• Proceedings of the Korea Information Processing Society Conference
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• 2008.11a
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• pp.936-939
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• 2008

차량 내부 네트워크(In-Vehicle Network)에 많은 관심이 고조되는 가운데 Time-Triggered 와 Event-Triggered 패러다임의 장점을 모두 갖춘 하이브리드(Hybrid) 프로토콜인 FlexRay 가 최근 들어 많은 자동차 분야 업체들로부터 주목 받으면서 이에 대한 다양한 성능 분석 시도가 이루어지고 있다. 하지만 FlexRay 프로토콜의 메시지 전송의 유연성(Flexibility)으로 인해 정확한 성능 분석에 많은 어려움이 있다. 이에 본 논문에서는 다양한 길이의 메시지를 고려한 동적 구간 분석 모델을 제안하였고, 이를 바탕으로 잔여 미니 슬롯 확률 분포(Empty Minislot Distribution)를 도출하였으며 FlexRay 메시지 셋(Set)를 이용한 실험을 통하여 특정 길이의 동적 구간에서 미니 슬롯 개수에 따른 잔여 미니 슬롯 발생확률 값의 변화를 확인하였다.

• Proceedings of the Korea Information Processing Society Conference
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• 2005.11a
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• pp.51-54
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• 2005

최근 도로 네트워크 환경에서 날로 증가하는 교통 수요를 충족시키고 각종 교통 문제를 해결하기 위해서 지능형교통시스템(ITS, Intelligent Transportation System)을 적용하고 있다. 특히, 첨단교통정보 시스템(ATIS, Advanced Traveler Information System)은 개별 차량의 주행을 최적화시키는 시스템으로서 운전자에게 출발지에서 목적지까지 빠르고 쾌적한 주행경로를 제공하는 차량 경로계획 수립을 제공한다. 하지만 이러한 시스템은 도로 구간의 비용으로 정적인 값을 이용하므로 동적으로 변화하는 구간 비용을 가지고 도로 네트워크에서 최단 경로를 제공하기는 어렵다. 따라서, 이 논문에서는 교통 혼잡을 고려한 최단 경로 탐색 연산자를 제안한다. 제안된 연산자는 현재 시간 비용과 과거의 시간 비용 변화 량을 더하여 출발지에서 목적지까지 경로를 탐색하는데 이용한다. 이러한 방법은 시간에 따라 변화하는 도로의 상황을 반영하며 출발지에서 목적지까지의 최단 경로뿐만 아니라 예상 도착 시간을 추정할 수 있다. 또한 제안된 연산자는 효율적인 도로 이용, 물류비용 감소, 응급 상황 대체, 연료 절약 및 환경 오염 감소 등의 장점을 가지며 첨단교통정보시스템에서 응용 될 수 있다.

• Journal of Korean Society of Transportation
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• v.32 no.6
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• pp.567-578
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• 2014

The study suggested a method to improve analysis accuracy such that the interactive effects of transportation changes between outside and inside of sub-areas were sequentially considered in the analysis by linking a macroscopic network analysis and a microscopic traffic simulation. A dynamic O/D estimation method was developed for practical implement of sub-area microscopic simulation analysis by using the results of macroscopic network analysis, the results of selected link analysis at the cordon line of the sub-area, departure time data of household travel survey, timely observed traffic volume data at the cordon. This estimated dynamic O/D for the sub-area made it possible to analyze traffic phenomena in details. Various detailed phenomena such as traffic queues, delay at intersection, and conflicts between vehicles, which is impossible to be grasped through a macroscopic analysis, can be analyzed with the dynamic microscopic traffic analysis. Through implementing an empirical study and validation, the study provided a reference result about accuracy of a microscopic traffic simulation of a sub-area to help its application for real transportation policy analysis.

• Convergence Security Journal
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• v.13 no.3
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• pp.25-31
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• 2013

Looking at the recent value change of users and the usage pattern of network users, it is changing from simple web information, one-way information acquisition and data transmission to increase of usage of multimedia, increasing demand for security and customization, and increasing demands for free mobility. Due to this change of demand, the services which were provided individually, developed into a form which is merged, the network also seems to develop into the combined network from the individual network for individual service, and the communication network control technology which is the core technology is also rapidly developing. To reflect the users' demands, the next generation network created the multi-layer network which is based on the WDM/IP transmission system and added the to make it easy to restructure. P-OTS (Packet-Optical Transport System) can be defined as a platform that combines SONET/SDH, Ethernet, DWDM, optical transport network (OTN) switching and reconfigurable optical add-drop multiplexers (ROADMs). In this paper, we suggested that the optimum path choice be performed through diversification of the PCE-based path selection using the information of various layers altogether in the multi-layer environment, compared with the established path selection method when the path was selected using the information of each layers.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.17 no.2
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• pp.488-494
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• 2013

For the activeness and autonomy of a sensor network, the efficient migration method of a mobile agent and the consistent naming services are the required components of a sensor network. Accordingly, this paper presented the implementation of backward migration of an active rule mobile agent applying the naming method based on RMI that used the meta_table including the informations about the components of a sensor network. This study implemented based on the extension of the forward migration[12], and the results of the various experiments present the efficacy of mobile agent middleware system and the possibility of constructing efficient sensor network application environment. And, the results of this study are able to enhance the adaptability on dynamic changes of environment in sensor network application development.

• Journal of KIISE:Information Networking
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• v.28 no.4
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• pp.517-526
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• 2001

In order to reduce the increasing packet loss rates caused by an exponential increase in network traffic, the IETF(Internet Engineering Task Force) is considering the deployment of active queue management techniques such as RED(Random Early Detection). While active queue management in routers and gateways can potentially reduce total packet loss rates in the Internet, this paper has demonstrated the inherent weakness of current techniques and shows that they are ineffective in preventing high loss rates. The inherent problem with these queue management algorithms is that they all use queue lengths as the indicator of the severity of congestion. In this paper, in order to solve this problem, a new active queue management algorithm called MRED(Modified Random Early Detection) is proposed. MRED computes the packet drop probability based on our heuristic method rather than the simple method used in RED. Using simulation, MRED is shown to perform better than existing queue management schemes. To analyze the performance, we also measure throughput of traffics under the FIFO control, and compared the performance with that of this MRED system.

• The Journal of the Korea Contents Association
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• v.18 no.2
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• pp.438-449
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• 2018

Recently, various graph data have been utilized in various fields such as social networks and citation networks. As the graph changes dynamically over time, it is necessary to manage the graph historical data for tracking changes and retrieving point-in-time graphs. Most historical data changes partially according to time, so unchanged data is stored redundantly when data is stored in units of time. In this paper, we propose a graph history storage management method to minimize the redundant storage of time graphs. The proposed method continuously detects the change of the graph and stores the overlapping subgraph in intersection snapshot. Intersection snapshots are connected by a number of delta snapshots to maintain change data over time. It improves space efficiency by collectively managing overlapping data stored in intersection snapshots. We also linked intersection snapshots and delta snapshots to retrieval the graph at that point in time. Various performance evaluations are performed to show the superiority of the proposed scheme.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.23 no.6
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• pp.1025-1035
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• 2013

There has been an explosive increase in the population of OSN(online social network) for 10 years. OSN provides users with many opportunities to have communication among friends, families and goes so far as to make relationships among unknown people having similar belief or interest. However, OSN also produced adverse effects such as privacy breaches, leaking uncontrolled information or disseminating false information. Access control models such as MAC, DAC, RBAC are applied to the OSN to control those problems but those models in OSN are not fit in dynamic OSN environment because user's acts in OSN are unpredictable and static access control imposes burden on users to change access control rules one by one. This paper proposes the dynamic trust-based access control to solve the problems of traditional static access control in OSN.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.9
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• pp.1081-1094
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• 2016

KREONET is a principal national R&E network running by KISTI in Korea. It uniquely provides production research network services for around 200 non-profit research and educational organizations, based on hybrid (IP and non-IP) network infrastructure. However, KREONET is limited to meet various needs of new network services for advanced Science & Technology (S&T) users because its infrastructure is inherently derived form classical hardware-based, fixed and closed environments. So, KREONET-S is designed to provide advanced S&T services to catch up with time-to-research and time-to-collaboration. In this paper, we present a system architecture of KREONET-S based on network infrastructure that consists of data and control planes separately. Furthermore, we propose and describe VDN service which is capable of building a virtual dedicate & bandwidth-guaranteed network for S&T group dynamically. we implement VDN application on KREONET-S and then perform performance analysis for proving that KREONET-S system and VDN application can be a good solutions to cope with new network paradigms for various advanced S&T applications and users.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.4A
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• pp.309-315
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• 2009

Wireless Ad-hoc networks are dynamic networks that consist of mobile nodes. Nodes in Ad-hoc networks are usually laptops, PDAs or mobile phones. These devices feature Bluetooth and/or IEEE 802.11 (WiFi) network interfaces and communicate in a decentralized manner. Due to characteristics of Ad-hoc networks, Mobility is a key feature of routing protocol design. In this paper, we present an enhanced routing maintenance scheme that cope with topology changes pre-actively. The key feature of the proposed scheme is to switch next-hop node to alternative neighbor node before link breakage for preventing route failure. From extensive experiments by using NS2, the performance of the proposed scheme has been improved by comparison to AODV protocol.