• IEIE Transactions on Smart Processing and Computing
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• 제3권4호
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• pp.212-220
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• 2014

The current cellular communications are optimized for low mobility users, meaning that their performance is degraded at high speed. Therefore, passengers in a high-speed train experience very poor radio link quality due to the significantly large number of simultaneous handovers. In addition, wireless data traffic is expanding exponentially in trains, subways and buses due to the widespread use of smartphones and mobile devices. To solve the inherent problem of cellular communication networks and meet the growing traffic demand, this paper proposes the mobile hotspot network of a millimeter-wave communication system as a mobile wireless backhaul. This paper describes the physical layer design of uplink and downlink in the proposed system, and the performances of uplink and downlink are evaluated under Rician fading channel conditions. The implemented baseband prototype of the proposed millimeter-wave communication modem is presented. This system can provide a Gbps data rate service in high-speed trains carrying hundreds of wireless Internet users.

• 대한전자공학회논문지TC
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• 제47권6호
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• pp.35-41
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• 2010

u-TSN (ubiquitous-transportation sensor network) 시스템은 차량에서의 주기적인 정보를 노변장치가 수집하고 수집된 정보의 분석, 가공하여 교통정보를 제공하는 차세대교통시스템이다. 본 논문에서는 u-TSN 시스템에서의 교통정보 수집을 위한 차량에서의 메시지 전송방안을 제안한다. 기존의 시스템은 0.1초마다 차량 정보를 전송하는 것으로 되어 있다. 본 논문에서는 차량 속도에 따라 차량위치 정보의 전송 주기를 조절하는 알고리듬을 제안한다. 제안 전송방법의 우수성을 컴퓨터 모의실험을 통해 기존 방식과 비교 한다.

• Journal of Power Electronics
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• 제14권5호
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• pp.1008-1027
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• 2014

An electric scooter with a V-belt continuously variable transmission (CVT) driven by a permanent magnet synchronous motor (PMSM) has a lot of nonlinear and time-varying characteristics, and accurate dynamic models are difficult to establish for linear controller designs. A PMSM servo-drive electric scooter controlled by a novel hybrid modified recurrent Legendre neural network (NN) control system is proposed to solve difficulties of linear controllers under the occurrence of nonlinear load disturbances and parameters variations. Firstly, the system structure of a V-belt CVT driven electric scooter using a PMSM servo drive is established. Secondly, the novel hybrid modified recurrent Legendre NN control system, which consists of an inspector control, a modified recurrent Legendre NN control with an adaptation law, and a recouped control with an estimation law, is proposed to improve its performance. Moreover, the on-line parameter tuning method of the modified recurrent Legendre NN is derived according to the Lyapunov stability theorem and the gradient descent method. Furthermore, two optimal learning rates for the modified recurrent Legendre NN are derived to speed up the parameter convergence. Finally, comparative studies are carried out to show the effectiveness of the proposed control scheme through experimental results.

• 한국정보과학회논문지:컴퓨팅의 실제 및 레터
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• 제15권10호
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• pp.766-770
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• 2009

인터넷 망은 대역폭이 일정치 않기 때문에 대용량 콘텐츠의 전송 QoS를 보장하기 어렵다. 현재 QoS를 보장하기 위해 사용되는 보편적인 방법은 콘텐츠 전송 네트워크인 CDN(Content Delivery Network)을 사용하는 방법이다. 본 논문에서는 기존 CDN에 적용할 수 있는 메타데이터를 이용한 콘텐츠 배포 및 관리(CDM: Content Distribution and Management using Metadata) 시스템을 제안한다. CDM 시스템은 전송률을 높이기 위하여 파일 단위로 전송되는 기존 방법 대신 병렬 전송이 가능한 세그먼트 단위 전송 방법을 지원한다. 또한, 사용자가 요구하는 내용의 콘텐츠를 우선 배포하기 위한 내용 기반 검색을 통한 배포방법을 지원한다.

• 한국통신학회논문지
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• 제32권7A호
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• pp.678-685
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• 2007

광전송플랫폼 또는 차세대 패킷, TDM 데이터 통합 스위칭 시스템을 위한 망동기장치를 구현하고, 원더잡음 성분이 NG-SDH 광전송망에 미치는 영향을 제시하였다.

• ETRI Journal
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• 제30권2호
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• pp.282-289
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• 2008

We propose a new mini-slot transmission scheme for a passive optical network (PON) in which each customer can be switched either to access mode or to internetworking mode dynamically. In this paper, we present the system implementation (called LAN-PON) as well as the performance of the proposed transmission scheme to illustrate its feasibility and benefits. A mini-slot scheme can rapidly reduce the queuing delay, which increases due to the flooding of the deflected packets in a deflection scheme. We evaluate the impact of mode switching time on the bandwidth gain (throughput) and delay of local area network (LAN) traffic in the LAN-PON with a mini-slot scheme. We also analyze a theoretical delay model of the proposed scheme. The simulation results demonstrate that switching time has an impact on LAN performance, and the average packet delay of the proposed scheme is significantly improved compared to that of the deflection scheme.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2001년도 ICCAS
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• pp.133.3-133
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• 2001

This paper analyses the real-time performance of Ethernet based intranet whether it is applicable to the real-time network. Unpredictability of transmission delay by collision-delay-retransmission mechanism in CAMA/CD(Carrier Sense Multiple Access with Collision Detect) of Ethernet is the major reason making hard to apply to real-time system. Both retransmission mechanism of TCP(Transmission Control Protocol) for reliability and sliding windows algorithm for high utilization make hard to predict transmission delay. Because real-time control network require fast responsibility and bustle of short-periodic messages, global-clock for collision avoidance and UDP(User Datagram Protocol) for high utilization of network are used. The mathematical models for time-delay that can be occured between ...

• 한국철도학회:학술대회논문집
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• 한국철도학회 2003년도 춘계학술대회 논문집
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• pp.468-473
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• 2003

CCTV network has been implemented to transmit the image information of platfo gate and transfer section to local headquarters in the KNR(Korean National Railroa But. communication system for transferring image information around accident field has not been established yet. thus, at present implementation of communication equipment is necessary for dyn of unspecified accident to be transmitted to headquarters. Copper cable communication network is run by KNR, but it is processing installatio optics cable in connection with the implemental plan for high-speed network from n And, the capacity of communication channel will be guaranteed much more than een station and station, station and central headquarters when fiber optics cable is This study analyzes the image equipment of field for transmission and estimated m transmit image information of accident field to headquarters with using communicat ucture. And, the study considers implemental method of communication network for nce image transmission from dozens to hundreds kilometers.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 하계학술대회 논문집 B
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• pp.1300-1302
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• 2003

CCTV network has been implemented to transmit the image information of platform, ticket gate and transfer section to local headquarters in the KNR(Korean National Railroad). But, communication system for transferring image information around accident field or wayside has not been established yet. thus, at present implementation of communication equipment is necessary for dynamic image of unspecified accident to be transmitted to headquarters. Copper cable communication network is run by KNR, but it is processing installation of optical cable in connection with the implemental plan for high-speed network from now on. And, the capacity of communication channel will be guaranteed much more than now between station and station, station and central headquarters when optical cable is completed. This study analyzes the image equipment of field for transmission and estimated matters to transmit image information of accident field to headquarters with using communication infrastructure. And, the study considers implemental method of communication network for long-distance image transmission from dozens to hundreds kilometers.

• 한국정보기술응용학회:학술대회논문집
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• 한국정보기술응용학회 2005년도 6th 2005 International Conference on Computers, Communications and System
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• pp.77-80
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• 2005

Wireless sensor networks(WSN) technology has various applications such as surveillance and information gathering in the uncontrollable area of human. One of major issues in WSN is the research for reducing the energy consumption and reliability of data. A system with forward error correction(FEC) can provide an objective reliability while using less transmission power than a system without FEC. In this paper, we propose to use LDPC codes of various code rate(0.53, 0.81, 0.91) for FEC for WSN. Also, we considered node-to-node interference in addition to AWGN channel. The proposed system has not only high reliable data transmission at low SNR, but also reduced transmission power usage.