• Journal of KIISE:Information Networking
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• v.32 no.1
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• pp.51-59
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• 2005

In this paper, we propose and implement a hybrid-type video conference system using SIP protocol proposed in IEFT. This conference system, all signaling is controled by the server, while the media communication can be managed either by UAs or by the server. as a result, the complexity of its routing and user state management is reduced and it is applicable to the mobile environment of the ad-hoc models. The implemented server is scale enough to be used in a large conference because it only takes charge of signaling part. And also we see that UAs are only suitable in the small conference where less than ten people can join.

• The Journal of the Korea institute of electronic communication sciences
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• v.4 no.1
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• pp.14-19
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• 2009

In Mobile Ad-hoc Network, link failure and packet loss may occur frequently due to its nature of mobility and limited battery life. In this paper, an enhanced robust routing protocol based on AODV(Ad hoc On-demand Distance Vector routing) by monitoring variation of receiving signal strength is proposed. New metric function that consists of node mobility and hops of path is used for routing decision. For preventing route failure by node movement during data transmission, a new route maintenance is presented. If the node movement is detected, the routing agent switches local path to its neighbor node. Simulation results show that the performance of the proposed routing scheme is superior to previous AODV protocol.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.4
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• pp.1041-1047
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• 2010

One of the weaknesses of ad hoc network is that a route used between a source and a destination is to break during communication. To solve this problem, one approach consists of selecting routes whose nodes have the most stable link cost. In this paper proposes a new method for improving the low power distributed MAC. The method is rule-based on the context awareness of the each nodes energy in clustering. The proposed networks scheme could get better improve the awareness for data to achieve and performance on their clustering establishment and messages transmission.

• Annual Conference of KIPS
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• 2002.11b
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• pp.1261-1264
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• 2002

Ad-hoc 무선망은 각자의 이동 노드에 대한 제약이 없고, 유선망이나 기지국과 같은 기반구조를 필요로 하지 않기 때문에 병원, 전시장, 생산 현장과 같은 곳에서 사용되는 자치분산 네트워크이다. 최근 들어 이동 Ad-hoc 네트워크에서 사용되는 AODV, DSR, TORA, ZRP등의 라우팅 프로토콜 연구가 활발히 이루어지고 있는 실정이다. 따라서 본 논문에서는 AODV 라우팅 프로토콜을 사용하여 다양한 네트워크 환경에서 성능평가와 라우팅 프로토콜의 문제점을 수정, 개선하였다.

• The KIPS Transactions:PartC
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• v.13C no.4 s.107
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• pp.455-460
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• 2006

Currently, the IETF group is working on service differentiation in the Internet. However, in wireless environments such as Ad-hoc networks, where channel conditions are variable and bandwidth is scarce, the Internet differentiated services are suboptimal without lower layers' support. The IEEE 802.11 standard for Wireless LANs is the most widely used WLAN standard today. 1t has a mode of operation that can be used to provide service differentiation, but it has been shown to perform badly. In this paper, we present a new service differentiation scheme for support QoS in the wireless IEEE 802.11, which is based on a multiple queuing system to provide priority of user's flow. We simulate and analyze the performance of our algorithm and compare its performance with the original IEEE 802.11b protocol. Simulation results show that our approach increases overall throughput in the MAC layer.

• Journal of Information Processing Systems
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• v.13 no.6
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• pp.1436-1458
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• 2017

Quorum-based algorithms are widely used for solving several problems in mobile ad hoc networks (MANET) and wireless sensor networks (WSN). Several quorum-based protocols are proposed for multi-hop ad hoc networks that each one has its pros and cons. Quorum-based protocol (QEC or QPS) is the first study in the asynchronous sleep scheduling protocols. At the time, most of the proposed protocols were non-adaptive ones. But nowadays, adaptive quorum-based protocols have gained increasing attention, because we need protocols which can change their quorum size adaptively with network conditions. In this paper, we first introduce the most popular quorum systems and explain quorum system properties and its performance criteria. Then, we present a comparative and comprehensive survey of the non-adaptive and adaptive quorum-based protocols which are subsequently discussed in depth. We also present the comparison of different quorum systems in terms of the expected quorum overlap size (EQOS) and active ratio. Finally, we summarize the pros and cons of current adaptive and non-adaptive quorum-based protocols.

• Proceedings of the Korean Information Science Society Conference
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• 2004.04a
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• pp.502-504
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• 2004

이동성이 중요시되는 네트워크에서 특정 프로토콜의 성능 평가를 위해서는 노드의 이동패턴을 정확하게 표현할 수 있는 Mobility Model이 필요하다. 노드의 연속적인 이동패턴을 필요로 하는 Mobile Ad-hoc 네트워크를 위해선 Markov process 기반의 Gauss-Markov Mobility Model이 적절하다. 그러나 맵의 엣지 부근에서 노드 이동의 부적절한 처리로 인해, 기존의 Gauss-Markov Model은 편중된 이동 패턴을 야기한다. 본 논문은 엣지 부근의 평균 이동각도를 랜덤하게 조정함으로써 기존의 모델이 가진 문제를 해결하고, 시뮬레이션을 통해서 이를 검증한다.

• The KIPS Transactions:PartC
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• v.12C no.6 s.102
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• pp.809-816
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• 2005

MANET(mobile ad hoc network) cn be one of the access networks of BcN(broadband convergence network), and an user node requires address auto-configuration protocol for mu14i-hop environment. Some address auto-configuration protocols are proposed for independent MANET, but they don't consider BcN-accessable MANET environment. In this paper, new address auto-configuration protocol for wireless nodes is proposed. With this proposal, they ran configure their global addresses automatically in hybrid MANETs as BcN access networks. The autoconfiguration protocol modifies IPv6 NDP(neighbor discovery protocol) messages to deliver global prefix information to all wireless nodes, and avoids message boradcasting to minimize network overhead.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2008.10a
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• pp.494-497
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• 2008

In Mobile ad hoc networks (MANET), nodes could transmit packets for each other to communicate beyond their transmission range without centralized control. Unlike infrastructure-based wireless networks, due to the unique characteristics of MANETs such as open network architecture, stringent resource constraints and highly dynamic network topology, networks are vulnerable to wormhole attacks launched through colluding nodes. In this paper, we develop an wormhole detection and prevention algorithm for MANET.

• Information and Communications Magazine
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• v.24 no.7
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• pp.79-88
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• 2007

본고에서는 현재 일반적으로 가장 널리 사용되고 있는 네트워크 시뮬레이터인 NS-2(Network Simulator-2)에 대하여 알아본다. NS-2는 네트워킹의 성능분석을 목적으로 개발된 이벤트 기반(event-driven)의 시뮬레이터이다. 이 시뮬레이터의 적용 범위는 유선 네트워크의 경우 TCP/IP 프로토콜 패밀리와 각종 라우팅 프로토콜에 대한 시뮬레이션이 가능하며, 무선 네트워크에 경우에는 Ad Hoc 네트워크, WLAN, Mobile-IP와 Cellular network 등의 시뮬레이션이 가능하다. GUI가 부족하고 사용이 어렵다는 단점에도 불구하고, 공개된 소스와 두터운 이용자층에 힘입어 널리 사용되는 NS-2의 개요 및 시뮬레이션 방법에 대해 알아보기로 한다.