• Proceedings of the IEEK Conference
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• 2005.11a
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• pp.289-292
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• 2005

IEEE802.11 DCF에서는 hidden node문제를 해결하기 위하여 RTS/CTS 교환을 사용한다. 그러나 실제로는 전송에 필요한 파워보다 간섭을 일으킬 수 있는 파워가 작다. 따라서 RTS나 CTS를 받지 않은 노드에서 전송을 시작할 경우에도 간섭에 의해 충돌이 발생할 수 있다. 멀티홉 애드혹 환경에서는 이 현상이 더 큰 성능 저하를 불러 일으킬 수 있다. 본 논문에서는 기존의 RTS/CTS 교환에서 CTS를 받은 노드들이 STS 패킷을 보내고 STS를 받은 노드가 자신이 전송을 시작할 경우 데이터를 받는 노드에서의 간섭 효과를 계산해 간섭 효과가 클 경우 전송을 지연시키는 과정을 추가하였다. 따라서 간섭에 의한 충돌이 발생하지 않도록 하였다. 또한 시뮬레이션 결과를 통하여 이 방식이 멀티홉 애드혹 환경에서 성능을 향상 시켰음을 보였다.

• Journal of Advanced Marine Engineering and Technology
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• v.35 no.8
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• pp.1092-1097
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• 2011

Data communications at sea are done by the traditional radio and satellite carriers. Because of the restrictions on the data rate and cost of the carriers, a novel data communication system at sea is needed. Nowadays the efforts to make use of the broadband land carriers at sea have been pursued. This paper proposes a routing scheme (NTCR) using the various carriers on land for a MANET model at sea. The NTCR scheme optimizes the route using a chosen carrier by taking considerations of normalized transmission characteristics (NTC) of applications and carriers. The NTCR scheme is compared with the MWR (max-win based routing) scheme.

• Journal of Advanced Marine Engineering and Technology
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• v.36 no.2
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• pp.302-308
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• 2012

Self-configuration network model is to overcome the limits of data communications at sea. As a research for enhancing the connectivity and scalability of data networks at sea using the diversity and heterogeneity of the data networks on land, in this paper, a routing scheme (NLTCR) based on not conventional hop counts but distances to destination ships is introduced. The NLTCR seeks an optimal route by normalized distances to a destination, and transmission characteristics of applications and carriers. Performance is evaluated and compared with those of the max-win (MWR) and the normalized transmission characteristics (NTCR) based schemes.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.7 no.7
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• pp.1721-1736
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• 2013

Black and gray hole attack is one kind of routing disturbing attacks and can bring great damage to the network. As a result, an efficient algorithm to detect black and gray attack is important. This paper demonstrate an adaptive approach to detecting black and gray hole attacks in ad hoc network based on a cross layer design. In network layer, we proposed a path-based method to overhear the next hop's action. This scheme does not send out extra control packets and saves the system resources of the detecting node. In MAC layer, a collision rate reporting system is established to estimate dynamic detecting threshold so as to lower the false positive rate under high network overload. We choose DSR protocol to test our algorithm and ns-2 as our simulation tool. Our experiment result verifies our theory: the average detection rate is above 90% and the false positive rate is below 10%. Moreover, the adaptive threshold strategy contributes to decrease the false positive rate.

• The Journal of the Korea institute of electronic communication sciences
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• v.7 no.3
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• pp.491-497
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• 2012

Network coding is that the nodes can combine and mix the packets rather than merely forward them. Therefore, network coding is expected to improve throughput and channel efficiency in the wireless network. Relevant researches have been carried out to adapt network coding to wireless multi-hop network. In this paper, we designed the network coding for bidirectional traffic service in routing layer and IP layer of Ad-hoc network. From the simulation result, the traffic load and the end to end distance effect the performance of the network coding. As end to end distance and the traffic load become larger, the gain of network coding become more increased.

• The Journal of the Korea institute of electronic communication sciences
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• v.5 no.6
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• pp.588-594
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• 2010

In a multi-hop wireless sensor network, broadcasting is an elementary operation to support command message sending, route discovery and other application tasks. Broadcasting by flooding may cause serious redundancy, contention, and collision in the network, which is referred to as the broadcast storm problem. Many broadcasting schemes have been proposed to give better performance than simple flooding in wireless sensor network. How to decide whether re-broadcast or not also poses a dilemma between reach ability and efficiency under different host densities. In this paper, we present popular broadcasting schemes, which can reduce re-broadcast packets and improve SRB(Saved ReBroadcast). Simulation results show different levels of improvement over the simple flooding scheme.

• Journal of information and communication convergence engineering
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• v.7 no.4
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• pp.475-479
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• 2009

In ad hoc network, the scarce energy management of the mobile devices has become a critical issue in order to extend the network lifetime. Current research activity for the Minimum Energy Multicast (MEM) problem has been focused on devising efficient centralized greedy algorithms for static ad hoc networks. In this paper, we consider mobile ad hoc networks(MANETs) that could provide the reliable monitoring and control of a variety of environments for remote place. Mobility of MANET would require the topology change frequently compared with a static network. To improve the routing protocol in MANET, energy efficient routing protocol would be required as well as considering the mobility would be needed. In this paper, we propose a new method, the CACH(Context-aware Clustering Hierarchy) algorithm, a hybrid and clustering-based protocol that could analyze the link cost from a source node to a destination node. The proposed analysis could help in defining the optimum depth of hierarchy architecture CACH utilize. The proposed CACH could use localized condition to enable adaptation and robustness for dynamic network topology protocol and this provide that our hierarchy to be resilient. As a result, our simulation results would show that CACH could find energy efficient depth of hierarchy of a cluster.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.10 no.2
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• pp.77-83
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• 2010

Vehicular Ad Hoc Networks are self-organizing Peer-to-Peer networks that typically have highly mobile vehicle nodes, moving at high speeds, very short-lasting and unstable communication links. VANETs are formed without fixed infrastructure, central administration, and dedicated routing equipment, and network nodes are mobile, joining and leaving the network over time. So, VANET-security is very vulnerable for the intrusion of malicious and misbehaving nodes in the network, since VANETs are mostly open networks, allowing everyone connect, without centralized control. In this paper, we propose a rough set based anomaly detection method that efficiently identify malicious behavior of vehicle node activities in these VANETs, and the performance of a proposed scheme is evaluated by a simulation in terms of anomaly detection rate and false alarm rate for the threshold ${\epsilon}$.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.8 no.2
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• pp.9-14
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• 2008

Mobile Ad-Hoc network is the network of mobile nodes which has no fixed infrastructure, and mobile node in MANET can move freely and communicate with each other. The location management is an important issue because location information of a mobile node is frequently changed in MANET. In this paper, we propose new quorum system applying the gravity of locality of mobile nodes adaptively by using the fuzzy-logic for the mobility of mobile nodes in order to manage location information of mobile nodes in MANET efficiently. The performance of the proposed scheme is evaluated by an analytical model and compared with those of existing UQS and DQS schemes.

• The Journal of the Korea institute of electronic communication sciences
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• v.7 no.2
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• pp.257-262
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• 2012

In this paper, transmission performance for serval VoIP traffics is meaured and analysised over MANET(Mobile Ad-hoc Networks) under some types of intrusions. VoIP simulator based on NS-2 is used for performance measure. In the simulation, MOS, network delay, packet loss rate and call connection rate is measured for transmission performance. With analysis of measued data, characteristics of each traffics for transmission performance parameters is showed on MANET under multi intrusions, As a results of this paper, some recommendation condtion for codec selection and blackhole intrusion is suggested to implement VoIP services on MANET under multi intrusions like as DDoS and blockhole intrusions.