• Journal of information and communication convergence engineering
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• v.7 no.4
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• pp.525-529
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• 2009

On the limited urban area meteorological data are hard to be collected because of the cost problem. The facilities collecting the data require high installment cost. Recently, the sensor network technique comes to the fore as a solution. Furthermore a mobile phone also becomes to be recognized as a sensor. This paper studies an application to service the meteorological map using mobile phone sensor. A design results for system implementation are introduced in this paper.

• ETRI Journal
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• v.26 no.4
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• pp.360-366
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• 2004

Synchronization Markup Language (SyncML) is a specification of a common data synchronization framework for synchronizing data on networked devices. SyncML is designed for use between mobile devices that are intermittently connected to a network and network services that are continuously available on the network. We have designed and developed a data synchronization system based on the SyncML protocol and evaluated the throughput of the system using the stochastic Petri nets package (SPNP) and analyzed the relationship between the arrival rate and the system resources. Using this model, we evaluate various performance measures in different situations, and we estimate the relationship between the arrival rate and the system resources. From the results, we can estimate the optimal amount of resources due to the arrival rate before deploying the developed system.

• Journal of the Korean Operations Research and Management Science Society
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• v.22 no.2
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• pp.31-44
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• 1997

This paper presents an approximate analytical model to estimate the mean packet walting times at the stations in the IEEE 802, 6 subnetwork of a metropolitan area network. Each station is modeled as a two queue single server system, which serves data packets and requests from downstream stations according to the DQDB protocol. The model estimates the mean waiting time of the requests and in turn, using the discrete time work conservation law, estimates the mean waiting time for packets. Simulation experiments shows that the model accurately works even under very high traffic loads.

• Journal of the Korean Institute of Telematics and Electronics B
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• v.33B no.7
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• pp.51-59
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• 1996

The current network environment is composed of heterogeneous H/W and S/W resources. Integrating CSCW applications in such heterogeneous environments is highly complex. This paper describes the design and implementation of ASS (application sharing server) which supprot sharing of a single application between different operating systems. The ASS supports cooperative work among user group using its own window system (X-windwo or MS-windwos). We adopted improved managing heavy-weight data. ASS also provides development environment for vaious groupware application.

• Journal of KIISE:Information Networking
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• v.31 no.1
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• pp.11-19
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• 2004

P2P network environments provide users with direct data transmission and sharing facilities and those environments can be classified into hybrid P2P network environments and pure P2P network environments according to the arbitration mechanism among the peers in the network. In hybrid P2P network environments, there exists a server that maintains index information for the data to be shared and network isolation does not occur because every peer always keeps connection to the server. In pure P2P network environments, however, each peer directly connects to another peer and gets services without server intervention, and so, network isolation can occur when the mediating peer fails to work. In this paper. we propose a scheme for each peer to keep connection to other peers continuously by maintaining IP addresses of its neighbor peers and connecting to the peers when the mediating peer fails to work. Although the P2P application that uses our proposed framework should obtain one or more IP addresses of the neighbor peers manually, after instantiation, the application can do its job while maintaining connection to the network continuously and automatically. To evaluate our proposed scheme, we measured and analyzed the time for a peer to reconnect to the network when the mediating peer fails and the network isolation occurs.

• Electronics and Telecommunications Trends
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• v.33 no.1
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• pp.68-77
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• 2018

Data deduplication is a common used technology in backup systems and cloud storage to reduce storage costs and network traffic. To preserve data privacy from servers or malicious attackers, there has been a growing demand in recent years for individuals and companies to encrypt data and store encrypted data on a server. In this study, we introduce two cryptographic primitives, Convergent Encryption and Message-Locked Encryption, which enable deduplication of encrypted data between clients and a storage server. We analyze the security of these schemes in terms of dictionary and poison attacks. In addition, we introduce deduplication systems that can be implemented in real cloud storage, which is a practical application environment, and describes the proof of ownership on client-side deduplication.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.16 no.3
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• pp.15-22
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• 2007

An automatic measurement system which collects experimental data at an unmanned station where the networking to the internet could not be accessed was developed. With a Robo-rail accessing to the unmanned station, wireless local networking between server PC at the Rob-rail and client PC at the unmanned station is possible within 30 m from an access point equipment located at the unmanned station. An algorithm for transferring the data file which is saved in the client PC at the unmanned station to the server PC in the Robo-rail was proposed. IEEE-1394 camera was used to collect the data at the client PC. An extracting program from the IEEE-1394 captured images to character data and number data was developed using image processing technique, which drastically reduces the size of data file comparing to that of the raw image file.

• The Journal of the Korea institute of electronic communication sciences
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• v.15 no.4
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• pp.679-686
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• 2020

With global data totals expected to grow to 175 ZB by 2025, data processing capabilities in the network area are becoming more important. In particular, data centers are becoming more stubborn as data usage increases, and the load generated by incoming data should be appropriately distributed to reduce costs and efficiently operate. The SDN technology, which emerged to overcome the limitations of the existing network system, removes rigidity of the Legacy system by separating H/W and S/W from the network equipment, and can be effectively applied to load balancing in the data center using S/W-based flexibility. In this paper, we propose ways to increase efficiency by classifying data received from users by type by utilizing SDN technology, and transmitting and processing classified data in order of response speed of servers in the data center.

• Journal of Korea Society of Digital Industry and Information Management
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• v.6 no.3
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• pp.37-47
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• 2010

In this paper, we propose an UCC broadcasting system in P2P based IPTV environments. Proposed system applies P2P based multiple chain architecture. UCC broadcasting system transfers data from not ISP server but UCC server peer that is included in DSLAM to joined peers. Therefore an algorithm to manage join and departure of peers have to modified. In this paper we propose an algorithm that does not increase an uplink bandwidth of DSLAM that include UCC server when peer joins to the UCC channel. We will show the improved performance of proposed scheme rather than general method with respect to the uplink bandwidth of DSLAM that include UCC server.

• The Transactions of the Korea Information Processing Society
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• v.5 no.5
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• pp.1264-1273
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• 1998

In this paper, we implemented a system which provides more effective conference control than that of video conferencing system has been used on MBone. The system provides multicast service on the non-broadcasting network. It multicasts multimedia data using several MTS(Multipoint Transport Server)s and provides a tightly coupled conference control service with a CCS(Conference Control Server). As providing a tightly coupled conference control service, we can perform effectively video conferencing using this system.