• Journal of Information Processing Systems
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• v.6 no.3
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• pp.413-434
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• 2010

Wireless sensor networks are usually characterized by dense deployment of energy constrained nodes. Due to the usage of a large number of sensor nodes in uncontrolled hostile or harsh environments, node failure is a common event in these systems. Another common reason for node failure is the exhaustion of their energy resources and node inactivation. Such failures can have adverse effects on the quality of the real-time services in Wireless Sensor Networks (WSNs). To avoid such degradations, it is necessary that the failures be recovered in a proper manner to sustain network operation. In this paper we present a dynamic Energy efficient Real-Time Job Allocation (ERTJA) algorithm for handling node failures in a cluster of sensor nodes with the consideration of communication energy and time overheads besides the nodes' characteristics. ERTJA relies on the computation power of cluster members for handling a node failure. It also tries to minimize the energy consumption of the cluster by minimum activation of the sleeping nodes. The resulting system can then guarantee the Quality of Service (QoS) of the cluster application. Further, when the number of sleeping nodes is limited, the proposed algorithm uses the idle times of the active nodes to engage a graceful QoS degradation in the cluster. Simulation results show significant performance improvements of ERTJA in terms of the energy conservation and the probability of meeting deadlines compared with the other studied algorithms.

• KNOM Review
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• v.22 no.2
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• pp.12-21
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• 2019

There is a rapid development of experimental equipment and ICT technology in data-intensive scientific areas, thus, big data of more than exabyte size is being generated. However, the big data transmission technology does not satisfy the needs of the application researchers who utilize it. Various high-performance transmission technologies have been developed based on QoS(Quality of Service), but they also require changes in the clean slate method. On the other hand, ScienceDMZ technologies improve the performance of scientific big data transmission by bypassing the firewall that causes a big problem in transmission performance. In addition, it is possible to implement without changing the existing network. In this paper, we built ScienceDMZ in an international long-distance environment based on KREONET(Korea Research Environment Open NETwork), and we verified the performance. We also introduced how GPU platform could be linked in a distributed ScienceDMZ environment.

• The KIPS Transactions:PartC
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• v.14C no.1 s.111
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• pp.27-38
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• 2007

IPv6 has appeared for solving the address exhaustion of IPv4 and for guaranteeing the problems of security and QoS. It occurs the unexpected new attacks of IPv6 as well as the existing attacks of IPv4 because of the increasing address space to 128bits and the address hierarchies for efficient network management and additions of the new messages between nodes and routers like neighbor discovery and auto address configuration for the various comfortable services. For the successful transition from IPv4 to IPv6, we should get the secure compatibility between IPv4 hosts or routers working based on secure and systematic policy and IPv6. Network manager should design security technologies for efficient management in IPv4/IPv6 co-existence network and IPv6 network and security management framework designation. In this paper, we inspected the characteristics of IPv4 and IPv6, study on security requirement for efficient security management of various attacks, protocol, service in IPv4/IPv6 co-existence and IPv6 network, and finally suggest integrated solution about security vulnerability of IPv6 network in considering of analysis of IPv6 system, host and application, IPv6 characteristics, modified CGA(MCGA).

• The KIPS Transactions:PartC
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• v.12C no.3 s.99
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• pp.457-464
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• 2005

This paper describes an Adaptive Context-aware Service (ACS) using Model Driven Architecture (MDA)-based Service Creation Environment (SCE) on PARLAY X based service delivery platform in ubiquitous computing environments. It can be expected that both the context-awareness and adaptation in ubiquitous computing environments will be deployed. But the existing context-aware middleware lacks in considering adaptation. Therefore, the object of this paper is to support the architecture and the Application Programming Interface (API) of the network service for both the context-awareness and adaptation in ubiquitous computing environment. ACS is to provide users with the adaptive network service to the changing context constraints as well as detecting the changing context. For instance, ACS can provide users with QoS in network according to the detected context, after detecting the context such as location and speed. The architecture of ACS is comprised of a Service Creation Environment (SCE), Adaptive Context Broker and PARLAY gateway. SCE is to use Context-based Constraint Language (CCL) for an expression of context-awareness and adaptation. Adaptive Context Broker is to make a role of the broker between SCE and PARLAY G/W. PARLAY G/W is to support API for PARLAY X-based service delivery platform.

• Journal of Communications and Networks
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• v.6 no.3
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• pp.280-286
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• 2004

The widespread use of the Internet and the maturing of digital video technology have led to an increase in various streaming media application. However, new classes of hosts such as mobile devices are gaining popularity, while the transmission became more heterogeneous. Due to the characteristics of mobile networks such as low speed, high error bit rate, etc., the applications over the wireless channel have different needs and limitations from desktop computers. An intermediary between two communicating endpoints to hide the heterogeneous network links is thought as one of the best approaches. In this paper, we adopted the concept of inter-packet gap and the sequence number between continuously received packets as the error discriminator, and designed an adaptive packet sizing mechanism to improve the network efficiency under varying channel conditions. Based on the proposed mechanism, the packetization scheme with error protection is proposed to scalable encoded video delivery. Finally, simulation results reveal that our proposed mechanism can react to the varying BER conditions with better network efficiency and gain the obvious improvement to video quality for stored MPEG-4 FGS video delivery.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.4 no.3
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• pp.341-357
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• 2010

Forward Error Correction (FEC) techniques have been adopted to overcome packet losses and to improve the quality of video delivery. The efficiency of the FEC has been significantly compromised, however, due to the characteristics of the wireless channel such as burst packet loss, channel fluctuation and lack of Quality of Service (QoS) support. We propose herein an Adaptive Cross-layer FEC mechanism (ACFEC) to enhance the quality of video streaming over 802.11 WLANs. Under the conventional approaches, FEC functions are implemented on the application layer, and required feedback information to calculate redundancy rates. Our proposed ACFEC mechanism, however, leverages the functionalities of different network layers. The Automatic Repeat reQuest (ARQ) function on the Media Access Control (MAC) layer can detect packet losses. Through cooperation with the User Datagram Protocol (UDP), the redundancy rates are adaptively controlled based on the packet loss information. The experiment results demonstrate that the ACFEC mechanism is able to adaptively adjust and control the redundancy rates and, thereby, to overcome both of temporary and persistent channel fluctuations. Consequently, the proposed mechanism, under various network conditions, performs better in recovery than the conventional methods, while generating a much less volume of redundant traffic.

• Journal of the Korean Institute of Intelligent Systems
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• v.20 no.1
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• pp.7-14
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• 2010

In this paper, we introduce a hierarchical internet application traffic classification system based on SVM as an alternative overcoming the uppermost limit of the conventional methodology which is using the port number or payload information. After selecting an optimal attribute subset of the bidirectional traffic flow data collected from the campus, the proposed system classifies the internet application traffic hierarchically. The system is composed of three layers: the first layer quickly determines P2P traffic and non-P2P traffic using a SVM, the second layer classifies P2P traffics into file-sharing, messenger, and TV, based on three SVDDs. The third layer makes specific classification of the entire 16 application traffics. By classifying the internet application traffic finely or coarsely, the proposed system can guarantee an efficient system resource management, a stable network environment, a seamless bandwidth, and an appropriate QoS. Also, even a new application traffic is added, it is possible to have a system incremental updating and scalability by training only a new SVDD without retraining the whole system. We validate the performance of our approach with computer experiments.

• The Journal of the Korea Contents Association
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• v.8 no.9
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• pp.42-54
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• 2008

In recent years, embedded systems have been expanding their application domains from traditional embedded systems such as military weapons, robots, satellites and digital convergence systems such as celluar phones, PMP(Portable Multimedia Player), PDAs(Personal Digital Assistants) to Next Generation Personal Computers(NGPCs) such as eating PCs, wearable computers. The NGPCs are network-based, human-centric digital information devices diverged from the traditional PCs used mainly for document writing, internet searching and database management. Wearable computers with battery capacity and memory size limitations have to use real-time operating systems with small footprints and low power management techniques to provide user's QoS in spite of hardware constraints. In this paper, we have designed and implemented a low-power RTOS (called eRTOS) for wearable computers. The implemented eRTOS has 18KB footprints and the dynamic power management and the device power management schemes are adapted in it. Experimental results with wearable computer applications show that the low power techniques could save energy up to 47 %.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.26 no.5A
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• pp.828-835
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• 2001

인터넷 이용이 폭발적으로 증가하고, 음성, 데이터는 물론 영상을 포함한 멀티미디어 정보의 요구가 급증함에 따라 21세기의 통신 네트워크는 통신과 방송의 융합, 과대역화, 고속화, 대용량화, 지능화, 개인화로 바뀌고 있다. 이와 같은 초고속 서비스 망의 중심에는 ATM 기술이 위치하고 있으며, 아직까지 ATM과 같이 진정한 의미의 QoS를 보장할 수 있는 기술은 없는 것으로 알려져 있고, 또한 ATM은 네트워크 응용의 타입을 스스로 인식해 가장 알맞은 대역폭을 제공하므로 실시간 전송 데이터에 대해 가장 효율적으로 대응할 수 있는 기술이다. 이 논문에서는 초고속 위성통신과 발전전망의 세계적인 동향을 분석하고 이에 적합한 응용 서비스를 제공하는 모형을 제시한다.

• Electronics and Telecommunications Trends
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• v.21 no.5 s.101
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• pp.1-10
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• 2006

향후 인터넷 기반 애플리케이션에는 확장성, 보안 및 신뢰성, 새로운 서비스에 대한 유연성 및 QoS 등의 요구사항이 제시된다. 기존 클라이언트-서버 방식에서 이러한 요구사항의 만족을 위해서는 복잡성 및 고비용 문제가 제기된다. 반면, 모든 형태의 분산 자원 접근이 가능한 P2P 통신 방식에서는 보다 간단한 해결방안을 제시함으로써 인터넷기반 애플리케이션에 새로운 가능성을 제시하고 있다. 본 고에서는 P2P 기술에 대한연구 개발 및 응용 서비스 동향에 대해여 소개한다. 또한 유비쿼터스 환경에서 P2P 기술의 역할 및 해결되어야 할 문제점에 대해서 정리하고, 실제 P2P를 이용한 유비쿼터스홈 구축 모델을 제시한다. 마지막으로 향후 P2P 요소 기술 및 응용서비스 발전 전망에 대해 간략히 살펴본다.