• Proceedings of the Korea Multimedia Society Conference
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• 2000.11a
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• pp.45-48
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• 2000

본 논문은 현재 고성능 가역압축 부호화의 표준이 되는 JPEG-LS의 예측오차에 대한 확률분포를 결정하는 컨텍스트 모델링(context modelling)에서 컨텍스트 정수의 결정 방법에 관해 기술한다. 먼저, 압축률 향상을 위해 낮은 대비(low contrast)를 적용하는 전처리 과정을 도입한다. 둘째로, 낮은 복잡도(low complexity)를 위해 주목화소와 주변화소 사이의 차분을 양자화하고, 그 값 Q$_1$,Q$_2$, Q$_3$로부터 컨텍스트 정수(Q)의 결정을 위해 우선 순위를 정한 후, 3차원 가상좌표 위로의 할당을 고려한다. 또한, 제안 방법과 JPEG-LS의 near-lossless부분을 비교하여, 다양한 영상에 대하여 적용시켜 본 결과, 제안한 방법의 압축률과 손실이득이 훨씬 좋음을 보인다.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.36S no.5
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• pp.1-11
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• 1999

유선망이 ISDN/B-ISDN으로 확장되고, 서비스도 음성에서 데이터, 영상 등의 멀티미디어로 통합 및 발전됨에 따라 무선망에서의 가입자 서비스 요구도 유선망과 대등한 수준으로 확대될 것이다. 이러한 무선 ATM망은 초기 사설망으로부터 서비스가 도입되기 시작하여 마이크로 셀을 기반으로 한 공중망으로 확장되어, 궁극적으로 유무선 통합 transparent 망으로 발전하게 될 것이다. 무선 ATM 망에서는 한정된 무선 자원을 이용하여 다양한 응용 서비스를 효율적으로 제공할 수 있는 다중접속 프로토콜을 필요로 한다. 본고에서는 먼저 현대 MBS에서 연구되고 있는 단일 및 다중 동적슬롯할당 기법을 소개하고 다양한 소스 트래픽에 대한 시뮬레이션을 통해 문제점을 분석하였으며, DSA 프로토콜의 단점을 개선한 두가지 방안의 충돌 해결 알고리즘을 제안하고 동질 및 이질 트래픽에 대한 성능을 비교 검토하였다. 제안된 알고리즘을 이용하여 연결상태에 있는 가상채널의 개수가 증가할수록 시스템 전체의 지연 성능을 현저하게 개선하였다.

• The Journal of Information Technology
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• v.5 no.2
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• pp.27-34
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• 2002

The KVM garbage collector implemented in CLDC was generally based on the simple mark-sweep algorithm, but it is difficult to handle objects of varying size without fragmentation of the available memory. In this paper, we have designed and implemented a memory allocator based on the mark-sweep algorithm that minimizes the fragmentation by the method that determines the allocation position of free-space list according to object size. The experimental result shows that our algorithm reduce the fragmentation and improve the execution time than the existing algorithm.

• Annual Conference of KIPS
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• 2015.10a
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• pp.1625-1627
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• 2015

클라우드 컴퓨팅의 가상화된 인프라 기반 위에서 IT 자원 및 애플리케이션 서비스를 관리하고 배포하는 작업이 클라우드 프로비저닝이다. 본 논문에서는 IT 자원을 할당함에 있어 전문적인 지식을 가진 관리자의 개입을 최소화하기 위해 일련의 자원 할당 작업을 자동화하였다. 자동화된 자원 프로비저닝을 통해 관리자는 특정 전문 지식 없이도 자원 할당 및 배포가 가능해져 이용자의 요구를 보다 신속하게 처리할 수 있게 되었다.

• Annual Conference of KIPS
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• 2009.04a
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• pp.792-795
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• 2009

클라우드 컴퓨팅은 인터넷 기술을 활용하여 다수의 고객들에게 높은 수준의 확장성을 가진 IT 자원들을 서비스로 제공하는 컴퓨팅이다. 데이터 센터내의 가상화된 스토리지를 할당 받아 개인의 PC 환경처럼 사용하는 클라우드 컴퓨팅 환경 에서 사용자들은 자신의 데이터가 저장된 위치, 현재 리소스 사용률 등의 정보를 필요로 한다. 그러나 현재 클라우드 컴퓨팅 환경에서는 이런 정보들을 사용자에게 서비스하지 않는다. 따라서 본 논문에서는 데이터 센터내의 할당 받은 사용자의 스토리지 리소스 사용량, 서비스 정보, 데이터 전송률을 모니터링 하여 실시간으로 서비스 해주는 클라우드 컴퓨팅 환경에서 사용자를 위한 모니터링 서비스를 제안한다.

• Journal of KIISE:Computing Practices and Letters
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• v.8 no.4
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• pp.411-422
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• 2002

Recently, there have been active researches about the VPCS (Virtual Parallel Computing System) based on multiple agents. The PVCS uses personal computers or workstations that are dispersed all over the internet, rather than a high-cost supercomputer, to solve complex problems that require a huge number of calculations. It can be made up with either homogeneous or heterogeneous computers, depending on resources available on the internet. In this paper, we propose a new method in order to distribute worker agents and work packages efficiently on the VPCS based on the IBM Aglets. The previous methods use mainly the master-slave pattern for distributing worker agents and work packages. However, in these methods the workload increases dramatically at the central master as the number of agents increases. As a solution to this problem, our method appoints worker agents to distribute worker agents and workload packages. The proposed method is evaluated in several ways on the VPCS, and its results are improved to be worthy of close attention as compared with the previous ones.

• Journal of KIISE
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• v.43 no.12
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• pp.1404-1411
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• 2016

Network virtualization is a technique that abstracts the physical network to provide multiple virtual networks to users. Virtualized network has the advantage to offer flexible services and improve resource utilization. In SDN architecture, network hypervisor serves to virtualize the network through address virtualization, topology virtualization and policy virtualization. Among them, address virtualization refers to the technique that provides an independent address space for each virtual network. Previous work divided the physical address space, and assigned an individual division to each virtual network. Each virtual address is then mapped one-to-one to a physical address. However, this approach requires a lot of flow entries, thus making it disadvantageous. Since SDN switches use TCAM (Ternary Contents Addressable Memory) for the flow table, it is very important to reduce the number of flow entries in the aspect of cost and scalability. In this paper, we propose a LISP based address virtualization, which separates address spaces for the physical and virtual addresses and transmits packet through tunneling, in order to resolve the limitation of the previous studies. By implementing a prototype, we show that the proposed scheme provides better scalability.

• Journal of the Korea Society for Simulation
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• v.22 no.1
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• pp.77-86
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• 2013

Cloud computing is one of the distributed computing environments and utilizes several computing resources. Cloud environment uses a virtual machine to process a requested job. To balance a workload and process a job rapidly, cloud environment uses a provisioning technique and assigns a task with a status of virtual machine. However, a scheduling method for cloud computing requires a definition of virtual machine availabilities, which have an obscure meaning. In this paper, we propose Fuzzy logic driven Virtual machine Provisioning scheduling using Resource Evaluation(FVPRE). FVPRE analyzes a state of every virtual machine and actualizes a value of resource availability. Thus FVPRE provides an efficient provisioning scheduling with a precise evaluation of resource availability. FVPRE shows a high throughput and utilization for job processing on cloud environments.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.11
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• pp.4592-4596
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• 2010

This paper is related to the method for sharing some remote devices through USB/IP on the connected system environment. Sharing the remote devices is actually based on the connection technology using USB which is one way of access methods on virtualized server environment. The users who receive server computing unit might want to connect to remote allocated server with the local devices. We can solve the problem of the access methods related to the sharing devices through USB device emulation. This paper discusses the implementation of USB emulation which is based on personalized services on virtualized server environment. Like this, this paper will share devices on the level of USB device. This research can write to the device directly due to virtualizing the device level.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.26 no.9
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• pp.1320-1329
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• 2022

Currently, advanced national research network groups are continuously conducting R&D for the requirement to provide SDN/NFV-based network automation and intelligence technology for R&E users. In addition, the requirement for providing large-scale data transmission with the high performance networking facility, compared to general network environments, is gradually increasing in the advanced national research networks. Accordingly, in this paper, we propose an open API-based virtual network provisioning automation platform for large data transmission researched and developed to respond to the networking requirements of the national research network and present the implementation results. The platform includes the KREONET-S VDN system that provides SDN-based network virtualization technology, and the Kubernetes system that provides container-oriented server virtualization technology, and the Globus Online, a high-performance data transmission system. In this paper, the environment configurations, the system implemetation results for the interworking between the heterogeneous systems, and the automated virtual network provisioning implementation results are presented.