• Journal of KIISE:Computer Systems and Theory
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• v.26 no.2
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• pp.211-222
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• 1999

본 논문은 위성간 링크를 이용하여 저궤도 위성망을 구성할 때 발생하는 링크할당 문제를 효율적으로 풀기 위한 기법을 제안한다. 제안된 기법은 먼저 위성 궤도운동의 주기성에 기반하여 저궤도 위성망을 유한상태기계로 모델링한 후에, 유한상태기계의 각 상태에서 최적의 링크할당을 구하기 위해서 조합형 최적화 문제에 많이 쓰이는 시뮬레이팅드 어닐리을 이용한다. 제안된 기법의 이점은 저궤도 위성망을 유한상태기계로 모델링함으로써 도적인 움직임을 보이는 저궤도 위성망에서의 링크할당 문제를 고정된 위상을 가지는 망에서의 링크할당 문제로 단순화시키고 이를 토대로 최적화기법을 적용할 수 있다는 것이다. 시뮬레이티드 어닐링에 의하여 최적화된 링크할당의 성능은 정규링크할당과의 비교.분석을 통해서 평가된다. 최적화된 링크할당과 정규링크할당의 성능분석을 위하여 정적경로배정과 동적경로배정 기법이 고려된다. 시뮬레이션을 통한 실험결과는 정적경로배정을 적용한 최적링크할당 기법이 호 봉쇄확률 측면에서 최고의 성능을 가짐을 보여준다. 링크할당기법이 같은 경우에는 정적경로배정이 동적경로배정보다 우수한 성능을 보이는데 이는 동적경로배정의 경우에 상태전이 후에 경로배정 표가 안정화되기 위해서 많은 시간을 필요로 하기 때문이다. 본 논문에서는 제안된 링크할당 기법은 작은 용량의 위성간 링크를 가지고서 많은 호에대한 서비스를 제공하고자 할 때 유용하며, 호의 서비스를 위하여 실제로 필요한 위성간 링크의 용량은 실험결과로부터 유추될 수 있다.

• Journal of KIISE:Computer Systems and Theory
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• v.26 no.8
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• pp.930-938
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• 1999

미래의 통합 이동 통신망은 멀티미디어 데이터 서비스를 하기 위해 작은 셀로 망이 구성될 것이다. 셀이 작은 경우, 이동 호스트의 셀간 이동이 상대적으로 증가해서 잦은 핸드오프 처리로 서비스 중단이 빈번히 발생할 수 있을 뿐만 아니라 자원의 낭비도 많아지게 된다. 따라서 이런 문제를 해결하기 위해 이동 호스트의 이동성을 예측해서 멀티캐스트 연결을 구성해서 사전 핸드오프 처리를 하는 SGMH방법을 제안한다. SGMH방법의 성능 평가를 위해 핸드오프 처리과정의 데이터 및 제어 정보의 흐름을 분석하고, 망 종속 인자들을 도입해서 버퍼 오버헤드와 서비스 중단 시간 면에서 기존 핸드오프 방법들과 비교했다. 비교 분석한 결과는 제안한 방법이 기존의 방법보다 기지국에서의 버퍼 오버헤드뿐만 아니라 서비스 중단 시간을 줄일 수 있음을 보였다.Abstract For mobile multimedia data services, future mobile communication networks will consist of small cells. In case of smaller cell size, the number of user movements between cells will increase and more network resources will be consumed for processing frequent handoffs. This processing delay will cause frequent connection service disruptions. To solve these problems, a multicast-based handoff method ,called SGMH(Sub-Group Multicast-based Handoff), is suggested. SGMH method estimates future movements of mobile hosts and setups a dynamic multicast connection tree for procesing handoffs. For performance evaluation, we represent flows of data and control messages as timing diagrams and introduce several network related factors. In terms of buffer overhead and service disruption time we compared the SGMH method to other methods. The results show that SGMH method has better performance in that it can reduce consumption of network resources and minimize service disruption time.

• Journal of KIISE:Computer Systems and Theory
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• v.27 no.3
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• pp.277-286
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• 2000

Switch-based network is suitable for the environment of demanding high performance network. Traditional shared-medium Local Area Networks(LANs) do not provide sufficient throughput and latency. Specially, communication performance is more important with multimedia application. In these environments, switch-based network results in high performance. A kind of switch-based network provides higher bandwidth and low latency. Thus high-speed switch is essential to build switch-based LANs. An effective switch design is the most important factor of the switch-based network performance, and is required for the multicast message processing. In the previous cut-through switching technique, switch element reconfiguration has the capability of multicasting and deadlock-free. However, it has problems of low throughput as well as large scale of switch. Therfore, effective multicating can be implemented by using divided hardware unicast and multicast. The objective of this thesis is to suggest switch configuration with these features.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.24 no.4
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• pp.50-56
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• 2010

Supervisory Control and Data Acquisition Systems (SCADAs) is real-time monitor and control systems. SCADA systems are used to monitor or control chemical and transportation processes, in municipal water supply systems, electric power generation, transmission and distribution, gas and oil pipelines, and other distributed processes. SCADA refers to a large-scale distributed system. The supervisory control system is placed on top of a real time control system to control external processes. Emerging security technologies and security devices are decreasing the vulnerability of the power system against cyber threats. Dealing with these threats and analyzing vulnerabilities is an important task for equipment such as RTU, IED and FEP. To reduce such risks, we develop such a SCADA testbed. This paper presents the development of a testbed designed to assess the vulnerabilities SCADA networks(including serial communication).

• Journal of Information Technology and Architecture
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• v.11 no.1
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• pp.99-111
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• 2014

Today, through developing country's Official Development Assistance (ODA) project, Republic of Korea is giving help in establishing communication networks, furnishing PCs and etc, as a help of information base expansion. And to resolve digital divide between countries, Republic of Korea's IT service group dispatch business has also significantly contributed to enhance information application level of developing countries. The conclusion and suggestion of this study is as follow. It is obvious that utilization of information can be affected by capability improvement of developing country's informatization level. However, developing informatization strategy level and environment in long term wise will cause greater influence than to raise immediate informatization base level. Overall, settlement of long term digital divide seems possible when we elevate developing countries' informatization strategy level and environment.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.9 no.2
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• pp.322-329
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• 2005

This paper describes a computer vision system based on active IR illumination for real-time gaze discrimination system. Unlike most of the existing gaze discrimination techniques, which often require assuming a static head to work well and require a cumbersome calibration process for each person, our gaze discrimination system can perform robust and accurate gaze estimation without calibration and under rather significant head movement. This is made possible by a new gaze calibration procedure that identifies the mapping from pupil parameters to screen coordinates using generalized regression neural networks (GRNNS). With GRNNS, the mapping does not have to be an analytical function and head movement is explicitly accounted for by the gaze mapping function. furthermore, the mapping function can generalize to other individuals not used in the training. To further improve the gaze estimation accuracy, we employ a reclassification scheme that deals with the classes that tend to be misclassified. This leads to a 10$\%$ improvement in classification error. The angular gaze accuracy is about $5^{circ}$horizontally and $8^{circ}$vertically. The effectiveness of our gaze tracker is demonstrated by experiments that involve gaze-contingent interactive graphic display.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.9 no.2
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• pp.242-246
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• 2005

RFID(Radio Frequency Identification) which is emerging from a change in digital convergence paradigm and recently rapidly advancing throughout the overall society is the core technology based on Ubiquitous network. In other words, This is a technology to identify the information of the object and recognize the situation by attaching electrical tag to an object and using Reader that can read the information of the object. With the emergence of the technology, it has turned the existing maintenance of the product into the network and intelligence of the product control by using the bar cord to maintain the product and will lead a revolution throughout overall society by affecting the fields of distribution and product maintenance as well as those of medicines, chemicals and food which the electrical tag can be attached to. his paper shows that utilizing the Bluetooth which is a local wireless telecommunication in the standalone imbedded system can implement the piconet configuration among the Readers and the data telecommunication with the main server.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.5 no.7
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• pp.1238-1244
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• 2001

Earlier efforts on optical access concentrated on the design of PONs for the collection and distribution portion of the access network. In these networks the optical hardware in the RN is very simple, but a multiple access protocol is needed for upstream traffic control. On the other hand, the role of communications is already well established in the office environment. With the advent of cheap, affordable broadband communications and the increasing complexity of consumer electronics, it seems natural to extend the network into the home. As the application of Home Area Network is ever increasing, we therefore consider connectivity between access network and home network which generates various traffic to design MAC protocol over residential network. Global-FIFO is quite simple and allows dynamic upstream bandwidth assignment on the basis of a request-and-permit mechanism. It has good bandwidth efficiency and being cell-based, it does not consider the various traffic from home network. In this paper, we design and analyze the new MAC resource assignment algorithm called MQ-FIFO (Multiple Queue-FIFO) that provides good performance under the environment of ATM-PON and Home Network.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2000.10a
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• pp.216-219
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• 2000

Recently, with the advent of satellite communication technologies, network access services through satellites have emerged as an alternaive to existing access network services. Of satellite access services including multimedia services, the high speed internet access service will be one of the important services. Particularly, the efficient transportation of real time internet traffic seems very essential. The aim of this research is to examine the applicability of the IETF RTP protocol in the satellite access network. The RTP has been developed for the QoS-met tranportation protocol of real time traffic over the existing best-effort internet. This paper summmarizes the RW protocol, and desciribes the architecture and the data structure of the implementation of the RTP.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.9 no.7
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• pp.1588-1593
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• 2005

In coagulant control of water treatment plants, rule extraction, one of datamining categories, was performed for coagulant control of a water treatment plant. Clustering methods were applied to extract control rules from data. These control rules can be used for fully automation of water treatment plants instead of operator's knowledge for plant control. To perform fuzzy clustering, there are some coefficients to be determined and these kinds of studies have been performed over decades such as clustering indices. In this study, statistical indices were taken to calculate the number of clusters. Simultaneously, seed points were found out based on hierarchical clustering. These statistical approaches give information about features of clusters, so it can reduce computing cost and increase accuracy of clustering. The proposed algorithm can play an important role in datamining and knowledge discovery.