• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.10
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• pp.4902-4932
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• 2016

The popularity of network virtualization has recently regained considerable momentum because of the emergence of OpenFlow technology. It is essentially decouples a data plane from a control plane and promotes hardware programmability. Subsequently, OpenFlow facilitates the implementation of network virtualization. This study aims to provide an overview of different approaches to create a virtual network using OpenFlow technology. The paper also presents the OpenFlow components to compare conventional network architecture with OpenFlow network architecture, particularly in terms of the virtualization. A thematic OpenFlow network virtualization taxonomy is devised to categorize network virtualization approaches. Several testbeds that support OpenFlow network virtualization are discussed with case studies to show the capabilities of OpenFlow virtualization. Moreover, the advantages of popular OpenFlow controllers that are designed to enhance network virtualization is compared and analyzed. Finally, we present key research challenges that mainly focus on security, scalability, reliability, isolation, and monitoring in the OpenFlow virtual environment. Numerous potential directions to tackle the problems related to OpenFlow network virtualization are likewise discussed.

• Electronics and Telecommunications Trends
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• v.10 no.2 s.36
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• pp.59-71
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• 1995

본 고에서는 디렉토리 기술이 도입된 세대별 지능망의 표준화 동향을 분석한다. 국제전기통신연합 전기통신표준화 분야(ITU-T)의 지능망 관련 표준화를 제 1세대, 제 1세대 보강, 제 2세대, 제 3세대, 최종적인 지능망 형태 등으로 구분하여 비교분석 하였으며, 지능망이 도입되면서 제공되는 종합 개인 통신 (UPT)을 설명하고, 종합 개인 통신을 위해 디렉토리 기술이 필요한 이유와 디렉토리의 표준화 동향을 분석하고, 지능망과 종합 개인 통신, 디렉토리 등과의 관계를 분석, 설명하였다.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.5
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• pp.18-24
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• 2013

Network coding has been extensively studied to increase the network throughput by exploiting the broadcast and overhearing capabilities. In this paper, we formulate a network utility maximization problem to improve the network utility in multichannel, multiradio and multisession wireless multihop network with intrasession network coding. To find the solution of this problem, we propose a congestion control, distributed rate control, and heuristic resource allocation algorithm. We find the network utility and evaluate the performance in multichannel, multiradio and multisession environment by using MATLAB. Finally, the results show that the proposed schemes can achieve throughput improvement by performing the network utility optimization in wireless multihop network.

• The Transactions of the Korea Information Processing Society
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• v.6 no.3
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• pp.729-741
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• 1999

ATM networks are widely deployed as the network that is capable of supporting multimedia services efficiently now. To date, a large portion of ATM connections, particularly in the WAN environment, have been of a permanent virtual circuits-requiring management intervention for set-up and tear-down. However, switched virtual circuits are required to support a range of desired characteristics on demand, to a reachable end user. To establish, maintain and release on-demand call/connections, the user-network interface(UNI) and node-node interface(NNI) signalling capabilities are required. Two protocols have been specified for NNI signalling within a public network: the broadband integrated-services user part(B-ISUP) protocol specified by the ITU-T, and the private network-network interface(PNNI) protocol specified by the ATM Forum. PNNI offers different type of internetwork or internodal interface from the traditional B-ISUP approach favored to date public network operators. In spite of its name, PNNI may find its place in network service provide networks as well as in private networks. Thus many public network operators and ATM equipment manufacturers are still unable to choose the NNI interface architecture of their system. In this paper, we survey the characteristics of the B-ISUP and PNNI protocols, and investigate the applicability issue of these specifications to the ATM-based Information Infra-Network of Korea. Analyzing the characteristics of the two protocols and clarifying the NNi requirements of the ATM-based Information Infra-Network of Korea, we propose that the B-ISUP protocol is more suitable than PNNI.

• Journal of Korea Multimedia Society
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• v.11 no.2
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• pp.214-227
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• 2008

As cellular network technologies continue to evolve, various network standards coexist in most CDMA-based cellular networks. This means that mobile device users access mobile services over different network bandwidths according to the users' positions or the mobile devices' network access capabilities. Such differences of network bandwidths cause big differences in service response times. To address this problem, we present a framework called CANS (Context-Aware framework for mobile Navigation Services), which takes into account the user's network profile to adapt the contents for CDRG(Centrally Determined Route Guidance) navigation services for cellular phones. To the best of the authors' knowledge, CANS is the first context-aware framework to make mobile navigation services more feasible. The experimental results under commercial CDMA network show that CANS is able to provide similar service response times regardless of type of wireless network to which users connect by adapting the contents to network bandwidths.

• The Journal of the Korea Contents Association
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• v.16 no.5
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• pp.205-216
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• 2016

This study aimed to discover the most influential player in the network of Soccer game and how individual players contribute within the team with quantitative capabilities they possess. It also examined whether or not the network of relationship between players and the coach's tactics were in harmony. The results showed high level of correlation between the network between offenders and defenders according to tactics of the coach during the first half. It can be said that each players fulfilled their role and formed a network within them to lead the game and form a virtuous network structure. On the other hand, the overall network of the team was focused on a specific player during the second half. But the coach's appropriate use of substitutes and change in tactics stabilized the network balance between the players.

• Proceedings of the KIEE Conference
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• 2004.11c
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• pp.657-659
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• 2004

CAN is a serial communication bus for real-time controls and automations in distributed control systems. In distributed control systems, occasionally a sensor module and a controller are not in the same node and physically separated. In order for the signal from a sensor node to reach the controller node, the signal must travel through network. CAN has a certain capabilities to deal with real-time data. However, when many nodes on the networks try to send data on the same network, the arbitration mechanism to solve the data collision problem is necessary. This situation causes the time delay which has detrimental effects on the performance of the control systems. This paper proposes a method to solve the problem due to the time delay in distributed control system using CAN. Time delay is approximated to an element with a rational transfer function using Pade approximation and Mu~synthesis method is applied. Since time delay in the network is not constant, the time delay element is considered to be an uncertainty block with a bound. The proposed method is applied to the experimental system with CAN and proved to be effective.

• Journal of Information Technology Services
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• v.19 no.1
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• pp.1-16
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• 2020

Suncheon City Regeneration Project is known as the concept of cultural residents. Through the previous projects, the residents' capabilities have been improved, and the projects have been carried out according to their strategies. For this reason, participants in urban regeneration projects are important. The purpose of this study is to actually identify the 'rescue center' and 'direct relationship' with the analysis utilizing the characteristics of social networks NetMiner solution of the participants, who led the project, Suncheon. Surveys and interviews were conducted for participants, and the characteristics of social networks were analyzed in time series to quantify and visualize the results. As a result of the analysis, social networks were changed among the participants before and after the urban regeneration project. Initially, loose networks were denser over time, and initially networks formed only around participants were expanded over time. Network analysis has revealed that the system is strengthening with urban regeneration projects in the form of public and public-private cooperation. This highlights the need for a city-centered urban regeneration strategy centered on people and shows that a dense network of participants can be a success factor.

• Korean Journal of Oriental Medicine
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• v.16 no.2
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• pp.91-99
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• 2010

In this paper, we designed and implemented a semantic social network system in Korea Institute of Oriental Medicine (abbreviated as KIOM). Our social network system provides the capabilities such as tracking search, ontology reasoning, ontology graph view, and personal information input, update and management. Tracking search provides the search results by the research information of relevant researchers using ontology, in addition to those by keywords. Ontology reasoning provides the reasoning for experts, mentors, and personal contacts. Users can easily browse the personal connections among researchers by traversing the ontology by graph viewer. These allows KIOM researchers to search other researchers who could aid the researches and to easily share their research information.

• The KIPS Transactions:PartA
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• v.16A no.6
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• pp.489-500
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• 2009

Robots have limited computing resources and robot services have different requirement such as sensors, actuators, computational capabilities and timeliness. In this paper, we propose a dynamic management method of service execution contexts to perform various services efficiently and to meet the time constraint of service in network-based robots. The proposed method is tested in the real network-based robot system. The results show that the real-time requirement for services is satisfied and the resource utilization is improved. The proposed method provides the extendability and flexibility of sensors and services by aptly modifying service execution contexts and increases the reusability of service.