• Journal of the Institute of Electronics Engineers of Korea TC
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• v.40 no.12
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• pp.145-154
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• 2003

In this paper we propose service schemes for the control message of voice and data connections served by a Softswitch in NGN (next generation networks). After that we propose a method of evaluating the performance of a Softswitch that provides a limited delay to voice connections. Via numerical experiments, we verify the implication of the proposition in the design of a Softswitch, which simultaneously incorporates voice and data services in the NGN framework.

• Proceedings of the KIEE Conference
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• 2005.10b
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• pp.466-468
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• 2005

MMORPG enables thousands of players to play in an evolving virtual world at the same time over the internet. So, the load of this kind of games is heavier than that of any other precedents. One of load balancing methods is map-partition to divide the load of entire system which is vulnerable to delay message between clients and servers. In this paper, we propose a game architecture using MigAgent to help migration of player character between field servers and to reduce message traffic between clients and field servers.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.11a
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• pp.717-720
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• 2000

Event-driven communication protocols such as CAN(Controller Area Network) have inherent packet delays due to the contention process for the use of network medium. These delays are stochastic in nature because most packets arrive at random time instants. The stochastic property of the delay adversely influences the control system's performance in terms of stability, responsiveness and steady-state error. Another problem for safety-critical application such as brake-by-wire systems is the reliability of the communication modules that can fail abruptly. This paper deals with two methods to overcome the above problems : (i) scheduling method that can maintain packet delays under some acceptable level, and (ii) redundancy management of communication modules that prescribes dual-redundancy modules' behavior when one of them fails.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.4
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• pp.1223-1236
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• 2014

With the extension of wireless technology, vehicular ad hoc networks provide important services for the dissemination of general data and emergency warnings. However, since, the vehicle topology frequently changes from a dense to a sparse network depending on the speed of the moving vehicles and the time of day, vehicular ad hoc networks require a protocol that can facilitate the efficient and reliable dissemination of emergency messages in a highly mobile environment under dense or intermittent vehicular connectivity. Therefore, this paper proposes a new vehicular broadcast protocol, called BL-CAST, that can operate effectively in both dense and sparse network scenarios. As a low overhead multi-hop broadcast protocol, BL-CAST does not rely on the periodic exchange of beacons for updating location information. Instead, the location information of a vehicle is included in a broadcast message to identify the last rebroadcasting vehicle in an intermittently connected network. Simulation results show that BL-CAST outperforms the DV-CAST protocol in terms of the end-to-end delay, message delivery ratio and network overhead.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.57 no.1
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• pp.30-35
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• 2008

In this paper, the application of power Quality monitoring based on Sampled Value(SV) which is introduced in the IEC61850 International Standard for substation communication are discussed. Firstly, while Merging Unit(MU) is designed as a process level device transmitting sensor data, the practical problems such as time delay compensation and optical fiber communication are encountered. Secondly, the Sampled Value message which is proper to a power quality monitoring system is presented. Because the power quality monitoring system requests less time-critical service compared to protection and control applications, the Sampled Value service message structure is introduced to improve efficiency. Lastly, the power quality monitoring server having various power quality analysis functions is suggested to verify the performance of Merging Unit With the diverse experiments, it is proved that the process bus distributed solution is flexible and economic for the power quality monitoring.

• International Journal of Railway
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• v.3 no.3
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• pp.106-112
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• 2010

Accidents at level crossing have large portion on train accidents, and causes economical loss by train delay and operational interruption. Various safety equipments are employed to reduce the accident at level crossing, but existing warning device, and crossing barrier are simple train-oriented protection equipments. In this paper, intelligent railway level crossing system is proposed to prevent and reduce accidents. For train driver's prompt action, image of level crossing and obstacle warning message are continuously provided to train driver through wireless communication in level crossing control zone. Obstacle warning messages, which are extracted by computer vision processing of captured image at level crossing, are recognized by train driver through message color, flickering and warning sound. It helps train driver to decide how to take an action. Meanwhile, for vehicle driver's attention, location and speed of approaching train are given to roadside equipments. We identified the effect of proposed system through test installation at Sea train and Airport level crossing of Yeong-dong line.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.56 no.1
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• pp.13-18
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• 2007

In this paper, authors deal with an application of power quality monitoring using the Sampled Value which is described in the IEC61850 International Standard for substation communication. Firstly, while Merging Unit is designed as a process level device transmitting sensor data, the practical problems such as time delay compensation and optical fiber communication are issued. Secondly, the Sampled Value message which is proper to a power quality monitoring system is presented. Because the power quality monitoring system requests non time critical service comparing to protection and control applications, the Sampled Value service message structure is introduced to improve efficiency. At last, the power quality monitoring server having various power quality analysis functions is suggested to verify the performance of Merging Unit. With the diverse experiments, it is proved that the process bus distributed solution is flexible and economic for the power quality monitoring.

• The Transactions of the Korea Information Processing Society
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• v.4 no.11
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• pp.2732-2744
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• 1997

This paper is based on multicasting model in k-ary n-cubes, and Proposes an adaptive wormhole routing algorithm which allows faults and channel contention. The proposed algorithm only requires $2{\times}n$ virtual channels per physical channel which is proportional to the dimension n in order to allow (n-1) faults in a k-ary n-cube. This method uses smaller number of virtual channels than the previously Proposed adaptive routing algorithms [5, 18]. Through a chaos simulator, we have measured message delay considering fault-tolerant as well as message traffic to our adaptive routing algorithm.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.5 no.2
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• pp.440-456
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• 2011

In this paper, we introduce a novel Public Key Infrastructure (PKI) based message authentication scheme that takes advantage of temporal and spatial uniqueness in physical layer channel responses for each transmission pair in vehicular communication networks. The proposed scheme aims at achieving fast authentication and minimizing the packet transmission overhead without compromising the security requirements, in which most messages can be authenticated through an extreme fast physical-layer authentication mechanism. We will demonstrate that the proposed secure authentication scheme can achieve very short message delay and reduced communication overhead through extensive analysis and simulation.

• Proceedings of the Korea Information Processing Society Conference
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• 2012.11a
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• pp.829-832
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• 2012

MQTT(Message Queue Telemetry Transport) 는 IBM 에서 발표한 오픈 프로토콜이다. MQTT 는 메시지 전달의 신뢰성 보장을 위하여 3 단계의 QoS 를 지원한다. 본 논문에서는 실제 유/무선 네트워크 환경에서의 Publish 클라이언트에서 Broker 서버를 지나, Subscribe 클라이언트에 이르기까지 메시지 전달에 대하여 분석한다. 메시지는 MQTT 의 3 단계의 QoS 레벨과 페이로드 크기를 다양하게 전달하여 패킷을 캡쳐하고, 메시지에 대한 종단 간 지연과 메시지 손실에 대한 분석과 상관관계의 결과를 제시한다.