• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.4
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• pp.76-89
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• 2014

In this paper, we propose a MAC(Media Access Control) protocol based on flexible RWT(RTS Waiting Time) for underwater mobile ad-hoc networks with a three-way handshaking mechanism. This protocol can solve a problem of collision between RTS(Request-To-Send) and CTS(Clear-To-Send) packets in existing MACA(Multiple Access with Collision Avoidance) protocol. This proposed MAC protocol is also an effective protocol which can apply to underwater mobile ad-hoc networks in a real field by using implementable technologies. We set flexible RTS Waiting Time called RWT, considering various characteristics of underwater environment. It is possible to support variable network size according to node mobility. Finally, we conduct a performance evaluation between proposed MAC protocol and existing MACA based MAC protocol through practical implementation and experiment. As a result, we verify the superiority of our proposed MAC protocol in terms of throughput, packet drop rate, average transmission time, energy consumption and channel utilization.

• Journal of KIISE:Computing Practices and Letters
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• v.12 no.1
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• pp.31-42
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• 2006

Context-awareness is a technology to facilitate information acquisition and execution by supporting interoperability between users and devices based on users' context. It is one of the most important technologies in ubiquitous computing. In this paper, we propose a middleware and a context server for dealing with context-awareness in ubiquitous Computing and implement an application system using them. The middleware proposed in our work plays an important role in recognizing a moving node with mobility by using a Bluetooth wireless communication technology as well as in executing an appropriate execution module according to the context acquired from a context server. In addition, the proposed context server functions as a manager that efficiently stores into a database server context information, such as user's current status, physical environment, and resources of a computing system. Finally, our application system implemented in our work one which provides a music playing service based on context information, and it verifies the usefulness of both the middleware and the context server developed in our work.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.9 no.3
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• pp.93-99
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• 2009

The Internet Engineering Task Force (lETF)proposed the Mobile IPv6 protocol to provide host mobility in IPv6-based network and to offer a standardized technology. However, Mobile IPv6 (MIPv6) is not applied in actual network because of long handover latency and packet loss problems. Therefore, to compensate these drawbacks, many studies are in progress and FMIPv6 (Fast handover for Mobile IPv6) is one of the studies that has been proposed to supplement the shortcomings of MIPv6. But there are problems occurred in using router tunneling which causes packet loss and out of sequence problems. In this paper, we propose an Advanced Mobile IPv6 (AMIPv6) protocol to minimize the handover latency when Mobile Node frequently moves in each subnet. We compared the performance analysis of AMIPv6 handover latency with MIPv6 handover latency in the same network environment to prove that AMIPv6 is more efficient.

• The KIPS Transactions:PartC
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• v.17C no.2
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• pp.181-189
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• 2010

HAP(High Altitude Platform) is a stationary aerial platform positioned in the stratosphere between 17Km and 22Km height and it could act as an MBS (Mobile Base Station). HAP based Network has advantages of both satellite system and terrestrial communication system. In this paper we study the deploy of multiple HAP MBS that can provides efficient communication for users. For this study, EM(Expectation Maximization) clustering algorithm is used to cluster terrestrial mobile nodes. The object of this paper is improving EM algorithm into the clustering algorithm for efficiency in variety aspects considering distance between mobile terminal units and speed of mobile terminal units, and estimating performance of HAP MBS deploy technique with use of improved EM algorithm using RWP (Random Waypoint) node mobility.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.13 no.5
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• pp.17-26
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• 2013

ISO/IEC 29157 originally developed in the Republic of Korea and is based on commercially available PicoCast v1.0. ISO/IEC JTC1 SC6 was registered by the international standard on May 2010. A single platform for a variety of applications and media formats to support development objectives were. ISO/IEC 29157 based wireless networks, ie, Pico-net to master node periodically transmit sync signal is synchronized to the number of slave nodes have the communications structure. Pico-net also supports a variety of network topologies and direct communication between nodes(single-hop communication) and QoS is guaranteed. But Pico-net network structure has the following problems. Loss of communication problems due to mobile nodes, resulting in limitations of node mobility and wireless network operation range of conventional wireless networks operating range less than 1/4 was reduced to the problem. In this paper, a possible solution to the problems mentioned is proposed, using multi-hop communication technology and sync signal transmission technology between nodes.

• Journal of the Institute of Electronics and Information Engineers
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• v.49 no.9
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• pp.225-234
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• 2012

In Wireless Sensor Networks (WSNs) where deployed sensors are not stationary, the most important demand of is to design a cost effective and reliable network. This paper proposes an energy aware network construction and routing scheme, which is based on the hierarchical approach to distribute the task in some sensors in order to prolong the network lifetime. It aims to make even the energy consumption on constitute nodes. With the node hierarchy, the sink initiates the construction by electing gateway nodes in the network and the elected gateway nodes participate to form logical clusters by electing a cluster head in each cluster. Then, the cluster heads aggregate data from the sensing sensors and transmit the data to the sink through the gateway. Our simulation result illustrates that the proposed scheme provides a basement to reduce the source of energy dissipation in network construction, and as well as in data routing.

• Journal of Intelligence and Information Systems
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• v.23 no.2
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• pp.89-105
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• 2017

As the advances of technology in mobile networking and the popularity of online social networks (OSNs), the mobile social networks (MSNs) provide opportunities for marketing strategy. Therefore, understanding the information diffusion in the emerging MSNs is a critical issue. The information diffusion address a problem of how to find the proper initial nodes who can effectively propagate as widely as possible in the minimum amount of time. We propose a new diffusion scheme, called Hotspot DBC, which is to find k influential nodes considering each node's mobility behavior in the hotspot zones. Our experiments were conducted in the Opportunistic Network Environment (ONE) using real GPS trace, to show that the proposed scheme results. In addition, we demonstrate that our proposed scheme outperforms other existing algorithms.

• Journal of Internet Computing and Services
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• v.6 no.3
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• pp.85-95
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• 2005

Whereas the traditional multicast schemes based on Mobile IP can support a limited number of very large multicast groups, the Xcast protocol can support a very large number of small multicast groups, In the Xcast, the source node encodes the list of destinations in the Xcast header. Therefore, the maximum packet size in the network limits the number of destinations that a Xcast packet may have. In this paper, an enhanced Xcast protocol is proposed to solve the multicast group size limitation of the existing Xcast protocol in providing multicast service for mobile nodes. Moreover, the SIP (a very flexible control plane protocol) is integrated with the proposed multicast scheme to provide mobility awareness on the application layer. The simulation results verify that the proposed multicast scheme not only increases the packet delivery ratio and the data packet forwarding efficiency but also achieves low latency of packets in the network.

• Journal of KIISE:Information Networking
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• v.34 no.1
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• pp.48-61
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• 2007

WiBro (Wireless Broadband) service, developed in Korea, can provide the host mobility while its users hang around within the subnet. Next-generation Internet protocols, IPv6 and Mobile IPv6 (MIPv6), provide a plenty of addresses to the nodes and enable the handover between different subnets. However, MIPv6 is not enough to support a real time service such as VoIP (Voice over IP) due to the long latency, and it is necessary to develop an enhanced handover mechanism which is optimized to the WiBro networks. In this paper, we suggest an improved fast handover mechanism while the mobile node moves around WiBro networks. The proposal is based on Fast Mobile IPv6 (FMIPv6) which is the representative protocol for fast handover, and reduces the handover latency by the close interaction between the link layer (WiBro MAC) and IP layer (FMIPv6). Finally, we analyze the performance of proposed mechanism through the mathematical analysis.

• Journal of KIISE:Information Networking
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• v.31 no.5
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• pp.429-437
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• 2004

The mobileip working group is equipped with the RR(Return Routabilit) taking the simple procedures and small amount of cryptographic operations by considering the processing capability of the mobile node however it dose not provide security features enough. To replace with enhanced methods, mobileip WG is making an effort to find the approved solutions include CGA(Craptographically Generated Address), IPsec(Internet Protocol Security) as well as the existing infrastructure such as AAA(Authentication, Authorization and Account) and PKI(Public Key Infrastructure). In this paper, we propose the authentication and route optimization based on AAA suitable for the requested security service for its successful story in wireless network such as 802.11 and 3GPP(3rd Generation Partnership Project) as well as wired one. We analyze the effectiveness of our scheme according to the traffic and mobility properties. The result shows the cost reduction up to 20 percent comparing with RR.