• The KIPS Transactions:PartC
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• v.11C no.7 s.96
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• pp.889-894
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• 2004

Most ad-hoc routing protocols such as AODV(Ad Hoc On-Demand Distance Vector) and DSR(Dynamic Source Routing) do not try to search for new routes if the network topology does not change. Hence, with low node mobility, traffic may be concentrated on several nodes, which results in long end-to-end delay due to congestion at the nodes. Furthermore, since some specific nodes are continuously used for long duration, their battery power may be rapidly exhausted. Expiration of nodes causes connections traversing the nodes to be disrupted and makes many routing requests be generated at the same time. Therefore, we propose a load balancing approach called Simple Load-balancing Approach (SLA), which resolves the traffic concentration problem by allowing each node to drop RREQ (Route Request Packet) or to give up packet forwarding depending on its own traffic load. Meanwhile, mobile nodes nay deliberately give up forwarding packets to save their own energy. To make nodes volunteer in packet forwarding. we also suggest a payment scheme called Protocol-Independent Fairness Algorithm (PIEA) for packet forwarding. To evaluate the performance of SLA, we compare two cases where AODV employs SLA or not. Simulation results show that SLA can distribute traffic load well and improve performance of entire ad-hoc networks.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.9 no.4
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• pp.52-59
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• 2010

MAC frame aggregation is a method that combines multiple MPDUs (MAC protocol data units) into one PPDU (PHY protocol data units) to enhance network performance at the MAC layer. In ad hoc networks, TCP underperforms due to the congestion window overshooting problem and thus by setting CWL (congestion window limit) TCP performance can be improved. In this paper, we investigate the problem of setting CWL for TCP performance optimization in ad hoc networks with MAC frame aggregation.

• 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 KIPS Transactions:PartC
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• v.13C no.4 s.107
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• pp.447-454
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• 2006

An ad-hoc network routing protocol, AODV(Ad-hoc On-demand Distance Vector) initially uses ERS(Expanding Ring Search) algorithm to control the RREQ(Route Request) retransmission in the route discovery process. Because ERS uses the fixed NTT(Node Travesal Time), it does not reflect accurately ad-hoc network environment. In this paper, we propose an improved ERS algorithm which lowers the retransmission rate. It uses RREP(Route Reply) and gives different weights in NTT of each node in accordance with the adjacency to an originating node. To show the effectiveness of the proposed algorithm, we perform a simulation using ns2. The simulation results showed that the proposed algorithm has better performance than existing algorithms.

• Journal of KIISE:Information Networking
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• v.33 no.6
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• pp.461-472
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• 2006

In this paper, we propose a novel on-demand multicasting algorithm, 'Durable Distance Vector Multicasting(DDVM),' for Mobile Ad hoc Network(MANET). DDVM has a more efficient routing-control complexity than Link State Routing(LSR) and with the smaller complexity, DDVM provides a high delivery ratio for MANET with high mobility by adapting to dynamic topological changes. This is achieved by adding 'combined path durability' statistic into the routing-control information of Distance Vector Routing(DVR). The routing-path duration statistic is computed in a fully distributed manlier at each node in the network based on only local information from neighbour nodes. We show by simulation studies the effectiveness of DDVM compared with On-demand Multicast Routing Protocol(ODMRP).

• Journal of Advanced Navigation Technology
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• v.11 no.1
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• pp.118-126
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• 2007

An ad hoc network is a system of wireless mobile nodes that dynamically self-organize in arbitrary and temporary network topologies allowing people and devices to internetwork without any preexisting communication infrastructure. Although ad hoc network is attractive solution, there are still some major flaws that prevent commercial growth. Security is one of these main barriers; ad hoc networks are known to be particularly vulnerable to security attack. It is difficult to establish a centralized key distribution center and a trusted certification authority to provide cryptographic keys and digital certificates to nodes. To prevent attacks in ad hoc routing protocols, many algorithms have been used. In this paper, we have depicted a secure framework for multipath routing in wireless multihop network, which is comprehensive solution for secure data forwarding in wireless multihop networks. With the simulation results, the proposed scheme is compared with existing source routing scheme.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2008.05a
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• pp.271-276
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• 2008

The intrusion detection system is one of the active fields of research in wireless networks. Intrusion detection in wireless mobile Ad hoc network is challenging because the network topologies is dynamic, lack centralization and are vulnerable to attacks. This paper is about the effective enhancement of the IDS technique that is being implemented in the mobile ad hoc network and deals with security and vulnerabilities issues which results in the better performance and detection of the intrusion.

• Review of KIISC
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• v.19 no.4
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• pp.11-20
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• 2009

차량네트워크(VANET)는 이동형 에드 혹 네트워크의 가장 유망한 응용환경으로 인식되어 지고 있다. 특히, 차량간의 안전주행 통신인 V2V의 경우 운전자의 안전을 위한 통신기술로 주목받고 있다. 안전주행을 위해서 V2V에서 송수신되는 메시지는 다양한 네트워크 공격을 막기 위해서 반드시 인증이 되어야 하는 반면 운전자의 위치 프라이버시를 보호하기 위해서는 익명성이 보장되어야 한다. 이러한 보안 속성은 V2V 통신만의 고유한 성질로써, 현재 인증과 프라이버시를 동시에 보장하기 위한 인증기술에 대한 연구가 활발히 진행되고 있다. 본 고에서는 프라이버시를 보장하는 V2V 인증 프로트콜들을 분석하고 보안 및 효율성 관점에서 각 프로트콜을 비교분석한다.

• Proceedings of the Korean Information Science Society Conference
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• 2004.04a
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• pp.517-519
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• 2004

Chord(6)는 N개의 노드로 이루어진 P2P(Peer-to-Peer)네트워크에서 검색에 사용되는 메시지를 O(logN)으로 줄인 P2P 검색 알고리즘이다. 하지만 모바일 Ad-hoc 네트워크에 이를 적용할 경우 검색 성공률이 매우 떨어져 (1000개의 노드가 도보속도(2m/s)로 움직이는 경우： 검색 성공률 30%이하)P2P 검색이 거의 이루어지지 않는 문제점이 발생한다. 본 논문에서는 이 같은 문제점을 극복하기 위한 알고리즘인 Backtracking Chord을 제안한다. Backtracking Chord 방식은 O(logN)메시지를 사용하여 순차적으로 t번까지 검색을 요청함으로써(t： Timeout의 횟수(0 < t< logN)) t에 따라 최고 88%(t>4)까지 검색 성공률을 높일 수 있다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2007.06a
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• pp.73-75
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• 2007

The Ad Hoc Network Interfaces has been tremendously useful in doing capacity planning and performance prediction. However, in many real-world cases. it has found that the predicted results form a queuing analysis differ substantially from the actual observed performance. Specially, in recent years, a number of studies have demonstrated that for some environments, the traffic pattern is self-similar rather than Poisson. In this paper, we study these Clustering characteristics and the definition of standadization processes.