• 한국멀티미디어학회논문지
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• 제19권2호
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• pp.155-162
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• 2016

Several distributed scheduling policies have been proposed with the objective of attaining the maximum throughput region or a guaranteed fraction throughput region. These policies consider only the theoretical throughput and do not account the lost in throughput due to the time complexity of implementing an algorithm in practice. Therefore, we propose a novel concept called effective throughput to characterize the actual throughput by taking into account the time complexity. Effective throughput can be viewed as the actual transmitted data without including the control message overhead. Numerical results demonstrate that in practical scheduling, time complexity significantly affects throughput. The performance of throughput degrades when the time complexity is high.

• 한국멀티미디어학회논문지
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• 제11권2호
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• pp.129-142
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• 2008

웹 서비스 사이트들의 급속한 증가에 따라 수많은 유사 웹 서비스들 중에서 최적의 서비스를 찾는 방법이 문제가 되고 있다. 매치메이커는 주어진 질의에 적합한 서비스 사이트를 찾아주는 일종의 에이전트 시스템이다. 본 논문에서는 분산 시각 미디어 검색 프레임워크인 HERMES를 위한 매치메이커를 제안하고, QoS를 기반으로 결과 서비스 사이트의 순위를 부여하는 방법을 설명한다. 또한 실험을 통해 제안 방법의 유용성과 정확성을 보인다.

• 한국멀티미디어학회논문지
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• 제7권2호
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• pp.241-250
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• 2004

본 논문에서는 모바일 온라인 컨텐츠를 위한 이질적인 분산환경에서 단말기간 컨텐츠의 전역상태일치를 보장하고, 통신의 흐름을 조절하는 기능을 가진 서버와 단말기간의 응용계층 프로토콜을 제안하였다. 제안된 프로토콜에서는 단말기의 흐름제어를 위한 부담을 줄이고, 컨텐츠의 내용을 서버가 유지 보관할 필요가 없다. 제안된 응용계층의 프로토콜을 이용하여 CP들은 그들의 컨텐츠를 응용 프로세서로 쉽게 개발할 수 있다. 특히 가입자 수의 증가에 따라 서버규모도 쉽게 확장 가능하다.

• 한국멀티미디어학회논문지
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• 제8권12호
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• pp.1638-1648
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• 2005

The SEM approach to PKl offers several advantages, such as immediate revocation of users' signing ability without CRLs and compatibility with the standard RSA. However, it has a weakness against denial of service attack caused by breaking down or being compromised. G. Vanrenen et al. proposed a distributed SEM approach to overcome the weaknesses. However, it does not provide the desirable properties such as instant availability and immunity against denial of service attack, due to inadequate usage of threshold cryptography and proactive secret sharing. In this paper, we point out its structural contradictions and propose a modified version of distributed SEM approach.

• 한국멀티미디어학회논문지
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• 제19권11호
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• pp.1871-1877
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• 2016

In this paper, a Wireless USB (WUSB) protocol is adopted for development of ASMD (Adaptive Source Multi Device) N-screen wireless services. WUSB is the USB technology merged with WiMedia PHY and Distributed-MAC (D-MAC). However, the current WUSB protocol can't provide seamless N-screen streaming services to moving WUSB devices in home network environment. Therefore, to provide the ASMD N-screen services through WUSB based on D-MAC protocol, a channel management scheme is proposed to support seamless mobility between adjacent ASMD groups for wireless IPTV N-screen services. In simulation results, proposed ASMD channel management (ACM) scheme is compared with conventional WUSB channel management scheme in view points of throughput, average path interference and energy consumption according to various numbers of nodes and elapsed simulation times. Through simulation results, it is explained that proposed ASMD channel management (ACM) scheme should be adopted in the WUSB protocol to realize ASMD N-screen wireless services.

• Journal of Multimedia Information System
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• 제7권2호
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• pp.125-136
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• 2020

Nowadays, cloud computing is becoming more popular among companies. However, the characteristics of cloud computing such as a virtualized environment, constantly changing, possible to modify easily and multi-tenancy with a distributed nature, it is difficult to perform attack detection with traditional tools. This work proposes a solution which aims to collect traffic packets data by using Flume and filter them with Spark Streaming so it is possible to only consider suspicious data related to HTTP Slow Rate Denial-of-Service attacks and reduce the data that will be stored in Hadoop Distributed File System for analysis with the FP-Growth algorithm. With the proposed system, we also aim to address the difficulties in attack detection in cloud environment, facilitating the data collection, reducing detection time and enabling an almost real-time attack detection.

• 한국멀티미디어학회논문지
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• 제20권12호
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• pp.1849-1855
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• 2017

The main purpose of cooperative communications is improvement of communication quality and efficient use of transmission power. In this paper, a cooperative retransmission method is proposed, where neighbor nodes that receive messages correctly between transmit and receive nodes will participate in retransmission of the erroneous packet of the direct link. When the proposed retransmission method is used, the performance of the PER can be greatly improved. In case that the limited information is included in the NACK message, the transmit power of the retransmission packet can be reduced using the proper power control method.

• 한국통신학회논문지
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• 제22권11호
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• pp.2521-2530
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• 1997

In this paepr, we present a video-on-demand (VOD) system design model that address and integrates a number of inter-related issues. Then with analysis and performance evaluation, we investigate various aspects of disk and buffer managements in the given model. Based on the analysis results, we suggest that a distributed buffering scheme with intermediate buffers may te useful to transform bursty disk accesses into a continuous stream for for glitch-free performance of VOD systems. Also, through simulation, we illustrate that massive multimedia information storage design techniques such as prefetching, clustered striping, and real-time disk scheduling integrated with the distributed buffering mechanism may enhance end-to-end real-time performance of VOD systems under wide-area networks.

• 산업기술연구
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• 제26권B호
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• pp.199-206
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• 2006

Internet telephony provides voice communication services with added flexibility for multimedia extension at a lower cost compared to traditional telephone systems. We implemented an internet telephony system as an overlay network without a centralized server, using a distributed hash table (DHT). Compared to the current server-based internet telephony system, our system is fault-tolerant, scalable, and can be flexible extended to various services and advanced to integrated service. To demonstrate the high flexibility of our DHT-based internet telephony system, we made our system cooperate with web servers. Web users can check up others' online stales and establish voice communication sessions to online users at a mouse click. This technology can be applied to more complex services such as multimedia messaging or video conference service.

• 한국멀티미디어학회논문지
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• 제6권6호
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• pp.1071-1078
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• 2003

SOAP(Simple Object Access Protocol)은 분산 환경에서의 정보 교환에 사용되는 분산 컴퓨팅 프로토콜로 분산 시스템간에 메시지를 전달하는 방법, 원격 프로시저 호출/응답을 처리하는 방법을 정의하고 있다 이러한 SOAP 는 텍스트 기 반 XML을 프로토콜로 사용하고 있기 때문에 하드웨어 플렛폼, 운영체제 프로그래밍언어에 독립적으로 사용할 수 있다. 메시지 Broker 시스템은 SOAP을 이용하여 기업과 기업간의 메시지전송을 담당하게 된다. 본 논문에서 SOAP을 기반으로 한 메시지 Broker 시스템을 설계 및 구현하였다. Broker 시스템을 통한 메시지 전송으로 많은 비즈니스 파트너를 통합관리 할 수 있을 것이다.