• Journal of Computing Science and Engineering
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• v.5 no.1
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• pp.19-31
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• 2011

In this paper, we propose two new routing schemes for double-layered peer-to-peer systems; a shorter-lower mobility routing scheme and a reverse path routing scheme. The shorter-lower mobility routing scheme first chooses shortest routing paths among possible routing paths and selects the path associated with the relay peer who has lower mobility to improve the reliability of the system. The reverse path routing scheme carries out unicasting (instead of multicasting) based on the reverse path information that can be obtained during the initial file search to further reduce network traffic. The experimental results showed that a double-layered peer-topeer system with the proposed hybrid scheme improved the reliability of the system about 1.5% over the hop count scheme and reduced network traffic by about 0.5% compared to the hop count scheme.

• Journal of Information Processing Systems
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• v.14 no.5
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• pp.1272-1285
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• 2018

The paper presents a novel embedded multifunctional media sever (EMMS) for mobile devices to receive various media programs. Being different from other contemporary system research, the paper mainly studies how to design a reception solution for terrestrial digital television (DTV) on mobile devices and how to enable mobile devices can receive DTV program, enjoy video-on-demand (VOD), achieve video surveillance and relay Internet video program via local Wi-Fi simultaneously. In the system design, we integrate broadcasting-terrestrial DTV tuner, streaming media re-transmission system, VOD disk, video camera and access interface to the Internet into EMMS, which can either receive terrestrial DTV radio signals and demodulate out digital transport stream (TS), or can read streaming media bit-stream from VOD disk, surveillance camera or access interface to the Internet. The experimental results show the proposed system is stable and quality-efficient. Comparing with the other systems, the proposed system has the least packet loss rate and response time.

• Proceedings of the KIEE Conference
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• 1990.07a
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• pp.129-132
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• 1990

This paper reports an expert system for coordination of protective relays in the high voltage transmission system. The proposed system consists of five modules and has adopted the frame and production rule representations achieving the efficient data storage and knowledgebases. It has an interface to the fault program PSS/E and has reduced the data retrival time by implementing the local database containg only the minimum information for the process. Different relay parameters and output formats of the setting results can be easily incorporated owing to the rule-based structure. Graphics-based output helps understanding of the process and enhances the practical power.

• Journal of Communications and Networks
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• v.16 no.2
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• pp.110-120
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• 2014

This article proposes a spectrum sharing method which can avoid the mutual interference in both primary and secondary systems. The two systems make them a priority to use two single-dimension orthogonal signals, the real and imaginary pulse amplitude modulation signals, if the primary system is not in outage with this use. A secondary transmitter is selected to be the primary relay and the active secondary source to perform this. This allows a simultaneous spectrum access without any mutual interference. Otherwise, the primary system attempts to use a full two-dimensional signal, the quadrature amplitude modulation signal. If there is no outage with respect to this use, the secondary spectrum access is not allowed. When both of the previous attempts fail, the secondary system is allowed to freely use the spectrum two whole time slots. The analysis and simulation are provided to analyze the outage performance and they validate the considerable improvement of the proposed method as compared to the conventional one.

• 한국IT서비스학회:학술대회논문집
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• 2003.05a
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• pp.607-614
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• 2003

멀티미디어 스트림 전송에 있어서 대량접속자를 수용하기 위해서는 서버에 많은 리소스와 대역폭이 집중되어야만 하는데, 소수의 클라이언트 접속만을 수용할 수 있고 적은 리소스와 대역폭을 갖는 서버의 경우, 이미 접속한 클라이언트가 서버 기능을 해서 중계할 수 있다면, 추가적인 접속은 중계가 가능한 다른 클라이언트로 접속하게 할 수 있다. 이렇게 피라미드 형태로 접속이 분산하기 위해서 P2P 접속을 이용한다면, 적은 리소스와 대역폭을 가지고도 대량접속자를 수용할 수 있는 대안이 될 수 있다. 실제로 이러한 구조로 어떤 어플리케이션이 가능한지, 또 얼만큼의 성능개선효과가 있는지 고찰해보고자 한다.

• Journal of the Korean Institute of Intelligent Systems
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• v.21 no.5
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• pp.588-594
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• 2011

This paper presents the development of application and management system for guiding job information based on android smart-phone. The real-time informations which are provided from the job portal site, become known by using the smart-phone, and the sever system for saving and managing the related informations has been implemented. Especially, the relay and synchronization protocol of job informations have been designed and the system for managing a transmitting and receiving information is also designed and modelled. The developed application has been made up for and registered in the application store for making good use.

• ETRI Journal
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• v.29 no.1
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• pp.27-35
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• 2007

Energy savings in orthogonal frequency division multiplexing (OFDM) systems is an active research area. In order to achieve a solution, we propose a new cooperative relaying scheme operated on a per subcarrier basis. This scheme improves the bit error rate (BER) performance of the conventional signal-to-noise ratio (SNR)-based selection relaying scheme by substituting SNR with symbol error probability (SEP) to evaluate the received signal quality at the relay more reliably. Since the cooperative relaying provides spatial diversity gain for each subcarrier, thus statistically enhancing the reliability of subcarriers at the destination, the total number of lost subcarriers due to deep fading is reduced. In other words, cooperative relaying can alleviate error symbols in a codeword so that the error correction capability of forward error correction codes can be fully exploited to improve the BER performance (or save transmission energy at a target BER). Monte-Carlo simulations validate the proposed approach.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.10 no.4
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• pp.116-124
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• 2011

For Binary CDMA network, communication can be accomplished only within a Pico-net on the boundary of management by the master station because it manages network resources of each entity. In this research, we try to overcome these limits and extend the application for Binary CDMA system to broad-band network. We suggest a new Binary CDMA router such that network is devised by cell unit and multiple Pico-net and a unique address is assigned to each Pico-cell to relaying data between Pico-cells.

• Proceedings of the KSR Conference
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• 2003.05a
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• pp.493-498
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• 2003

Harmonic current originating from electric locomotives can be magnified due to the impedance characteristics of power supply circuit and bring about various problems. That is, electromagnetic interference with communication lines, operational trouble in signaling, overheat and/or vibration in power capacitor, mis-operation in protection relay and so on. Therefore, the exact assessment of the harmonic current flow must be undertaken at design and planning stage for the electric traction systems. For these reasons, this study propose a new approach to model and to analyse traction power feeding system focused on system response to current and voltage harmonic(PART I ). Measurements of harmonics are also performed for railway power supply systems under normal operation. Spectrum and distortion analyses in measurement data are variously described in PART II

• Proceedings of the KSR Conference
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• 2003.05a
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• pp.499-504
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• 2003

Harmonic current originating from electric locomotives can be magnified due to the impedance characteristics of power supply circuit and bring about various problems. That is, electromagnetic interference with communication lines, operational trouble in signaling, overheat and/or vibration in power capacitor, mis-operation in protection relay and so on. Therefore, the exact assessment of the harmonic current flow must be undertaken at design and planning stage for the electric traction systems. For these reasons, this study propose a new approach to model and to analyse traction power feeding system focused on system response to current and voltage harmonic(PART I ). Measurements of harmonics are also performed for railway power supply systems under normal operation. Spectrum and distortion analyses in measurement data are variously described in PART II