• 한국ITS학회 논문지
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• 제8권5호
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• pp.114-120
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• 2009

In outdoor visible light communication channels and LED road illumination communications for the intelligent transport systems (ITS), inter symbol interference (ISI) due to multipath propagation prevents high data rate transmission. Indoor wireless optical communication systems utilizing white LED lights and on the road illumination have been studying about it. Generally, plural lights are installed in room and considered to the traffic information system using existing LED traffic lights. Therefore, their optical path difference must be considered. In this paper, the influence of an optical path difference has been investigated and two approaches against this problem are introduced. One uses on-off keying, return-to-zero (OOK-RZ) coding and the other uses optical orthogonal frequency division multiplexing(OFDM).

• 한국인터넷방송통신학회논문지
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• 제16권5호
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• pp.33-38
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• 2016

현재 안드로이드는 유저 레벨의 데몬들을 통하여 시스템에 필요한 기능을 서비스 함수로 지원하고 IPC를 사용해 호출되도록 한다. 그런데 서비스 함수를 관리하는 작업이 빈번하게 사용되는 Critical Path 임에도 불구하고, 유저 레벨 프로세스가 수행하도록 되어 있다. 이러한 분리된 구조는 모듈성과 유연성의 관점에서 효율적이지만 복잡한 소프트웨어 스택 및 컨텍스트 스위치 오버헤드 등으로 서비스 응답 시간이 상당히 저하된다. 본 논문에서는 안드로이드 IPC 매커니즘의 병목점이 되는 부분을 분석하고 개선함으로써 이러한 문제를 해결한다. 우리는 IPC 지연 시간 중 55%가 커널과 컨텍스트 매니저 사이의 커뮤니케이션 오버헤드인 것을 발견하고, 서비스 함수 중 자주 접근되는 것들에 대한 정보는 커널 내에 캐쉬 형태로 유지하는 기법을 제안한다. 제안된 IPC 캐쉬는 안드로이드 5.0에 구현되었으며, 다양한 모바일 벤치마크를 통해 성능평가를 수행한 결과 52.9%의 성능이 향상되었다.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2007년도 춘계종합학술대회
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• pp.829-832
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• 2007

A Mobile Ad Hoc Network is a system of wireless mobiles nodes that dynamically self-organized in arbitrary and temporary network topologies allowing people and devices to inter-network without any preexisting communication infrastructure. Taking into account its nature and challenges and security issues, we present current security solution and analyse the scheme for protecting attacks.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 1999년도 하계종합학술대회 논문집
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• pp.57-60
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• 1999

In many radio communication environments, there is a special component, called inter-symbol interference (ISI), mused by multipath time delay of signal and ISI components impose limitation of the data transmission rate. In this paper, we consider signaling pulse shapes, called partial response signaling (PRS), for minimizing the effect of ISI and show the improvement of performance by applying one of the partial-response signaling (PRS) pulses to two types of receiver system under dependent noise environments through the Monte-Carlo computer simulations.

• 한국위성정보통신학회논문지
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• 제2권2호
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• pp.85-91
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• 2007

The satellite networks provide global coverage. The integration of terrestrial networks with a satellite network is the most attractive approach to develop a global communication system. The IP Multimedia Subsystem (IMS) is intended to be the system that will merge the internet with the telecom world. A user with a dual-mode terminal can access both the satellite network and terrestrial network. The seamless handoff between two networks and a user's QoS level is the major issue concerning this integration. In this paper, we propose IMS-based satellite/terrestrial integrated network architecture for a global communication system. Based on the proposed architecture, an inter-network handoff and end-to-end soft QoS procedure is discussed. Our proposed soft QoS scheme is also analyzed to calculate the number of rejected calls.

• Journal of electromagnetic engineering and science
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• 제6권3호
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• pp.176-181
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• 2006

Signal distortion due to the path loss, shadow, and multi-path fading is very serious in radio channel. In this paper, we propose CDMA-OFDM cooperative communication system based on DFP(Decode and Forward Protocol) to overcome these phenomena using spread spectrum technique, orthogonal sub-carrier, and the space diversity. We simulated proposed system under Rayleigh flat fading channel environment. A variety of simulation results reveal the cooperation can provide performance gain of up to 12 dB over direct communications in ideal inter-user case at BER of $10^{-3}$. And we can also confirm variation of diversity effect as channel environment changes.

• 한국지능정보시스템학회:학술대회논문집
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• 한국지능정보시스템학회 2006년도 춘계학술대회
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• pp.303-310
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• 2006

The sorting algorithms have been developed to take advantage of distributed computers. But the speedup of parallel sorting algorithms decrease rapidly with increased number of processors due to parallel processing overhead such as context switching time and inter-processor communication cost. In this paper, we propose a parallel sorting method which provides linear speedup of an optimal serial algorithm for a system with a large number of processors. This algorithm may even provide superlinear speedup for a practical system. The algorithm takes advantage of an interconnection network properties and its protocol.

• 기술사
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• 제23권1호
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• pp.49-63
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• 1990

A signalling system generally designates electrical conditions and transmissionㆍreceiving programs of exchange control use signals concerning the establishmentㆍreleaseㆍtariff etc of calls between telephone subscribers and an exchange office or inter-exchange offices. In signalling system, different systems are being used according as communication service for control. With the development of exchange and transmission technique and higher functional advance, there exist many kinds of signalling systems. As for the signalling system used in international communication, an international standardization is specially important for the exchange of each country to operate properly and execute a smooth exchange connection. A term "signalling system" is chiefly used in telephone exchange system, while in telex exchange system "signalling condition, " and in data exchange system "protocol" is used. "protocol" is used.; is used.

• 한국경영과학회지
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• 제15권1호
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• pp.47-61
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• 1990

The purpose of this study is to construct a new model named Communication Consensus Value Weighted (CCVW) model based on inter-personal technical communication within a project team, and to design Feasibility Estimates Integrated Terminal System (FEITS) which is a subsystem of R & D Project Planning System/System Alternatives Feasibility Estimation System (RDPPL/SAFES) using the model as a key function for feasibility estimation in that system. This new model aims to integrate technical feasibility estimated by several estimators in the lowest level as the project work breakdown structure which is the indentical conception of a terminal system in RDPPL. The process to obtain the feasibility estimate integrated is presented in this paper.

• 한국항해항만학회지
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• 제34권10호
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• pp.769-774
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• 2010

수중 통신 시스템의 성능은 수중채널의 특성에 영향을 받으며, 잔향 및 다중경로(Multi-path)로 인한 지연확산은 데이터 전송 시인접 심벌간의 간섭(Inter Symbol Interference : ISI)의 원인이 되며, 이는 통신 성능 저하의 주 원인이 된다. 본 논문에서는 잔향 및 다중경로로 인한 인접 심벌간의 간섭을 극복하기위해 OFDM(Orthogonal Frequency Division Multiplexing) 변조기법을 이용한 수중에서의 음향통신 실험을 통해 그 성능을 분석하였다. 그 결과 전송속도가 2 kbps인 경우 BER(Bit Error Rate)이 $1.22{\times}10^{-1}$이였으며, 전송속도가 4 kbps인 경우 BER은 $2.47{\times}10^{-2}$이었다.