• 전자공학회논문지 IE
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• v.48 no.4
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• pp.61-68
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• 2011

As business management has a high level of dependence on Informational Technology (IT), protecting assets of a company from disaster is one of the most important thing that IT operating managers should consider. Because data or information is a major source of operation of the company, data security is the first priority as an aspect of continuity of business management. Therefore, this paper will realize disaster recovery system, which is suspended because of disaster, based on cloud computing system. Realized High Available Replicate System applied a method of multi thread target database to improve Replicate performance, and real time synchronize technology can improve efficiency of network. From Active to Active operation, it maximizes use of backup system, and it has a effect to disperse load of source database system. Also, High Available Replicate System realized consistency verification mechanism and monitoring technique. For Performance evaluation, High Available Replicate System used multi thread method, which shows more than threefold of replicate performance than single thread method.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.9B
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• pp.581-590
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• 2005

The IEEE 802.17 Resilient Packet Ring Working Group develops standards to support the development and deployment of Resilient Packet Ring networks in Local, Metropolitan, and Wide Area Networks for resilient and efficient transfer of data Packets at rates scalable to many gigabits Per second. It was known that the fairness algorithm of the IEEE 802.17 Resilient Packet Ring suffers from throughput degradation under an unbalanced overload. This Paper proposes a congestion release advertisement method to improve this throughput degradation and discusses its performance. Under the proposed method, a congested node decides whether its congestion is released or not. If released, it advertises the congestion release to upstream nodes, and then upstream nodes transmit their traffic without uy regulation. The proposed method is compatible with the legacy fairness algorithm.

• Journal of the Korean Institute of Telematics and Electronics
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• v.26 no.1
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• pp.129-139
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• 1989

During a signal is being transmitted, an interference signal can be introduced through an unknown channel. In these cases, an adaptive system, so called adaptive noise canceller, can restore the original signal from the corrupted signal by first identifying the unknown interference channel on the minimum mean square error criteron, and then by cancelling the interference signal using the identified interference channel. Whereas this method is quite effective when the a priori knowledges about the characteristics of the interference signal and of the intrference channel are unknown or time-varyng, but has a drawback that the presence of the original signal has a severe effect on the optimum value of the interference channel to be identified on the miniumum mean square eror criterion In this paper an adaptive noise canceller and its algorithms are introduced that can restore the original signal more accurately especially when the correlatedness between the original signal and the interference signal is small.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.17 no.5
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• pp.111-117
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• 2017

The National Competency Standards (NCS) was designed to implement a competence-based society and solve the problem of inconsistency between the industrial field and education, training, and certification system. This study designed and developed the Korean NCS core vocational competence system, in accordance with the NCS, as an infrastructure to solve fundamental problems such as re-education and the social costs that are incurred in the workplace. Further, this study designed and developed standard indicators to evaluate the technical performance of the system for the global advancement of the Korean NCS core vocational competence system. The NCS core vocational competence system has been developed as an appropriate response type for multiple devices such as computers, tablet PCs, and cellular phones. For the global advancement of the Korean NCS core vocational competence system, this study designed and developed 10 performance evaluation indicators in accordance with 10 global standards, such as linkage-target operating system, interface protocol, packet format, encryption, class component, simultaneous access number, supervisor-to-testtaker response speed, server-to-admin response speed, auto-recovery speed for test answers, and real-time answer transmission speed.

• Journal of Internet of Things and Convergence
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• v.6 no.3
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• pp.39-44
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• 2020

In this paper, we propose a SDN-based fog computing service mobility support scheme. Fog computing architecture has been attracted because it enables task offloading services to IoT(Internet of Things) devices which has limited computing and power resources. However, since static as well as mobile IoT devices are candidate service targets for the fog computing service, the efficient task offloading scheme considering the mobility should be required. Especially for the IoT services which need low-latency response, the new connection and task offloading delay with the new fog computing node after handover can occur QoS(Quality of Service) degradation. Therefore, this paper proposes an efficient service mobility support scheme which considers both task migration and flow rule pre-installations. Task migration allows for the service connectivity when the fog computing node needs to be changed. In addition, the flow rule pre-installations into the forwarding nodes along the path after handover enables to reduce the connection delay and service interruption time.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.4B
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• pp.659-669
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• 2010

The P2P IPTV will create a new paradigm for the Internet services. However, it cannot guarantee the reliability of their server and QoS because of using common Internet users(peers) for SIP server or relay server, though the infrastructural cost is low. This paper proposes the ISP-based P2P IPTV architecture which can solute the limitations of conventional P2P-based IPTV. In this model, ISP can build P2P overlay network with ISP servers and directly manage each server needed for session connection. So, the servers have higher performance and better reliability than previous one. Besides, robustness is improved because each sever is set by P2P overlay network. To evaluate the characteristics of the ISP-based P2P IPTV architecture, we simulate it for some parameters which are end-to-end streaming delay time, connection delay time and traffic amount. We compared the proposed architecture with the conventional P2P architecture about video service and confirmed that the performance of ISP-based P2P IPTV is better than conventional P2P based IPTV.

• Proceedings of the Korea Water Resources Association Conference
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• 2007.05a
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• pp.795-799
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• 2007

최근 정보통신산업이 급속도로 발전함에 따라 Internet을 이용하여 각종 정보를 쉽게 얻을 수 있게 되어 수자원 분야에도 정보의 공유와 자료의 통합이 활발히 이루어지고 있다. 또한 재해정보를 효율적이고 직관적으로 표현하기 위해서 방재업무에 GIS를 도입하고 있다. Internet을 통한 손쉬운 정보의 취득은 효율적인 재해관리에 매우 중요하며, 자료의 효율적인 관리와 표현을 위한 GIS기법 또한 필수적이다. 따라서 본 연구에서는 Internet과 GIS를 결합하여 보다 많은 사람들이 신속하고 정확한 재해정보를 얻을 수 있게 하며, 방재 업무에 활용토록 하여 재해에 의한 주민들의 생명의 위협과 재산피해를 줄이도록 하는데 그 목적이 있다. 효과적인 재해관리를 위해서는 계획과 관련된 정보, 재해발생 이력, 대상지역의 각종 정보가 통합되어 실시간으로 전달될 필요가 있다. 또한 이러한 정보들을 빠른시간내에 이해하고 분석하여 대책을 수립하고 시행해야한다. Internet GIS는 비상상황에 대비한 계획과 대처 그리고 복구사업에 있어 가장 정확하고 신속한 정보를 제공해 줄 수 있다. 즉, Internet GIS는 방대한 양의 정보를 효과적이고 지능적으로 분석이 가능하며, 이해하기 쉬운 그래픽 기반의 자료를 보여주므로 방재업무에 큰 도움을 줄 수 있다. Internet GIS를 방재정보 시스템에 이용할 경우 에 있어 장점, 약점, 기회, 위기에 대한 SWOT분석을 실시하였다. Internet이라는 환경의 장점을 그대로 이어받아 비용면에서 효과적이며 적용범위와 사용자층도 넓어지게 된다. 또한 누구나 간편하게 이용할 수 있어 협력체계 또한 쉽게 구축할 수 있으며 빠른 정보의 교환이 가능하다. 하지만, 인터넷에 의존한다는 점에 있어 서버가 자연재해에 노출될 경우 시스템 자체가 제 기능을 할 수 없으며 여러명이 동시에 서버에 접속을 하기 때문에 컴퓨터에 부하가 많이 걸리는 모델링이나 복잡한 분석은 실시하기 어려우며, 대용량 데이터를 전송할 수 있는 대역폭이 확보 되어야 한다. 또한, Internet 환경으로 개발을 해야되기 때문에 데스크탑용 GIS에 비해 개발속도가 느리며 개발 초기비용이 많이 들게 된다. 하지만, 네트워크 기술의 발달과 모바일과의 연계 등으로 이러한 약점을 극복할 수 있을 것으로 판단된다. 따라서 본 논문에서는 인터넷 GIS를 이용하여 홍수재해 정보를 검색, 처리, 분석, 예경보할 수 있는 홍수방재정보 시스템을 구축토록 하였다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.10C
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• pp.1036-1043
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• 2005

In this paper, we propose a sequential motion vector recovery algorithm for H.264 video coding standard. Motion vectors of H.264 video coding standard cover relatively smaller areas than other standard, since motion estimation of H.264 takes place in the fashion of variable block size. Therefore, the correlation of motion vectors between neighboring blocks increases as the block size of motion estimation is lowered. Under the framework of sequential recovery, we introduce a motion vector recovery using $\alpha$-trimed mean filter. Experimental results show that proposed algorithm is useful in real time video delivery .with nearly comparable or better visual quality than previous approaches such as macro block boundary matching and Lagrage interpolation.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.4
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• pp.628-636
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• 2015

In this paper, we propose a non-convex compressed sensing(NCCS)-based channel state information(CSI) feedback scheme for massive multiple-input multiple-output(MIMO) systems. Combining the random vector quantization(RVQ), the proposed scheme permits a transmitter to obtain CSI with acceptable accuracy under substantially reduced feedback load. Furthermore, it recovers CSI from fewer measurements than that of existing convex compressed sensing(CCS)-based schemes even if the measurements are inaccurate and incomplete. Simulation results show that the proposed scheme achieves higher throughput than both existing CCS-based feedback scheme and random vector quantization(RVQ) feedback scheme with the same feedback load.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.22 no.9
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• pp.1957-1967
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• 1997

Adaptive channel equlization accomplished without resorting to a training sequence is known as blind equalization. In this paper, in order to reduce the speed of the convergence and the steady-state mean squared error simultaneously, we propose the multi-stage RD(radius-directed) algorithm derived from the combination of the constant modulus algorithm and the radius-directed algorithm. In the starting stage, multi-stage RD algorithm are identical to the constant modulus algorithm which guarantees the convergence of the equalizer. As the blind identical to the constant modulus algorithm which guarantees the convergence of the equalizer. As the blind equalizer converges, the number of the level of the quantizers is increased gradually, so that the proposed algorithm operate identical to the radius-directed algorithm which leads to the low error power after the covnergence. Therefore, the multi-stage RD algorithm obtains fast convergence rage and low steady stage mean square error.