• The KIPS Transactions:PartD
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• v.8D no.3
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• pp.221-232
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• 2001

Due to rapid advance of wireless communication technology, demand on data services in mobile environment is gradually increasing. Caching at a mobile client could reduce bandwidth consumption and query response time, and yet a mobile client must maintain cache consistency. It could be efficient for the server to broadcast a periodic cache invalidation report for cache consistency in a cell. In case that long period of disconnection prevents a mobile client from checking validity of its cache based solely on the invalidation report received, the mobile client could request the server to check cache validity. In doing so, some schemes may be more efficient than others depending on the number of available channels and the mobile clients involved. In this paper, we propose new cache consistency schemes, effects, efficient especially (1) when channel capacity is enough to deal with the mobile clients involved or (2) when that is not the case, and evaluate their performance.

• Journal of Digital Convergence
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• v.11 no.9
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• pp.201-207
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• 2013

Recently, the interest in a Mobile Office is increasing dramatically and the Smart Phone App Service begin in earnest to be requested in an area of applying SAP system to PC. This study aims to research the system which can be easily implemented with the configuration and Mobile App which cause difficulties in embodying SAP system-based Apps suitable for a mobile environment. First, by realizing SAP system interface that can operate in mobile devices in the form of GUI, assisting the connecting parts of SAP for the users-friendly set-up, providing the communication method of Client, Application, and SAP Service in the form of web service through TCP/IP, and finally showing cases of implementing the method of delivering the data request and result value of Server and Client in the form of XML suggest more effective and new method, the research suggests a new way of making the linkage of SAP more efficient.

• Journal of Korea Spatial Information System Society
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• v.11 no.4
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• pp.56-64
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• 2009

As the Internet has been improved to Web 2.0, it introduces new approaches including Rich Internet Application (RIA) technology such as Flash, AJAX, Silverlight, etc. The RIA which is platform independent technology allows applications to provide rich client-side interfaces, and allows the browser to interact with users without communication to server. In this paper, we propose a method of spatial data service based on RIA technology. Internet map service using spatial data generally requires rich client-side interfaces and various interactions. These features can be provided by the RIA. The proposed method uses Flash developed by Macromedia as RIA technology. It can be applicable on any platform including mobile environment. The spatial data server makes Flash file known as SWF (Shock Wave File) with manipulation code for map and spatial data that is requested by user, and send it to the web browser. Once the web browser receives a SWF, client SWF manipulates user interactions, such as zooming and panning, without communication with server. Experiments that execute the application on various web browsers including mobile web browser and measure time of map interaction are carried out to compare with traditional bitmap based WMS (Web Map Service). As a result of experiments, we have confirmed improvement of interactivity and performance with RIA approach.

• Journal of Digital Contents Society
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• v.10 no.4
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• pp.509-520
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• 2009

The advancement of network & application technology causes a major change for the use of IT(Information Technology) equipment, including computer and mobile system. In the process from beginning with main frame in the 1960s and 70's, through the server-client paradigm in the 1980s and toward the development of network computer since 90's, computer systems are now evolutioning from isolated physical system to complementary network based virtual system[1][2]. In network based computer system, application and data required for operation are stored at not client as local system, but at server[1]. User can use application & data on a server as if those are on a local client, and a client is now toward a developing thin and network friendly system. In this paper, we discuss possible ways for the efficient implementation of thin-client. For the use of remote application & data as if in local environment, we make use of X protocol. Unlike formal simple Client - Server paradigm, we design a Proxy for middle-tier server for the improvement of QoS and session persistence. X server, Xvfb(X virtual frame buffer) are implemented on thin client and Server, respectively and we applied XSMP(X Session Management Protocol) to our framework for session management. In the end, beyond simple transfer of server display, we suggest thin client framework for the transfter of remote server application over internet.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.5B
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• pp.512-521
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• 2003

In this paper, we introduce our experience of the design and implementation of mobile collaboration system(MCS) that support people using mobile devices to participate in cooperative session. There are considerable differences between desktop PC and mobile devices like PDA in processing ability, resolution of display and color degree. In the case of mobile devices, they use different processors and different operating system and they have even differences in ability of executing application. The mobile collaborative system based on T.120 protocol of ITU-T standard compromised of mobile collaboration server, mobile collaboration client, session node and application. We also define the session node in desktop PC in which session control block and communication block runs. This node provide functions of session control block and communication block to mobile collaboration clients and so lighten load of clients. The mobile collaboration server provides information of candidates for session node, session and user to mobile collaboration client. And this server support clients to configure their own session node and manage sessions. Only the mobile collaboration client module and applications including APE are executed in a mobile device when user using mobile devices would like to participate in cooperative session. We implemented mobile collaboration client and applications with JAVA to support platform independency.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.4
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• pp.909-916
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• 2010

In ubiquitous GIS services is possible to use the spatio-temporal data using a mobile device at anytime. Also, client is transmitted latest spatio-temporal data from server. But traditional systems have a problem that the time of transmitting latest information from server to client takes long time because of collecting data periodically. In this paper, we proposed Two-way Synchronization system supporting field update to solve the existing problem. This system uses mobile device for collecting changed data in the real world and sending collected data to server.

• Journal of Industrial Technology
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• v.28 no.B
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• pp.27-32
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• 2008

In this paper, we implement the taxi telematics service system based on location based service(LBS). The system implementation is composed of 3 major parts : the mobile device with which a user requests taxi calls, the taxi client which resides inside a taxi and supports multimedia environments with navigation function, and the server which manages moving taxies and receives user taxi calls. From the mobile device's GPS information, the server finds the closest taxi which is then sent to the user with the mobile device.

• Journal of Electrical Engineering and Technology
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• v.13 no.5
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• pp.2086-2098
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• 2018

Security plays a vital role and is the key challenge in Mobile Ad-hoc Networks (MANET). Infrastructure-less nature of MANET makes it arduous to envisage the genre of topology. Due to its inexhaustible access, information disseminated by roaming nodes to other nodes is susceptible to many hazardous attacks. Intrusion Detection and Prevention System (IDPS) is undoubtedly a defense structure to address threats in MANET. Many IDPS methods have been developed to ascertain the exceptional behavior in these networks. Key issue in such IDPS is lack of fast self-organized learning engine that facilitates comprehensive situation awareness for optimum decision making. Proposed "Intelligent Behavioral Hybridized Intrusion Detection and Prevention System (IBH_IDPS)" is built with computational intelligence to detect complex multistage attacks making the system robust and reliable. The System comprises of an Intelligent Client Agent and a Smart Server empowered with fuzzy inference rule-based service engine to ensure confidentiality and integrity of network. Distributed Intelligent Client Agents incorporated with centralized Smart Server makes it capable of analyzing and categorizing unethical incidents appropriately through unsupervised learning mechanism. Experimental analysis proves the proposed model is highly attack resistant, reliable and secure on devices and shows promising gains with assured delivery ratio, low end-to-end delay compared to existing approach.

• Journal of Broadcast Engineering
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• v.13 no.5
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• pp.586-595
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• 2008

In this paper, we propose an adaptive multi-view video service framework suitable for mobile environments. The proposed framework generates intermediate views in near-realtime and overcomes the limitations of mobile services by adapting the multi-view video according to the processing capability of a mobile device as well as the user characteristics of a client. By implementing the most of adaptation processes at the server side, the load on a client can be reduced. H.264/AVC is adopted as a compression scheme. The framework could provide an interactive service with efficient video service to a mobile client. For this, we present a multi-view video DIA (Digital Item Adaptation) that adapts the multi-view video according to the MPEG-21 DIA multimedia framework. Experimental results show that our proposed system can support a frame rate of 13 fps for 320{\times}240 video and reduce the time of generating an intermediate view by 20 % compared with a conventional 3D projection method.

• Proceedings of the IEEK Conference
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• 2001.06a
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• pp.225-228
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• 2001

We describe the implementation of MPEG-4 Systems for Video on Demand services. We discuss the issues in implementint MPEG-4 Systems, specially Object Description and Elementary stream management(Buffer control, Synchronization). The file-server pump the multiplexed streams to the client through the DMIF. Interaction between server and client is done with User Command(play, pause, stop, fast foward, ...). Stream data are multiplexed off-line. In advance, the file-server read multiplexed streams and pumps it to MPEG-4 terminal(client). Our system can be used in various application not only Video on Demand services, but also Internet broadcasting, remote surveillance, mobile communication, remote education, etc.