• Journal of the Korea Institute of Information and Communication Engineering
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• v.20 no.5
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• pp.1013-1019
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• 2016

This paper describes a novel Context-awareness Markov Chain Prediction (CMCP) algorithm based on movement prediction using Markov chain in Delay Tolerant Network (DTN). The existing prediction models require additional information such as a node's schedule and delivery predictability. However, network reliability is lowered when additional information is unknown. To solve this problem, we propose a CMCP model based on node behaviour movement that can predict the mobility without requiring additional information such as a node's schedule or connectivity between nodes in periodic interval node behavior. The main contribution of this paper is the definition of approximate speed and direction for prediction scheme. The prediction of node movement forwarding path is made by manipulating the transition probability matrix based on Markov chain models including buffer availability and given interval time. We present simulation results indicating that such a scheme can be beneficial effects that increased the delivery ratio and decreased the transmission delay time of predicting movement path of the node in DTN.

• The Transactions of the Korea Information Processing Society
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• v.2 no.1
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• pp.81-94
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• 1995

By intergrating technologies for protable computers, radio communications, and computer networking, the Land Mobile Computer Network(LMCN) is supposed to overcome the time and space limitation of present computer communication network. However, because the MHs(mobile hosts) do move any time, the network connectivity is often changed causing temporarily duplicated lost, or out-of-sequenced message delivery as well as frequent communications for maintainning the network connectivity. Previous works solved the problems through message flooding, used also in multicasting, resulting in high communication cost(i.e., number of communication messages). In this paper, new protocols for efficient mobility management and multicasting are proposed. The protocols define location update, handover, and multicasting procedure of a MH over a hierarchical LMCN architecture. The protocol specification is presented, and it is shown that the communication cost of the new protocols is superior to the existing ones in terms of the communication cost.

• Journal of Distribution Science
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• v.5 no.1
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• pp.5-22
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• 2007

This research is focused on the effects of salesmen's service-justice and using the IT devices on customer response. Specially, I want to know for the response when our customer take the service from the salesmen. From analysis of the resulting data, using the IT devices are increased the quality of salesmen's service-justice. Salesmen's distributive-justice affects to positive the relationship quality. But procedural justice and interactional justice cannot affect to positive the relationship quality. Maybe, I think that the reason will be a feature of insurance goods. And relationship quality affect to positive the customer's response. There are limitations on generalization due to the results based on only insurance industry, but this study will be a useful exploratory step before designing a future survey.

• The Journal of the Korea Contents Association
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• v.17 no.1
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• pp.662-672
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• 2017

Recently, with the development of mobile devices and near field communication, mobile P2P networks have been actively studied to improve the limits of the existing centralized processing system. A peer has limited components such as batteries, memory and storage spaces in mobile P2P networks. The trust of a peer should be discriminated in order to share reliable contents in mobile P2P networks. In this paper, we propose a trust discrimination scheme considering limited resources in mobile P2P environments. The proposed scheme discriminates the trust of a peer by direct rating values using the rating information of the peer and indirect rating values by the other peers. The recent update time is included in the rating information. The proposed scheme reduces the redundant rating information by comparing the recent update times of the rating information. It is shown through performance evaluation that the proposed scheme reduces the number of messages and improves the accuracy of trust over the existing scheme.

• Journal of rehabilitation welfare engineering & assistive technology
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• v.5 no.1
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• pp.65-70
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• 2011

A communication is one of the most important factors for the human beings. Therefore, people who have some problems in communication need an Augmentative & Alternative Communication (AAC) intervention to live in the human societies and several AAC systems have been developed to help the people. Lately, smart-phone is widely used to people as a communication device which can connect between persons. It can provide many useful methods and Apps to the user. If the AAC system is unified to the smart-phone, it is very effective device to the people with disabled because they can reduce the excessive expense and easily accommodate themselves to the AAC system. In this paper, an AAC program which is installed in the smart-phone or tablet PC is introduced. It has basic AAC solutions and can send SMS message to other people. We expect that the developed device can help the communication of the people with disabled and solve the social isolation of the disabled person.

• Journal of the Korea Society of Computer and Information
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• v.17 no.11
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• pp.73-81
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• 2012

This paper proposes an ETWAD(Encapsulation and Tunneling Wormhole Attack Detection) design based on positional information and hop count on Ad-Hoc Network. The ETWAD technique is designed for generating GAK(Group Authentication Key) to ascertain the node ID and group key within Ad-hoc Network and authenticating a member of Ad-hoc Network by appending it to RREQ and RREP. In addition, A GeoWAD algorithm detecting Encapsulation and Tunneling Wormhole Attack by using a hop count about the number of Hops within RREP message and a critical value about the distance between a source node S and a destination node D is also presented in ETWAD technique. Therefore, as this paper is estimated as the average probability of Wormhole Attack detection 91%and average FPR 4.4%, it improves the reliability and probability of Wormhole Attack Detection.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.8
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• pp.1717-1724
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• 2012

Information of social relationship of users on online is useful information for other services such as recommend information of commercial activity. So, there is a lot of studies analysis with connection to visualization of social network. Most of the previous works of visualization focus on representing user's relationship on social network by a complex multi dimension graph. However, this method is difficult to identify the important of relationship to focus on personal user intuitively. In order to resolve above problem, this paper proposes a new visualization method using the user's correlation and user relationship of network node. The proposed method visualizes the hierarchy relationship of users using the internal relation of network reflecting user's message and external relation of network nodes.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.21 no.1
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• pp.193-198
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• 2017

Recently, as interest in health increases, various wearable devices such as smart watch and smart band which can measure user's biometric information are being studied. Conventional wearable devices service the measured biometric information in a form that provides simple monitoring, disease prevention, and exercise amount. However, the user is Lack to deal with the dangerous situation. In this paper, we propose a hazard notification system to address these problems. The biometric information measured by the acceleration sensor and the heart rate sensor is transmitted to the application through the Arduino in real time. It identifies the risk situation through sensor priority measurement and risk situation identification algorithm. If a dangerous situation occurs, a notification message is sent to the guardian indicating the current location of the user. Therefore, it can be expected that if a dangerous situation occurs to a user who needs protection, he can respond promptly.

• Journal of the Korea Society of Computer and Information
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• v.17 no.5
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• pp.49-57
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• 2012

In P2P streaming management, peer's churning and finding efficient topology architecture optimization algorithm that reduces streaming delay is important. This paper studies a topology optimization algorithm based on the P2P streaming using peer's link information. The proposed algorithm is based on the estimation of peer's upload bandwidth using peer's link information on mesh-network. The existing algorithm that uses the information of connected links is efficient to reduce message overload in the point of resource management. But it has a risk of making unreliable topology not considering upload bandwidth. And when some network error occurs in a server-closer-peer, it may make the topology worse. In this paper we propose an algorithm that makes up for the weak point of the existing algorithm. We compare the existing algorithm with the proposed algorithm using test data and analyze each simulation result.

• Journal of the Korea Society of Computer and Information
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• v.16 no.4
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• pp.101-110
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• 2011

A smart grid networks delivers electricity from suppliers to consumers using digital technology with two-way communications to control appliances at consumers' homes to save energy, reduce cost and increase reliability and transparency. Security is critically important for smart grid networks that are usually used for the electric power network and IT environments that are opened to attacks, such as, eavesdroping, replay attacks of abnormal messages, forgery of the messages to name a few. ZigBee has emerged as a strong contender for smart grid networks. ZigBee is used for low data rate and low power wireless network applications. To deploy smart grid networks, the collected information requires protection from an adversary over the network in many cases. The security mechanism should be provided for collecting the information over the network. However, the ZigBee protocol has some security weaknesses. In this paper, these weaknesses are discussed and a method to improve security aspect of the ZigBee protocol is presented along with a comparison of the message complexity of the proposed security protocol with that of the current ZigBee protocol.