• Proceedings of the Korea Multimedia Society Conference
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• 2004.05a
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• pp.567-570
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• 2004

본 논문은 유비쿼터스 컹퓨팅 환경에서 미디어 서비스를 이용하는 사용자가 위치 이동에 따라 미디어 서비스를 요구할 경우 QoS의 저하 없이 유연하게 미디어를 서비스하기 위한 버퍼 관리 모델을 제안한다. 사용자는 미디어 서비스를 받기 위하여 일반 데스크탑 뿐만 아니라 셋탑박스, PDA와 같은 이동 단말기 등 다양한 형태의 단말환경으로 연결하여 이용 할 수 있다. 이와 같이 사용자에게 미디어 서비스를 제공할 경우 유연한 미디어 스위칭이 필요하다. 본 논문에서 제안하는 미디어 스위칭을 위한 버퍼 관리는 사용자의 이동에 따라 유연하게 서비스를 제공되기 위한 단말의 센서관리 모듈, 실시간으로 미디어를 제공할 수 있는 미디어 스트리밍 서버, 그리고 미디어 서비스의 세션과 버퍼를 관리하기 위한 관리 모듈로 구성된다.

• Proceedings of the Korea Information Processing Society Conference
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• 2001.04a
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• pp.247-250
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• 2001

클러스터링 웹서버에서 트래픽 문제에 대한 장기적인 해결책으로, 서로 다른 종류의 트래픽들에 우선순위를 부여하고, 이에 따라 네트웍에서 트래픽을 지능적으로 조절하기 위하여 QoS 보장을 위한 목표를 설정한다. 구체적으로 CBQ 구현에 관련된 실시간 스케줄링 기법을 이용하고, 패킷크기의 최적화와 접속별 대역폭 공정배분을 통한 트래픽의 효율적인 관리를 할 수 있음을 보인다.

• Journal of KIISE:Information Networking
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• v.30 no.4
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• pp.535-544
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• 2003

Integrated services networks should guarantee end-to-end delay bounds for real-time applications to provide high quality services. A real-time scheduler is installed on all the output ports to provide such guaranteed service. However, scheduling algorithms studied so far have problems with either network utilization or scalability. Here, network utilization indicates how many real-time sessions can be admitted. In this paper, we propose service curve allocation schemes that result in both high network utilization and scalability in a service curve algorithm. In service curve algorithm, an adopted service curve allocation scheme determines both network utilization and scalability. Contrary to the common belief, we have proved that only a part of a service curve is used to compute deadlines, not the entire curve. From this fact, we propose service curve allocation schemes that result in a constant time for computing deadlines. We through a simulation study that our proposed schemes can achieve better network utilizations than Generalized processor Sharing (GPS) algorithms including the multirate algorithm. To our knowledge, the service curve algorithm adopting our schemes can achieve the widest network utilization among existing scheduling algorithms that have the same scalability.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.1B
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• pp.52-63
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• 2004

Packet loss process of cdma2000 mobile Internet channel deployed in Korea is modeled as a two state Markov process known as Gilbert model. This paper proposes the procedures to derive four parameters of the our modified Gilbert model from packet loss trace taken from two major cdma2000 networks in Korea. These four parameters are derived in various situations, that is, with fixed and moving terminals, in open field and urban areas. They can be used to produce synthetic packet loss patterns for study of the channel. Moreover, if they are calculated on-line during multimedia service, they can be used to make loss protection controls adaptive to network condition.

• Journal of the Korea Society of Computer and Information
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• v.9 no.4 s.32
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• pp.157-165
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• 2004

The paper suggests that web-server security management system will be able to detect the web service attack accurately and swiftly which is keeping on increasing at the moment and reduce the possibility of the false positive detection. This system gathers the results of many unit security modules at the real time and enhances the correctness of the detection through the correlation analysis procedure. The unit security module consists of Network based Intrusion Detection System module. File Integrity Check module. System Log Analysis module, and Web Log Analysis and there is the Correlation Analysis module that analyzes the correlations on the spot as a result of each unit security module processing. The suggested system provides the feasible framework of the range extension of correlation analysis and the addition of unit security module, as well as the correctness of the attack detection. In addition, the attack detection system module among the suggested systems has the faster detection time by means of restructuring Snort with multi thread base system. WSM will be improved through shortening the processing time of many unit security modules with heavy traffic.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.9 no.5
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• pp.1002-1011
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• 2005

In this paper. we design and implement a bi-directional broadcasting system, so called return channel server, to allow users to participate in a broadcasting program by using a hi-directional interaction channel. To provide user participation in a program and reflect the user's opinions or responses in real time, the return channel server can be viewed as consisting of four major functional modules: a control module, network interface module, DBMS module, and real-time content authoring module. To construct a return channel server that has a service independent architecture, we designed a return channel server to include the hierarchical structure. The presented return channel server consists of two parts: an RCSAE(return channel server application environment) and RCSA(return channel server application). An RCSA is composed of an execution code and a parameter for executing the execution code. RCSA defines the procedures for providing a specific broadcasting program using the return channel server. On the other hand, an RCSAE provides the environment for the execution of RCSAS. By adopting RCSAE and RCSA, we construct the return channel server that has a service-independent architecture which are shown by the test.

• Journal of the Korea Computer Graphics Society
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• v.2 no.2
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• pp.29-36
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• 1996

This paper presents animation techniques and issues involved in virtual environments where the participants interact with each other through a network. The state of the participant should be collected at each local site, and broadcasted to the other sites. Because information exchange is minimal, animation techniques are applied to convert the incoming low DOF parameters into high DOF joint angles that completely determine the configuration of the agents at each frame. As a case study, a software system VRLOCO is introduced, which has been developed by the author over the last five years.

• Proceedings of the Korea Contents Association Conference
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• 2003.05a
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• pp.198-201
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• 2003

Changes in internet and network environment make it possible to provide high-quality content services in real time. As demand for digital content is increased, problems related to intellectual property rights are getting more important. Streaming service like video-on-demand solved this problem by preventing content from being saved. But, as the advent of several tools able to save streamed content, the streamed content is not free from these problems any more. So, with security countermeasure like access control, new technologies to control and manage rights for content are needed. One of the solutions is DRM In this paper, we describe a DRM-based streaming service that can send the ASF stream which is the multimedia file format of Microsoft.

• Proceedings of the KIEE Conference
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• 2001.07c
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• pp.1844-1846
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• 2001

광섬유는 저손실, 광대역의 전송특성을 가지며 세경(細徑), 경량등 많은 장점을 가지고 있지만 동케이블과 같이 파단점, 불연속점등의 장해점 탐색에 대한 어려움이 있다. 이러한 문제점을 해결하기 위하여 OTDR(Optical Time Domain Reflectometer)은 고감도, 고정도의 광센싱 기술, 극초단 광펄스 레이다 기술, 광다중화 센서 네트웍기술, 실시간 광신호처리 기술 등 정밀 광계측 및 신호처리기술을 적용하여 설치된 광섬유의 손실 정도를 측정하는 시스템으로 광섬유에 입사된 광의 산란 가운데 Rayleigh 산란에 의해서 생기는 후방산란광을 관측하여 광파이버의 파단점 탐색 및 손실측정이 가능하다. 최근 대부분의 유선통신망은 광섬유를 이용한 광통신방식으로 이루어지고 있으며 이러한 광섬유의 고장점을 찾기 위한 방법은 OTDR방식이 유일하다고 할 수 있다. 본 논문은 Rayleigh 후방산란에 의한 광학적 특성을 규명하고 이러한 특성을 이용하여 이용한 광섬유 유지보수용 계측시스템을 설계, 제작하고 실험한 결과에 대하여 설명하고 고찰하였다. 측정거리를 40Km까지 측정하도록 하였으며, 모니터상에서의 거리 분해능은 5m정도를 가지며 1310nm의 파장을 사용하였다.

• Journal of Korean Society of Transportation
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• v.20 no.5
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• pp.145-152
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• 2002

Real-time queueing information and/or predictive queue built-up information can be a good criterion in selecting travel options, such as routes, both for users, and for operators in operating transportation system. Provided properly, it will be a key information for reducing traffic congestion. Also, it helps drivers be able to select optimal roues and operators be able to manage the system effectively as a whole. To produce the predictive queue information, this paper proposes a predictive model for estimating and predicting queue lengths, mainly based on Kalman Filter. It has a structure of having state space model for predicting queue length which is set as observational variable. It has been applied for the Namsan first tunnel and the application results indicate that the model is quite reasonable in its efficacy and can be applicable for various ATIS system architecture. Some limitations and future research agenda have also been discussed.