• Journal of the Korea Institute of Information Security & Cryptology
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• v.17 no.6
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• pp.65-76
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• 2007

The P2P file sharing system sends the results to users by searching the files in the shared folders. In the process of it, the problem is that the transferred information includes the pathname and file information and it can be revealed who searches which files. In related to this problem, anonymous file sharing P2P protocol has been an active research area where a number of works have been produced. However, the previous studies still have a few of weakness. Therefore, We propose two anonymous P2P file sharing protocols based on the decentralized and unstructured Random Walk. The first scheme uses the dynamic onion routing where the requester can receive the wanted file without knowing other peers' IDs. The second scheme uses the IP multicast method which lowers the computational overhead. Both of them are more suited for the dynamic P2P system.

• Journal of KIISE:Information Networking
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• v.30 no.3
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• pp.329-342
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• 2003

Most of the existing multicast routing protocols for ad-hoc networks do not take into account the efficiency of the protocol for the cases when there are large number of sources in the multicast group, resulting in either large overhead or poor data delivery ratio when the number of sources is large. In this paper, we propose a multicast routing protocol for ad-hoc networks, which particularly considers the scalability of the protocol in terms of the number of sources in the multicast groups. The proposed protocol designates a set of sources as the core sources. Each core source is a root of each tree that reaches all the destinations of the multicast group. The union of these trees constitutes the data delivery mesh, and each of the non-core sources finds the nearest core source in order to delegate its data delivery. For the efficient operation of the proposed protocol, it is important to have an appropriate number of core sources. Having too many of the core sources incurs excessive control and data packet overhead, whereas having too little of them results in a vulnerable and overloaded data delivery mesh. The data delivery mesh is optimally reconfigured through the periodic control message flooding from the core sources, whereas the connectivity of the mesh is maintained by a persistent local mesh recovery mechanism. The simulation results show that the proposed protocol achieves an efficient multicast communication with high data delivery ratio and low communication overhead compared with the other existing multicast routing protocols when there are multiple sources in the multicast group.

• Proceedings of the Korean Information Science Society Conference
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• 2002.04a
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• pp.265-267
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• 2002

인터넷에서 멀티미디어 응용들이 증가함에 따라 서비스 품질(QoS: Quality of Service)을 보장해 줄 수 있는 여러 가지 방안이 제안되어 왔는데, 일반적으로 이들 방안은 확장성과 종단간 QoS 보장 간에 상호 모순이 발생하는 경향을 가지고 있다. 본 논문에서는 이와 같은 상호 모순을 피할 수 있는 QoS 지원 방안으로서 DQSP(Dynamic QoS Support Protocol)를 제안한다. DQSP는 도메인 내에서의 자원 예약과 연결 수락 제어 메커니즘을 정의한다. DQSP는 링크 자원을 각 에지 라우터로부터의 트래픽 클래스별로 동적으로 할당하고 에지 라이투가 자신에게 할당된 링크 자원에 관한 정보를 유지하도록 한다. DQSP는 목적지로의 연결 수락 제어를 위한 QoS 신호 프로토콜이 필요 없이 에지 라우터에서 매 사용자 플로우별로 직접적으로 연결 수락 결정을 내리므로 확장성 문제 및 코어 라우터의 복잡한 기능 요구 사항 문제를 해결한다. 또한 UQSP는 에지 라우터가 트래픽 부하에 따라 자신에게 할당되어 있는 자원을 반납하거나 추가적인 자원을 제공받을 수 있도록 해 자원 오버 프로비져닝으로 인해 발생할 수 있는 비효율적인 자원 활용 문제를 해결한다. 또한 DQSP는 경로 재계산을 수행하여 라우팅을 조정해 나감으로써 효율적일 네트워크 자원 활용이 가능하다. 시뮬레이션을 통하여 DQSP와 기존의 자원 할당 및 공유 방식들을 비교한 결과 DQSP가 시그널링과 상태 정보 유지를 위한 오버헤드 면에서 기존의 종단간 QoS 보장을 제공하는 구조인 IntServ에서와 같은 확장성 문제를 발생시키지 않으면서도 효율적으로 네트워크 자원을 활용할 수 있음을 확인할 수 있었다.재 상용화 되어있는 Bellcore 의 S/KEY 시스템과의 비교를 수행하였다. 분석에서는 제품의 효율성뿐만 아니라 보안성을 중요하게 생각하였으며, 앞으로 보안 관련 소프트웨어 개발에 사용될 수 있는 도구들이 가이드 라인에 대한 정보를 제공한다.용할 수 있는지 세부 설계를 제시한다.다.으로서 hemicellulose구조가 polyuronic acid의 형태인 것으로 사료된다. 추출획분의 구성단당은 여러 곡물연구의 보고와 유사하게 glucose, arabinose, xylose 함량이 대체로 높게 나타났다. 점미가 수가용성분에서 goucose대비 용출함량이 고르게 나타나는 경향을 보였고 흑미는 알칼리가용분에서 glucose가 상당량(0.68%) 포함되고 있음을 보여주었고 arabinose(0.68%), xylose(0.05%)도 다른 종류에 비해서 다량 함유한 것으로 나타났다. 흑미는 총식이섬유 함량이 높고 pectic substances, hemicellulose, uronic acid 함량이 높아서 콜레스테롤 저하 등의 효과가 기대되며 고섬유식품으로서 조리 특성 연구가 필요한 것으로 사료된다.리하였다. 얻어진 소견(所見)은 다음과 같았다. 1. 모년령(母年齡), 임신회수(姙娠回數), 임신기간(姙娠其間), 출산시체중등(出産時體重等)의 제요인(諸要因)은 주산기사망(周産基死亡)에 대(對)하여 통계적(統計的)으로 유의(有意)한 영향을 미치고 있어 $25{\sim}29$세(歲)의 연령군에서, 2번째 임신과 2번째의 출산에서 그리고 만삭의 임신 기간에, 출산시체중(出産時體重) $3.50{\sim}3.99kg$사이의 아이에서 그 주산기사망률(周産基死亡率)이 각각

• Journal of KIISE:Computing Practices and Letters
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• v.16 no.4
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• pp.421-426
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• 2010

Due to the ease of deployment and the extended coverage, wireless mesh networks (WMNs) are gaining popularity and research focus. For example, the routing protocols that enhance the throughput on the WMNs and the link quality measurement schemes are among the popular research topics. However, most of these works assume that the locations of the mesh routers are predetermined. Since the operators in an Indoor mesh network can determine the locations of the mesh routers by themselves, it is essential to the WMN performance for the mesh routers to be initially placed by considering the performance issues. In this paper, we propose a mesh router placement scheme based on genetic algorithms by considering the characteristics of WMNs such as interference and topology. There have been many related works that solve similar problems such as base station placement in cellular networks and gateway node selection in WMNs. However, none of them actually considers the interference to the mesh clients from non-associated mesh routers in determining the locations of the mesh routers. By simulations, we show that the proposed scheme improves the performance by 30-40% compared to the random selection scheme.

• Journal of the Korean Institute of Intelligent Systems
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• v.23 no.6
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• pp.558-564
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• 2013

Wireless sensor networks (WSNs) contain limited energy resources and are left in open environments. Since these sensor nodes are self-operated, attacks such as sinkhole attacks are possible as they can be compromised by an adversary. The sinkhole attack may cause to change initially constructed routing paths, and capture of significant information at the compromised node. A localized encryption and authentication protocol (LEAP) has been proposed to authenticate packets and node states by using four types of keys against the sinkhole attack. Even though this novel approach can securely transmits the packets to a base station, the packets are forwarded along the constructed paths without checking the next hop node states. In this paper, we propose the next hop node selection method to cater this problem. Our proposed method evaluates the next hop node considering three factors (i.e., remaining energy level, number of shared keys, and number of filtered false packets). When the suitability criterion for next hop node selection is satisfied against a fix threshold value, the packet is forwarded to the next hop node. We aim to enhance energy efficiency and a detour of attacked areas to be effectively selected Experimental results demonstrate validity of the proposed method with up to 6% energy saving against the sinkhole attack as compared to the LEAP.

• KIPS Transactions on Computer and Communication Systems
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• v.6 no.1
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• pp.1-8
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• 2017

Communications for mobile sink groups such as rescue teams or platoons bring about a new challenging issue for handling mobility in wireless sensor networks. To do this, many studies have been proposed to support mobile sink groups. When closely looking at mobile sink groups, they can be divided into (multiple) small groups according to the property of applications. For example, a platoon can be divided into multiple squads to carry out its mission in the battle field. However, the previous studies cannot efficiently support the division of mobile sink groups because they do not address three challenging issues engendered by the mobile sink group division. The first issue is to select a leader sink for a new small mobile sink group. The efficient data delivery from a source to small mobile sink groups is the second issue. Last, the third issue is to share data between leader sinks of small mobile sink groups. Thus, this paper proposes a routing protocol to efficiently support the division of mobile sink groups by solving the three challenging issues. For the first issue, the proposed protocol selects a leader sink of a new small mobile sink group which provide a minimum summation of the distance between the new leader sink and the previous leader sink and the distance from the new leader sink to all of its member sinks. For the efficient data delivery from a source to small mobile sink groups in the second issue, the proposed protocol determines the path to minimize the data dissemination distance from source to small mobile sink group by calculating with the location information of both the source and the leader sinks. With regard to the third issue, the proposed protocol exploits member sinks located among leader sinks to provide efficient data sharing among leaders sinks by considering the location information of member sinks. Simulation results verified that the proposed protocol is superior to the previous protocol in terms of the energy consumption.

• The KIPS Transactions:PartC
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• v.16C no.6
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• pp.783-790
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• 2009

The necessity of wireless sensor networks is increasing in the recent years. So many researches are studied in wireless sensor networks. The clustering algorithm provides an effective way to prolong the lifetime of the wireless sensor networks. The one-hop routing of LEACH algorithm is an inefficient way in the energy consumption of cluster-head, because it transmits a data to the BS(Base Station) with one-hop. On the other hand, other clustering algorithms transmit data to the BS with multi-hop, because the multi-hop transmission is an effective way. But the multi-hop routing of other clustering algorithms which transmits data to BS with multi-hop have a data bottleneck state problem. The unequal clustering algorithm solved a data bottleneck state problem by increasing the routing path. Most of the unequal clustering algorithms partition the nodes into clusters of unequal size, and clusters closer to the BS have small-size the those farther away from the BS. However, the energy consumption of cluster-head in unequal clustering algorithm is more increased than other clustering algorithms. In the thesis, I propose an energy efficient unequal clustering algorithm which decreases the energy consumption of cluster-head and solves the data bottleneck state problem. The basic idea is divided a three part. First of all I provide that the election of appropriate cluster-head. Next, I offer that the decision of cluster-size which consider the distance from the BS, the energy state of node and the number of neighborhood node. Finally, I provide that the election of assistant node which the transmit function substituted for cluster-head. As a result, the energy consumption of cluster-head is minimized, and the energy consumption of total network is minimized.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.8 no.4
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• pp.53-64
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• 2009

Inter-vehicular communication that propagates information without infrastructures has drawn a lot of interest. However, it is difficult to apply conventional ad-hoc routing protocols directly in inter-vehicular communication due to frequent changes in the network topology caused by high mobility of the vehicles. MMFP(Multi-hop MAC Forwarding) is a unicast forwarding protocol that transport packets based on the reachability information instead of path selection or position information. However, delivering public safety messages informing road conditions such as collision, obstacles and fog through inter-vehicular communication requires broadcast rather than unicast since these messages contain information valuable to most drivers within a close proximity. Flooding is one of the simplest methods for multi-hop broadcast, but it suffers from reduced packet delivery-ratio and high transmission delay due to an excessive number of duplicated packets. This paper presents two multi-hop broadcast protocols for inter-vehicular communication that extend the MMFP. UMHB(Unreliable Multi-Hop Broadcast) mitigates the duplicated packets of MMFP by limiting the number of nodes to rebroadcast packets. UMHB, however, still suffers from low delivery ratio. RMHB(Reliable Multi-Hop Broadcast) uses acknowledgement and retransmission in order to improve the reliability of UMHB at the cost of increase in transmission delay, which we show through simulation is within an acceptable range for collision avoidance application.

• Management & Information Systems Review
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• v.28 no.1
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• pp.1-24
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• 2009

Electronic commerce markets have been increasing rapidly, which has resulted in parallel growth in the door-to-door delivery service industry. The door-to-door delivery service industry is projected to be more competitive, due to the large amount of companies that are already established and the fact that several leading multinational logistics companies are rushing into the domestic market. This is a critical period for the companies which are attempting to obtain a competitive advantage. Previous research on door-to-door delivery services has been undertaken, in relation to strategic exploration, political proposals, and user satisfaction. However, there is a lack of practical studies focused on the information systems of door-to-door service companies and its decisive roles have been undertaken. This study aims to investigate, compare, and analyze the information systems of door-to-door delivery service companies. Also, the study proposes developmental direction of how the information systems should be improved. In order to accomplish the purpose of this study, first, we examined previous research on door-to-door delivery services and their information systems. Second, we investigated and analyzed the information systems of four leading domestic companies by conducting interviews. Third, we compared and identified factors of the information systems that could be improved. Finally, we proposed its developmental direction. As a result of the study, the information systems of door-to-door delivery service companies required to provide classified services using diverse tools and develop the optimized routing model to reduce logistics costs.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2003.05a
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• pp.21-27
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• 2003

분산컴퓨팅, 다자간 협업, 대용량 고품질의 컨텐츠 교환을 지원하는 P2P는 차세대 인터넷의 핵심 어플리케이션이 될 것이다. 본래 인터넷의 근본이었던 IP 라우팅도 P2P 방식이었다. 장비가 다양해지고, PC가 증가하게 됨에 따라 동적 IP를 사용하거나, 하나의 IP를 여러 사람이 공유하여 사용하는 복잡한 방식을 취하기 시작했다. 그러나 새로운 IP 주소들이 충분히 공급될 수 있다면, 하나의 장치 당 하나의 주소 체제가 다시 각광을 받게 될 것이고, 지금처럼 불규칙적인 동적 IP 주소를 활용하지 않아도 될 것이다. 그런 의미에서 IPv6는 풍부한 주소자원을 각 단말에 부여할 수 있어, IPv16 기반의 P2P 구축은 P2P의 성능을 최적화하는 방법이 될 것이다. 현재 P2P는 콘텐츠 공유 및 전달, 네트워크/장치(하드디스크, CPU) 리소스 공유, 다자간 원격협업, 검색, 호스팅 및 프로젝트 관리 등 다양한 방법으로 활용되고 있다. 2000년경부터 대두되기 시작한 P2P 애플리케이션은 지난 2년 동안 급속하게 늘어났으며, 특히 인터넷 사용자들은 컨텐츠를 공유/전달할 목적으로 P2P를 많이 사용하고있다. 그러나 컨텐츠의 공유에 있어 MP3, 동영상, 이미지의 전달 및 공유에 그치고 있어, P2P를 기업 환경에서 지식공유 및 전달을 위한 시스템으로 활용하는 경우는 아직 미약하다. 그러므로 본 논문에서는 조직 내에서 정보활용 능력을 제고하기 위한 방안으로 P2P 시스템을 정보 공유 시스템으로 팔용하고, P2P의 성능을 최적화 할 수 있는 IPv6 기반의 개발 방안을 제안하고자 한다. 본 IPv6 기반의 정보 공유 P2P는 IPv6 전문가 그룹을 통해 시범적으로 적응하는 것으로 시작해, 학교 및 연구소를 통한 정보지식 공유 그리고 기업 정보화 솔루션으로 활용 될 수 있다.을 제시한다. 이렇게 함으로써 최대한 고객 납기를 만족하도록 계획을 수립할 수 있게 된다. 본 논문에서 제시하는 계획 모델을 사용함으로써 고객 주문에 대한 대응력을 높일 수 있고, 계획의 투명성으로 인한 전체 공급망의Bullwhip effect를 감소시킬 수 있는 장점이 있다. 동시에 이것은 향후 e-Business 시스템 구축을 위한 기본 인프라 역할을 수행할 수 있게 된다. 많았고 년도에 따른 변화는 보이지 않았다. 스키손상의 발생빈도는 초기에 비하여 점차 감소하는 경향을 보였으며, 손상의 특성도 부위별, 연령별로 다양한 변화를 나타내었다.해가능성을 가진 균이 상당수 검출되므로 원료의 수송, 김치의 제조 및 유통과정에서 병원균에 대한 오염방지에 유의하여야 할 것이다. 확인할 수 있었다. 이상의 결과에 의하면 고농도의 유기물이 함유된 음식물쓰레기는 Hybrid Anaerobic Reactor (HAR)를 이용하여 HRT 30일 정도에서 충분히 직접 혐기성처리가 가능하며, 이때 발생된 $CH_{4}$를 회수하여 이용하면 대체에너지원으로 활용 가치가 높은 것으로 판단된다./207), $99.2\%$(238/240), $98.5\%$(133/135) 및 $100\%$ (313)였다. 각각 두 개의 요골동맥과 우내흉동맥에서 부분협착이나 경쟁혈류가 관찰되었다. 결론: 동맥 도관만을 이용한 Off pump CABG를 시행하여 감염의 위험성을 증가시키지 않으면서 영구적인 신경학적 합병증을 일으키지 않았고 좋은 혈관 개존율을 보여주었다. 따라서 동맥 도관을 이용한 Off pump CABG는 관상동맥의 협착의 정도에 따라 효율적으로 시행 시 좋은 임상결과를 얻을 수 있을 것으로 생각된다.였다. 그러나 심근 기능이나