• Journal of Digital Convergence
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• v.11 no.7
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• pp.215-223
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• 2013

As cloud computing is activated, a variety of cloud services are being distributed. However, to use each different cloud service, you must perform a individual user authentication process to service. Therefore, not only the procedure is cumbersome but also due to repeated authentication process performance, it can cause password exposure or database overload that needs to have user's authentication information each cloud server. Moreover, there is high probability of security problem that being occurred by phishing attacks that result from different authentication schemes and input scheme for each service. Thus, when you want to use a variety of cloud service, we proposed OpenID based user authentication scheme that can be applied to a multi-cloud environment by the trusted user's verify ID provider.

• Proceedings of the IEEK Conference
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• 2008.06a
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• pp.703-704
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• 2008

Multi-agent technologies are essential in realizing the upcoming ubiquitous environment. In the multi-agent environment, each agent has its own set of services and stores these services in the service repository of the multi-agent system. By using this repository, the user can retrieve the most appropriate service. In this paper, we propose an efficient service repository architecture that can improve the existing agent-based service discovery.

• Journal of Intelligence and Information Systems
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• v.11 no.3
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• pp.1-23
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• 2005

Personalized reminder systems have to identify the user's current needs dynamically and proactively based on the user's current context. However, need identification methodologies and their feasible architectures for personalized reminder systems have been so far rare. Hence, this paper aims to propose a proactive need awaring mechanism by applying agent, semantic web technologies and RFID-based context subsystem for a personalized reminder system which is one of the supporting systems for a robust ubiquitous service support environment. RescorlaWagner model is adopted as an underlying need awaring theory. We have created a prototype system called NAMA(Need Aware Multi-Agent)-RFID, to demonstrate the feasibility of the methodology and of the mobile settings framework that we propose in this paper. NAMA considers the context, user profile with preferences, and information about currently available services, to discover the user's current needs and then link the user to a set of services, which are implemented as web services. Moreover, to test if the proposed system works in terms of scalability, a simulation was performed and the results are described.

• Journal of Broadcast Engineering
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• v.14 no.2
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• pp.178-188
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• 2009

In this paper, we propose the method which provides efficient sub-channel allocation for handoff and new call supporting multi-media service in AMC-based OFDMA system. Firstly, we apply the multi-band method which provides different AMC method according to the location of user terminals. Also, in OFDMA system environment that a base station has a lot of sub-channels, we adopt the sub-channel allocation scheme that provides a higher priority to handoff call and real-time service about handoff and new calls with multi-meida service. The simulation results show that the proposed scheme plays a role in increasing the number of new and handoff calls meeting the required blocking rate.

• Journal of Korea Society of Digital Industry and Information Management
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• v.10 no.1
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• pp.47-53
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• 2014

LTE-Advanced is the evolved version of LTE which is currently in progress at the 3GPP. At present, as the number of smart phone users is rapidly increasing, the demand for ever more capacity is driven largely by video usage and high quality data communication and so on, this let more researchers study about LTE-A all over the world. LTE-A aims to achieve improved service and communication quality over 3G system at the aspect of throughput, peak data rate, latency, and spectral efficiency. Among various features in LTE-A, the multi-user MIMO(MU-MIMO), in which the base station transmits several streams to multiple receivers, has expected to give better quality for system. In this paper, we investigate performances of various types of downlink receivers with fixed number of antennas. we first review the development process from LTE to LTE-A. Second we introduce TM9 which is adopted in Rel.10 for MU-MIMO system, including the MU-MIMO system model and the explanation on the algorithm used in system. We also have brief introduction about sub-blocking in turbo decoding, finally we compare the performance between the uncoded case and coded case which is using turbo encoding.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.6 no.9
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• pp.2086-2097
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• 2012

A terminal-based dynamic clustering algorithm is proposed in a multi-cell scenario, where the user could select the cooperative BSs from the predetermined static base stations (BSs) set based on dynamic channel condition. First, the user transmission rate is derived based on linear precoding and per-cell feedback scheme. Then, the dynamic clustering algorithm can be implemented based on two criteria: (a) the transmission rate should meet the user requirement for quality of service (QoS); (b) the rate increment exceeds the predetermined constant threshold. By adopting random vector quantization (RVQ), the optimized number of cooperative BSs and the corresponding channel conditions are presented respectively. Numerical results are given and show that the performance of the proposed method can improve the system resources utilization effectively.

• Journal of Internet Computing and Services
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• v.12 no.2
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• pp.113-122
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• 2011

Social Network Service(SNS) has become a hot trend as a web service which helps users construct social relationships in the web and enables online communication. The information about user activities and behaviors obtained from the SNSs is expected to be an useful knowledge source for other services such as recommendation services. Most of previous researches on SNS rely on analyzing overall network topology and surveying the activities in a one-dimensional aspect. This paper propose a system for measuring multi-dimensional interaction through the activities in a SNS. The proposed system delivers an unified profile (consisting of profile and multi-dimension interaction) model from user-activities in Twitter.com. At the experimental section, some meaningful perspectives on a set of the unified profiles are described.

• The Journal of the Korea Contents Association
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• v.5 no.2
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• pp.257-266
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• 2005

As developing of the internet and computer technology, more interests are gathered to the conference service which provides capability of multi-party real-time visual conference. In this paper, we have designed and implemented a SIP-based visual conference system which includes Presence service. The elements of this conference system are user system, which has conference UA(User Agent) capability, presence seuer and conference server. For the presence service, we have adapted publication method which uses SIP PUBLISH message, and with this service various status informations of users are easily acquired. Also invitations and involvements to the conference are easily made through this service. For the conference server which controls establishment and management of multi-party connections, we have included conference event package. This package provides dynamically changing conference informations and users informations through SIP subscription and notification functions.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.15 no.11
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• pp.3892-3912
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• 2021

The recent rapid growth of mobile network traffic places multi-access edge computing in an important position to reduce network load and improve network capacity and service quality. Contrasting with traditional mobile cloud computing, multi-access edge computing includes a base station cooperative cache layer and user cooperative cache layer. Selecting the most appropriate cache content according to actual needs and determining the most appropriate location to optimize the cache performance have emerged as serious issues in multi-access edge computing that must be solved urgently. For this reason, a cache placement algorithm based on comprehensive utility in big data multi-access edge computing (CPBCU) is proposed in this work. Firstly, the cache value generated by cache placement is calculated using the cache capacity, data popularity, and node replacement rate. Secondly, the cache placement problem is then modeled according to the cache value, data object acquisition, and replacement cost. The cache placement model is then transformed into a combinatorial optimization problem and the cache objects are placed on the appropriate data nodes using tabu search algorithm. Finally, to verify the feasibility and effectiveness of the algorithm, a multi-access edge computing experimental environment is built. Experimental results show that CPBCU provides a significant improvement in cache service rate, data response time, and replacement number compared with other cache placement algorithms.

• Journal of the Korea Society of Computer and Information
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• v.18 no.9
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• pp.91-99
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• 2013

In these days, the smart devices are being developed and used repeatedly. But almost E-learning System did not provide these smart devices environment and user's E-learning space is changing from Single-screen environment to multi-Screen environment. Accordingly we configure smart E-learning space based on multi-screen and integrate the multi-media contents for the Smart E-learning service. We present the synchronization techniques to make the multi-screen environment for smart space with Timed Link and design the Timed Button to relate each Screen which is using multi-media e-learning contents.