• Journal of Korea Spatial Information System Society
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• v.11 no.1
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• pp.43-54
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• 2009

As R&D(Research and Development) is going on actively to develop technologies for the ubiquitous computing environment, which Is the human-oriented future computing environment, GIS dealing with spatio-temporal data is emerging as a promising technology. This also increases the necessity of the middleware for providing services to give interoperability in various heterogeneous environments. The core technologies of the middleware are real-time processing technology of data streams coming unceasingly from positioning systems and data stream processing technology developed for non-spatio-temporal data. However, it has problems in processing queries on spatio-temporal data efficiently. Accordingly, this paper designed and implemented the spatio-temporal middleware that provides interoperability between a mobile spatio-temporal DBMS(DataBase Management System) and a server spatio-temporal MMDBMS(Main Memory DataBase Management System). The spatio-temporal middleware maintains interoperability among heterogeneous devices and guarantees data integrity in query processing through real-time processing of unceasing spatio-temporal data streams and two way synchronization of spatio-temporal DBMSs. In addition, it manages session for the connection of each spatio-temporal DBMS and manages resources for its stable operation. Finally, this paper proved the usability of the spatio-temporal middleware by applying it to a real-time position tracking system.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.11 no.1
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• pp.109-113
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• 2011

Recently, according to the development of ubiquitous computing, the u-GIS which not only used in u-Transport, u-Care, u-Fun, u-Green, u-Business, u-Government, and u-City but also used to provides various spatial information such as the location of user is being the core technology of the ubiquitous computing environment. In this paper, we implemented an mobile spatio-temporal Query Processing Systems for handling the Spatio-Temporal Data in mobile equipment.The mobile spatio-temporal Query Processing Systems provides the spatio-temporal data type and the spatio-temporal operator that is expanded by the spatial data type and the spatial operator from OepenGIS "Simple Feature Specification for SQL". It supports arithmetic coding compression techniques that is considered with a spatio-temporal data specific character. It also provides the function of data cashing for improving the importation and exportation of the spatio-temporal data between a embedded spatio-temporal DBMS and u-GIS server.

• Journal of KIISE:Information Networking
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• v.32 no.1
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• pp.80-88
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• 2005

In ubiquitous spaces, a user wants to be provided with a VOD service while moving one space to another freely. Since the traditional VOD system is dependent on user location, the VOD server transmits video data to a single client during a session. If the user moves to another space, he/she should close the old session and make a new request for the same video. However, the location-aware VOD system supports user mobility by closing and opening the session automatically. That is, the VOD system automatically perceives the movement of a user and allows the server to change the data flow so that a client near the user can receive the video data. This paper proposes a location-aware VOD service architecture and a session handoff scheme to provide a mobile user with continuous video delivery and implements a location-aware VOD prototype system based on Jini and Java. In experiment, we show that the proposed handoff scheme has a smaller handoff delay than the other handoff scheme.

• Journal of KIISE:Information Networking
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• v.29 no.2
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• pp.117-128
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• 2002

Virtual LAN (VLAN) is an architecture to enable communication between end stations as if they were on the same LAN regardless of their physical locations. VLAN defines a limited broadcast domain to reduce the bandwidth waste. The Newbridge Inc. developed a layer 3 VLAN product called VIVID, which configures a VLAN based on W subnet addresses. In a VIVID system, a single route server is deployed for address resolution, VLAN configuration, and data broadcasting to a VLAN. If the size of the network, over which the VLANS supported by the VIVID system spans, becomes larger, this single route server could become a bottleneck point of the system performance. One possible approach to cope with this problem is to deploy multiple route servers. We propose two architectures, organic and independent, to expand the original VIVID system to deploy multiple route servers. A course of simulations are done to analyze the performance of each architecture that we propose. The simulation results show that the performances of the proposed architectures depend on the lengths of VLAN broadcasting sessions and the number of broadcast data frames generated by a session. It has also been shown that there are tradeoffs between the scalability of the architecture and their efficiency in data transmissions.

• Journal of Korea Spatial Information System Society
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• v.10 no.4
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• pp.47-58
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• 2008

With the recent development of the ubiquitous computing technology, there are increasing interest and research in technologies such as sensors and RFID related to information recognition and location positioning in various ubiquitous fields. Especially, a standard specification was required for compatibility and interoperability in various RTLS(Real-Time Locating Systems) according to the development of RTLS to provide location and status information of moving objects using the RFID Tag. For these reasons, the ISO/IEC published the RTLS standard specification for compatibility and interoperability in RTLS. Therefore, in this paper, we designed and im plemented RTLS based on the spatial DSMS(Data Stream Management Stream) for efficiently managing and searching the incoming data stream of moving objects. The spatial DSMS is an extended system of STREAM(STanford stREam datA Manager) developed by Standford University to make various spatial operations possible. RTLS based on the spatial DSMS uses the SOAP(Simple Object Access Protocol) message between client and server for interoperability and translates client's SOAP message into CQL(Continuous Query Language) of the spatial DSMS. Finally, we proved the efficiency of RTLS based on the spatial DSMS by applying it for the staff location management service.

• Journal of KIISE:Databases
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• v.30 no.5
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• pp.476-493
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• 2003

Data broadcast is an effective data transmission method from a data base server to numerous mobile clients due to the restrictions on mobile environment such as low wireless communication bandwidth and energy shortage of mobile devices. There are various broadcast methods based on clients' data access frequencies or semantic relationship of data. The broadcast schedule based only on the access frequencies does not consider semantic relations of data, so that when a client needs to access a series of semantically related data, the client has to listen to the wireless channel for a long time. On the other hand, the broadcast schedule based only on semantic relationship of data makes data access time longer when clients highly request specific data which are not semantically related but frequently accessed. In this paper, we present an efficient data broadcast method based on not only data access frequencies but also semantic relationship to improve mobile clients' query response time. The new hybrid broadcast method we propose creates a data broadcast schedule according to the data access frequencies and then the schedule is adjusted to reflect semantic relationship of data. We show our method is efficient by experimental performance analysis.

• Journal of Korea Spatial Information System Society
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• v.2 no.2 s.4
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• pp.25-37
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• 2000

As computer systems of high capacity and high performance recently emerged, various researches about GISs(Geographic Information Systems) have been in progress and many GIS applications have also been developed. From the domestic situation where many people are using mobile devices, because of the recent advances in the mobile technology, we can infer that the time will come when every individual will carry a mobile device with a GPS(Global Positioning System) module resulting from the development of a miniature GPS Module. Therefore, a mobile GIS that can allows users to deal with dynamic GIS data management and perform their tasks while moving will be required. This paper discusses the design and implementation of a mobile GIS using the shareware DBMS, called postgresSQL. The Mobile GIS in which a mobile concept is utilized at the GIS data server makes it possible to insert, delete, update GIS data, to zoom in and zoom out displayed maps, and to locate the user's position on the client device. Therefore, It is possible to manage dynamic GIS data in order to deal with GIS data on the maps while moving, connect various GIS data servers through the middleware, and connected with ITS (Intelligent Transport System) which is one of applications of the Mobile GIS developed in this paper.

• Journal of KIISE:Computer Systems and Theory
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• v.31 no.5_6
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• pp.268-278
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• 2004

In this paper, we describe our experience in the design and implementation of the SMART file system to handle multimedia workload. Our work has three design objectives: (ⅰ) efficient support for sequential workload, (ⅱ) avoiding disk fragmentation, (ⅲ) logical unit based file access. To achieve these three objectives, we develop a file system where a file consists of linked list of Data Unit Group. Instead of tree like structure of the legacy Unix file system, we use single level file structure. Our file system can also access the file based upon the logical unit which can be video frame or audio samples. Data Unit Group is a group of logical data units which is allocated continuous disk blocks. At the beginning of each Data Unit Group, there exists an index array. Each index points to the beginning of logical data units, e.g. frames in the Data Unit Group. This index array enables the random access and sequencial access of semantic data units. SMART file system is elaborately tailored to effectively support multimedia workload. We perform physical experiments and compare the performance of SMART file system with EXT2 file system and SGI XFS file system. In this experiment, SMART file system exhibits superior performance under streaming workload.

• Proceedings of the Korea Database Society Conference
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• 1995.12a
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• pp.109-116
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• 1995

본 논문에서는 그룹웨어(groupware) 또는 CSCW(Computer Supported Cooperative Work) 사용자들이 공유할 데이터들을 그룹 공유 영역에 위치시킨 후 그룹 공유 영역 내의 공유 객체에 대한 접근을 그룹웨어 사용자들에게 제공하는 구조를 제시하고, 그룹공유 영역의 구현을 위해 실시간 그룹웨어 응용에 의존하지 않는 구조를 지닌 공유 영역 서버인 SAS(Shared Area Server)에 대해서 기술한다. 그룹웨어 응용에게 공유 영역에 대한 접근을 제공하는 SACI(Shared Area Client Interface)와 함께 SAS는 하이브리드 구조를 구성하고 SAS와 SACI 그리고 그룹웨어 응용 사이에는 비동기 메시지 전달 방식을 제공한다. 본 논문에서는 실시간 그룹웨어에서 사용하는 공유 객체에 대한 동시성제어를 다루면서 기존 연구와의 차이점을 기술한다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2007.10a
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• pp.465-468
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• 2007

An intelligent home network system using low-power and low-cost sensor nodes was designed and implemented. In Intelligent Home Network System, active home appliances control is composed of RSSI (Received Signal Strength Indicator) based user indoor location tracking, dynamic multi-hop routing, and learning integration remote-control. Through the remote-control learning, home appliances can be controlled in wireless network environment. User location information for intelligent service is calculated using RSSI based Triangle measurement method, and then the received location information is passed to Smoothing Algorithm to reduce error rate. In order to service Intelligent Home Network, moreover, the sensor node is designed to be held by user. The gathered user data is transmitted through dynamic multi-hop routing to server, and real-time user location & environment information are displayed on monitoring program.