• Proceedings of the IEEK Conference
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• 2004.06a
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• pp.241-244
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• 2004

In recent years, WDM networks have received much attention as the Internet backbone networks because of the explosive growth of the Internet IP-based traffic. The Optical Burst Switching (OBS) has been proposed as an effective optical switching technology in the WDM networks. OBS has the advantages in 1) the high usage rate of the bandwidth, and 2) no necessity of optical buffer. However OBS has the burst-contention problem in the networks. The deflection routing is proposed as one of means to solve this problem. In this paper, we propose a new routing method of using deflection routing. In addition. we propose a QoS/CoS control method using a new routing algorithm. Finally, we show the variety of the proposed methods by computer simulations.

• Journal of Contemporary Eastern Asia
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• v.12 no.2
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• pp.89-97
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• 2013

This paper explores the influences of the traditional Chinese culture on social relations in China. It provides an introduction to the concept of Guanxi, the notion that social connections are based on socially situated reciprocity. This is different from social interaction in Western society that is based on self-interest and equity. Guanxi represents the foundation of social networks in many Eastern countries. As such, the study of social networks in China requires scholars to examine Guanxi networks. The paper demonstrates how a Guanxi perspective might be added to the examination of various theories that comprise structural (network) theory, including social capital theory, social exchange theory, cognitive and contagion theories, and the role of homophily for the study of Chinese society and its social organizations.

• Journal of information and communication convergence engineering
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• v.14 no.2
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• pp.84-88
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• 2016

As good example of potential application-specific requirement, (m,k)-firm real-time streams have been recently introduced to deliver multimedia data efficiently in wireless sensor networks. In addition to stream model, communication protocols to meet specific (m,k)-firm real-time streams have been newly developed or extended from existing protocols. However, since the existing schemes for an (m,k)-firm stream have been proposed under typical flat architecture, the scalability problem remains unsolved when the number of real-time flows increases in the networks. To solve this problem, in this paper, we propose a new clustering scheme for an (m,k)-firm stream. The two different clustering algorithms are performed according to either the (m,k)-firm requirement or the deadline. Simulation results are presented to demonstrate the suitability of the proposed scheme under hierarchical architecture by showing that its performance is acceptable irrespective of the increase in the number of flows.

• Journal of Communications and Networks
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• v.8 no.4
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• pp.461-474
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• 2006

A group key exchange protocol is a cryptographic primitive that describes how a group of parties communicating over a public network can come up with a common secret key. Due to its significance both in network security and cryptography, the design of secure and efficient group key exchange protocols has attracted many researchers' attention over the years. However, despite all the efforts undertaken, there seems to have been no previous systematic look at the growing problem of key exchange over combined wired and wireless networks which consist of both stationary computers with sufficient computational capabilities and mobile devices with relatively restricted computing resources. In this paper, we present the first group key exchange protocol that is specifically designed to be well suited for this rapidly expanding network environment. Our construction meets simplicity, efficiency, and strong notions of security.

• Journal of Advanced Marine Engineering and Technology
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• v.41 no.2
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• pp.156-162
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• 2017

This paper investigates two-hop extension communication in wireless body area networks. Many previous studies have demonstrated that two-hop extended topology outperforms single-hop topology. Although many researchers have proposed using two-hop extension communication to improve link reliability, no one has considered using a relay selection algorithm or provided a suitable solution for wireless body area networks. The design goal of the proposed algorithm is selecting a proper relay node to retransmit failed packets distributively. The proposed algorithm configures the carrier sensing period to choose one relay node promptly without requiring additional interaction. We analyze the link conditions corresponding to various body postures and investigate which factors are proper to determine the carrier sensing period. The empirical results show that the proposed algorithm reduces the expected number of transmissions required to deliver a packet successfully.

• Proceedings of the KIEE Conference
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• 2007.04a
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• pp.433-435
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• 2007

Geographic wireless sensor networks use position information for Greedy routing. Greedy routing works well in dense network where as in sparse network it may fail and require the use of recovery algorithms. Recovery algorithms help the packet to get out of the communication void. However, these algorithms are generally costlier for resource constrained position based wireless sensor type networks. In the present work, we propose a Void Avoidance Algorithm (VAA); a novel idea based on virtual distance upgrading that allows wireless sensor nodes to remove all stuck nodes by transforming the routing graph and forward packet using greedy routing only without recovery algorithm. In VAA, the stuck node upgrades distance unless it finds next hop node which is closer to the destination than itself. VAA guarantees the packet delivery if there is a topologically valid path exists. NS-2 is used to evaluate the performance and correctness of VAA and compared the performance with GPSR. Simulation results show that our proposed algorithm achieves higher delivery ratio, lower energy consumption and efficient path.

• Journal of Korea Multimedia Society
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• v.9 no.6
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• pp.735-741
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• 2006

In the near future, the wireless home networks will connect several devices at home. Due to the broadcast nature of a wireless network, anyone can hear and capture communication. Thus, we need to protect our network from attacks outside the house. In this paper, we propose and implement a security system that provides different levels of the security services to heterogenous home devices. To reduce the communication cost and workload of the server, home devices send the encrypted messages directly instead of sending through the sever. We implement our security system on laptops using JAVA and our security system achieves the better performance with the large number of devices and messages in a network. In order to prove that our security system is secure against various attacks, we analyze the security of our security system using attack trees.

• Journal of information and communication convergence engineering
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• v.7 no.3
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• pp.241-246
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• 2009

Advances in mobile and wireless networking technologies have enabled mobile ad hoc networks applicable to a wide range of areas. Many cases of even such ad hoc networks demand to be accessible to the global network. Owing to be diversified in features depending on applications, however, some those networks may consist of devices or nodes which do not facilitate all the same transport protocols. This results in unreachable situations of establishing ad hoc network: such as non-existence of all required access points, faults or contention in a path of particular protocol communication. Interworking between different transport protocols can alleviate such problems. This paper proposes an interworking scheme to improve data transport performance and network accessibility, especially in such a mobile ad hoc network that is applicable to data communications among ships or user's convenient u-health services. Modeling and simulation analysis are used to verify the improvement.

• Journal of Sensor Science and Technology
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• v.23 no.3
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• pp.158-164
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• 2014

In indoor sensor networks equalization algorithms based on the minimization of Euclidean distance (MED) for the distributions of constant modulus error (CME) have yielded superior performance in compensating for signal distortions induced from optical fiber links, wireless-links and for impulsive noise problems. One main drawback of MED-CME algorithms is a heavy computational burden hindering its implementation. In this paper, a recursive gradient estimation for weight updates of the MED-CME algorithm is proposed for reducing the operations $O(N^2)$ of the conventional MED-CME to O(N) at each iteration time for N data-block size. From the simulation results of the proposed recursive method producing exactly the same results as the conventional method, the proposed estimation method can be considered to be a reliable candidate for implementation of efficient receivers in indoor sensor networks.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.7C
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• pp.584-591
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• 2012

Distributing a Certificate Revocation List (CRL) quickly to all vehicles in the system requires a very large number of road side units (RSUs) to be deployed. In reality, initial deployment stage of vehicle networks would be characterized by limited infrastructure as a result in very limited vehicle to infrastructure communication. However, every vehicle wants the most recent CRLs to protect itself from malicious users and malfunctioning equipments, as well as to increase the overall security of the vehicle networks. To address this challenge, we design and implement a nomadic device based CRL acquisition method using nomadic device's communication capability with cellular networks. When a vehicle could not directly communicate with nearby RSUs, the nomadic device acts as a security mediator to perform vehicle's security functions continuously through cellular networks. Therefore, even if RSUs are not deployed or sparsely deployed, vehicle's security threats could be minimized by receiving the most recent CRLs in a reasonable time.