• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.8B
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• pp.514-524
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• 2005

In optical burst switching(OBS) networks, the ingress edge router assembles packets in the same class queue into the appropriate size of burst. A burst control packet(BCP) is generated for channel reservation of corresponding data burst and sent earlier than the corresponding data burst with an offset time. Offset time is determined considering the number of hops from source to destination and the required quality of service(QoS). After offset time, the burst data is passed through tile pre-configured optical switches without any O/E/O conversion. But a failure in OBS networks may lead to the loss of bursts until the ingress nodes receive the failure indication signal. This results in a significant degradation in QoS. Therefore, in this paper, we propose a fault-tolerant node architecture based on sub-carrier multiplexing to reduce the effects of failure in OBS networks. The Performance of the proposed fault-tolerant node architecture exhibits considerable improvement as compared with the previous ones.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.9B
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• pp.777-784
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• 2006

In this paper, we propose the PON-based access network based on conventional TDM-PON architecture, which utilizes WDM wavelength channel and bandwidth dynamically. It is also described a dynamic MAC protocol in order to increase the number of subscribers and efficiency of resource utilization. Of particular importance in the proposed approach for MAC protocol is that the wavelength channel and time slot for up/downlink is dynamically allocated according to the required QoS level and the amount of data in data transmission, through the dedicated control channel between OLT and ONU. We evaluate the performance of average packet end-to-end delay in a statistical analysis and numerical analysis. In addition, through simulations with various traffic models, we verified the superior performance of the proposed approach by comparing with the results of other E-PONs.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.42 no.4
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• pp.758-767
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• 2017

IoT paradigm which makes a information without direct intervention of a human and interworks with other objects, humans and systems is attracting attention. It will be expected the number of smart devices equipped with sensors and wireless communication capabilities is reached to about 260 billion by 2020. With the vast amount of sending data generated from rapidly increasing number of smart devices, it will bring up the traffic growth over internet and congestion in wireless networks. In this paper, we utilize the smart device as a sink node to collect and forward the sensing data periodically in IoT and propose a heuristic algorithm for a selection of sink nodes' set with each sink node satisfies the QoS its applications because a selection of optimal sink nodes' set is NP-hard problem. The complexity of proposed heuristic algorithm is $O(m^3)$ and faster than the optimal algorithm.

• Proceedings of the KIEE Conference
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• 2002.07d
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• pp.2794-2796
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• 2002

기업 네트워크에서 안전하고 효과적이며 안정된 망 운영관리 환경 제공은 당면한 중요과제이며 기업 경쟁력의 핵심인 정보기술을 통한 생산성과도 연계성을 갖고 있다. 특히 전력통신망의 경우 전자메일, 회계관리, 전자결재, 도면자료관리 등의 데이터 통신망에서부터 IBM 온라인, 사내 방송망, 전력계통설비 원방 제어용 시스템들 간을 연결하는 EMS, SCADA 등 전력 수급용 전용 통신망에 이르기까지 다양한 종류의 통신망이 구축 운용되고 있다. 이러한 기업환경에 따라 네트워크를 효율적으로 관리하기 위한 네트워크 관리 시스템에 대한 관심이 증대되고 있으며 많은 네트워크 관리 시스템들이 도입되어 운영되었으나 이들 관리 시스템들은 모니터링에 의한 통계값 제공과 같은 단순 평면적인 관리 기능만을 제공한 뿐 네트워크의 특성과 환경에 따른 분석, 진단 기능은 제공하지 못하고 있다. 이와 더불어 네트워크 관리자는 보다 손쉬운 방법으로 네트워크를 관리하고자 하며, 보다 지능적이고 효율적으로 관리하고자 한다. 하지만 관리 시스템이 모든 네트워크에 대해 효율적이고 지능적인 관리 기능을 제공하기는 매우 어려우며 이는 장기간의 관리 네트워크의 특성과 트래픽 형태를 파악한 후에나 가능하다. 결국 지능적이고 효율적인 네트워크 관리는 네트워크의 특성과 함께 이전에 관리자에 의해서 내려졌던 관리 행위 및 의견 그리고 조치에 대한 이력정보를 학습하고 있을 때만 가능하다. 본 논문은 전력통신망을 대상으로 전력통신망이 지닌 네트워크 특성을 반영하며 네트워크 운영 과정에서 축적된 관리자의 의견과 이에 대한 조치를 지식 데이터베이스화하여 지능적인 관리 시스템을 제공하기 위한 기반 시스템으로써 전력통신망 운용 관리 지원시스템을 설계 및 구현하였다. 본 시스템은 향후 지식 정보를 학습하고 이를 바탕으로 논리적인 추론을 통해 관리 네트워크를 지능적이고 자동적으로 관리할 수 있는 시스템으로 확대 개발될 것이다.

• Journal of the Korea Society for Simulation
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• v.17 no.4
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• pp.153-158
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• 2008

The technology of Software Defined Radio (SDR) is a possible solution to interwork flexibly between various wireless transport protocols. Ubiquitous network, like u-health service network, includes sensor devices or nodes which do not facilitate all the same transport protocols to access network. As such this may be in such unreachable situations as poverty of all required AP (Access Point)’s, faults or contention in a path of particular protocol communication, etc. This paper presents research results of modeling and simulation to analyze transport performance of multi-protocol ubiquitous network which includes SDR-based interwork nodes and congestion-controlled AP’s. Focusing mainly on dynamics of overall transport performance rather than protocol execution procedures, this paper employs the Zeigler’s DEVS (Discrete Event Systems Specification) methodology and DEVSim++simulation environment to experiment.

• Journal of Digital Convergence
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• v.14 no.1
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• pp.171-179
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• 2016

The energy consumption problem in wireless sensor networks is investigated. The problem is to expend as little energy as possible receiving and transmitting data, because of constrained battery. In this paper, in order to extend the lifetime of the network, we proposed a location-based clustering algorithm for wireless sensor network with skewed-topology. The proposed algorithm is to deploy multiple child nodes at the sink to avoid bottleneck near the sink and to save energy. Proposed algorithm can reduce control traffic overhead by creating a dynamic cluster. We have evaluated the performance of our clustering algorithm through an analysis and a simulation. We compare our algorithm's performance to the best known centralized algorithm, and demonstrate that it achieves a good performance in terms of the life time.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2013.10a
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• pp.150-153
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• 2013

By the development of IT, most business has been processed on the IT solution-based servers has increased Therefore, the importance of security of the server is highlighted. And the need for password management server efficient and safe is raised. There is a need to change at least 8 characters to mix the numbers and letters and password change passwords on a regular basis, you need a password for each system account is set in a different way, but the continuation of the system there is a tendency to password problems occur problems caused by the limits of the introduction of human resources and introduction basis occurs. The password management feature, though it is expensive is partially providing integrated access control solutions at home and abroad, there is a drawback that stresses the traffic on the server. Future, we conducted a study of password management solutions for the server of the server is determined IT transformation trend of non-IT field to accelerate, is continuously increasing it accordingly.

• The Journal of the Korea Contents Association
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• v.3 no.4
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• pp.38-47
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• 2003

Distributed problem solving is the cooperative solution of problem by a decentralized and loosely couped collection of knowledge-sources (KS's), located in a number of distinct processor nodes. The contract net protocol has been developed to specify problem-solving communication and control for nodes in a distributed problem solver. Task distribution is affected by a negotiation process, a discussion carried on between nodes with tasks to be executed and nodes that may be able to execute tasks In this paper, we present the coordination method among distributed intrusion detection system and firewall by the contract net protocol. The method enhances the intrusion detection performance and provides the communication methods. To mode IDS and firewall, security models hue been hierarchically constructed based on the DEVS (Discrete Event system Specification) formalism. Each ID agent cooperates through the contract net protocol for detecting intrusions. The IDS which detects the intrusion informs to firewall, so the harmful network traffic is blocked. If an agent detects infusions, the agent transfers attacker's information to a firewall. Using this mechanism attacker's packets detected by In can be prevented from damaging the network.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.38 no.1
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• pp.1-13
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• 2001

In this paper, we propose a new dynamic bandwidth allocation and call admission control for VBR video sources with QoS constraints to support an efficient resource management and at the same Lime to satisfy the user's quality or service requirements. For the dynamic bandwidth allocation, first the next amount of traffic is predicted using a modified adaptive linear prediction method that considers abrupt scene change effects. And then, we dynamically allocate the necessary bandwidth to each connection based on the currently provided quality degree by the network with respect to the user's QoS requirements in terms of average delay and loss ratio. For the admission control, we determine the acceptance or rejection or a new connection based on the quality satisfaction degrees of the existing connections. Simulation results show that our proposed dynamic schemes are able to provide a stable service, which well meets the user's quality requirements.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.46 no.2
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• pp.104-113
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• 2009

Recently, high-speed Internet users and broadband network infrastructure are increasing. However, the TCP protocol widely used in the Internet is an appropriate transport only for the legacy Internet, it is inefficient for traffic transport for network environments with large bandwidth-delay product. In order to remedy this problem, there have been many researches about improved congestion control algorithms for broadband networks. In these studies, most of performance evaluation has been done by simulations. In this paper, after we reviewed the proposed high bandwidth transport layer protocols, we implemented a real testbed, measured the performance and analyzed the problems of high-speed transport protocols through the international research network TEIN2 between three nations, Korea, China, and Germany.