies. However, because of restrictions on flight time, it is difficult to utilize multicopters in real time broadcasting systems. Therefore, video transmission using multicopter is necessary for low power communication techniques in air channel environment. Performance results of the hybrid modulation in this paper are compared to that of conventional modulations with Bit Error Rate (BER) and Signal to Noise Ratio (SNR) simulations. The results also showed that proposed system is suitable for aerial photography. Experiments demonstrated the superiority of the proposed modulation scheme by showing received symbols through an USRP equipment.

• Journal of Satellite, Information and Communications
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• v.8 no.2
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• pp.36-43
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• 2013

In this study, the high current behaviors and double snapback mechanism of gate grounded_extended drain n-type MOSFET(GG_EDNMOS) device were analyzed in order to realize the robust electrostatic discharge(ESD) protection performances of high voltage operating display driver IC(DDIC) chips. Both the transmission line pulse(TLP) data and the thermal incorporated 2-dimensional simulation analysis as a function of ion implant conditions demonstrate a characteristic double snapback phenomenon after triggering of bipolar junction transistor(BJT) operation. Also, the background carrier density is proven to be a critical factor to affect the high current behavior of the GG_EDNMOS devices.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.61 no.10
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• pp.1387-1392
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• 2012

These days people use a lot of electric power, because industry advancement and a standard of living is elevated. So voltage stability analysis and control problems are very important in these days. U.S.A has already developed voltage stability analysis program, and use it on power transmission scheme such as generator overhaul, transmission line off and so on. So voltage stability analysis is more and more interested in Korea, too. In this paper, we introduce a standard theory of voltage stability analysis and real time voltage stability analysis program that use sPMU(Satellite Phasor Measurement Unit). And we also introduce the calculation result about voltage stability in Jeju power transmission system.

• Bulletin of the Korean Space Science Society
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• 2003.10a
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• pp.35-35
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• 2003

In satellite communication, attenuation, scattering, and depolarization of relatively high frequency waves such as millimeter waves are strongly influenced by rain. In order to study the rain attenuation, we introduce a new theoretical method, which enables us to obtain the reflection and transmission coefficients in arbitrary medium. We adopt this method to examine how the electromagnetic radiation is affected by homogeneous spherical raindrops. It is assumed that the raindrop shape is spherical and linearly locate in one direction. For the radiation of wave in raindrops, we consider the effective permittivity, in which the raindrop is assumed to be spherical. By adopting the invariant imbedding approach, the 1st order differential equations are derived for the reflection and transmission coefficients. We investigate the transmission and reflection of waves for various incident angles when the spherical raindrops are assumed to have random sizes.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2006.11a
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• pp.201-204
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• 2006

이 연구는 DVB-S2 전송시스템을 Ku/Ka대역 위성방송서비스에 적용하는 방안을 제안하였다. 이를 위하여 DVB-S2 전송시스템의 수신성능을 변조방식 및 LDPC 부호 율에 따라 S/W 모의실험을 통하여 분석하였으며, 우리나라가 속한 K지역에서 시간 율에 따른 강우감쇠 정도를 Ku 및 Ka대역에서 분석하였다. 수신성능 분석결과와 시간 율에 따른 강우감쇠 정도를 이용하여, Ku 및 Ka대역에서 특정 시간 율을 만족하는 위성방송서비스를 제공하기 위한 DVB-S2 전송시스템의 변조방식 및 LDPC 부호 율을 제안하였다.