• Journal of the Korea Society of Computer and Information
• /
• v.17 no.6
• /
• pp.93-100
• /
• 2012

In this paper we have proposed a linear time algorithm for solving the minimum sharable-bandwidth tree construction problem. The public-shared network is a user generated infrastructure on which a user can access the Internet and transfer data from any place via access points with sharable bandwidth. Recently, the idea of constructing the SVC video streaming delivery system on public-shared network has been proposed. To send video stream from the stream server to clients on public-shared network, a tree structure is constructed. The problem of constructing a tree structure to serve the video streaming requests by using minimum amount of sharable bandwidth has been shown to be NP-hard. The previously published algorithms for solving this problem are either unable to find solutions frequently or less efficient. The experimental results showed that our algorithm is excellent both in the success rate of finding solutions and in the quality of solutions.

• Journal of Korea Society of Industrial Information Systems
• /
• v.13 no.1
• /
• pp.46-56
• /
• 2008

Double Patching is a multicasting technique for a VoD system which has been proposed to provide a true VoD service by making clients share a long patching stream as well as a regular stream For subsequent short patching streams, the technique always makes the long patching stream have extra data that will be played back during a double period of a patching window. In this paper, we propose a technique, using the start time of the latest short patching stream, optimizes Double Patching by deleting the useless data included in the long patching stream when the patching window of the long patching stream closes. The mean requirement for the server's bandwidth to provide the true VoD service is used as a performance metric, and the effect of the request inter-arrival time, the size of the client's local buffer and the video length on the mean bandwidth requirement is evaluated. Performance evaluation result shows that the proposed technique optimizes Double Patching in all cases.

• Journal of the Korea Institute of Information Security & Cryptology
• /
• v.29 no.2
• /
• pp.417-429
• /
• 2019

WPA2-PSK uses a 4-way handshake protocol based on a shared secret to establish a secure session between a client and an AP. It has various security problems such as eavesdropping attacks and the secure session establishment process is inefficient because it requires multiple interactions between client and AP. The WPA3 standard has recently been proposed to solve the security problem of WPA2, but it is a small improvement using the same 4-way handshake methodology. OAuth 2.0 token authentication is widely used on the web, which can be used to keep an authenticated state of a client for a long time by using tokens issued to an authenticated client. In this paper, we apply the dual-token based randomized token authentication technology to the Wi-Fi security protocol to achieve an efficient Wi-Fi security protocol by dividing initial authentication and secure session establishment. Once a client is authenticated and equipped with dual tokens issued by AP, it can establish secure session using them quickly with one message exchange over a non-secure channel.

• Proceedings of the Korea Information Processing Society Conference
• /
• 2011.04a
• /
• pp.1135-1138
• /
• 2011

안드로이드 시장이 급성장함에 따라 안드로이드 기반 어플리케이션에 대한 수요가 많아지고 있다. 그로 인해 3D 그래픽적 기능을 요구하는 어플리케이션에 대한 요구도 늘어났다. 그러나 안드로이드 단말기에서는 3D 처리능력이 데스크 탑과 비교하여 성능과 서비스에 한계가 있다. 그렇기 때문에 VNC(Virtual Network Computing)를 사용하여 고성능의 그래픽을 요구하는 프로그램을 실행할 수 있게 된다. VNC 란 클라이언트에서 데스크 탑으로 접속하여 원격으로 제어하고 그 결과를 그래픽으로 확인하는 프로그램이다. 그러나 기존의 Android VNC 는 해상도가 낮고, 이미지 전송 속도가 느리기 때문에 3D 렌더링 이미지 처리가 불가능했다. 또한 Android VNC 는 인터페이스가 불편하여 입력 오류가 많아 사용이 불편했다는 단점 등이 지적되어 왔다. 본 논문에서는 이를 개선하기 위한 Android Turbo VNC 를 제안한다. Android Turbo VNC는 libjpeg-turbo 코덱을 적용하여 3D 이미지 부분에서 기존의 Android VNC 에 비하여 약 80~120%의 이미지 개선과 이미지 압축률을 4 배정도 높여 CAD 와 같은 고성능의 그래픽을 요구하는 프로그램의 사용을 가능하게 한다. 그리고 Android Turbo VNC 에서는 기존 Android VNC 의 불편한 UI 를 개선하였다. 클라우드 서버에서는 CAD, Document, Game, Video, General 총 5 가지의 프로그램을 서비스하여 그에 맞는 테마 별 UI 를 제공한다. libjpeg-turbo 코덱의 적용을 통해 Android-Turbo VNC 는 수십 장의 설계 도면을 굳이 들고 다니지 않더라도 하나의 테블릿 PC 안에서 보는 것이 가능하게 된다. 테마별 UI 중 CAD 테마는 3D CAD 를 사용하는 산업현장에서 적극적으로 활용될 것으로 기대된다.

• Journal of KIISE:Computing Practices and Letters
• /
• v.5 no.4
• /
• pp.426-439
• /
• 1999

본 논문에서는 웹(World Wide Web)에서 사용자가 손쉽고 편리하게 이용할 수 있는 멀티미디어 대중교통 안내시스템 개발 경험을 소개한다. 개발된 시스템은 클라이언트와 서버 시스템, 경로탐색 시스템, 교통정보 저장 시스템, 노선 및 정류장 관리 시스템으로 구성되어 있다. 클라이언트에서 작동되는 사용자 인터페이스는 직관적으로 이해가 쉽고, 사용이 편리하며 인터액티브한 멀티미디어 대중 교통안내 서비스를 제공한다. 서버 시스템은 교통정보 수집 시스템으로부터 입력되는 데이타와, 경로탐색 시스템, 교통정보 저장 시스템과 연동되어 클라이언트의 요구사항을 처리하고 그 결과를 사용자에게 돌려준다. 수정된 A* 알고리즘을 이용하는 경로탐색 시스템은 최적경로를 탐색하며, 교통정보 저장 시스템은 현재 교통상황, 정류장, 노선, 지도 등의 정보를 저장한다. 노선 및 정류장 관리시스템은 시스템 관리자가 노선 또는 정류장 관리를 서버 화면의 지도상에서 효율적으로 수행할 수 있는 도구이다. 본 논문에서 다루는 대중교통 안내시스템은 Java로 구현하였기 때문에 확장과 이식이 용이하며, 시스템 유지보수 비용이 적게 드는 장점을 가지고 있다. 그리고, 웹 브라우저가 동작되는 환경에서는 어디서나 쉽게 접근이 가능하며 향후 구축될 Intelligent Transportation Systems(ITS)의 한 모듈로써 바로 작동될 수 있을 뿐만 아니라, 현재 인터넷상에서 제공되는 다양한 서비스와도 연동이 가능하다.Abstract This paper introduces our experience for developing a public transportation guidance system, which facilitates the World-Wide Web(WWW) to provide users with easier access and use. The proposed system is composed of four subsystems: client/server system, path search system, traffic data storage system, and traffic raw-data management system. The user interface in clients utilizes Java to furnish users with multimedia data accessibility and interactivity. The server processes clients' requests based on the traffic data coming from remote sensing devices and interacts with the path search system and traffic data storage system to provide users with the results. The path search system, which uses a modified A* algorithm, produces optimal solutions based on dynamic traffic data. The traffic data storage system stores the current traffic information together with the geographical information about the b$us_way routes. The traffic raw-data management system is a graphical user interface which enables the system manager to handle the traffic information easily on the map in the terminal screen. The system has considerable benefits such as portability, scalability, and flexibility since it is implemented using Java. Also, it can be extended to an integrated Intelligent Transportation Systems(ITS) which includes a variety of information on the Internet as well as traffic information.n.

• The KIPS Transactions:PartD
• /
• v.11D no.4
• /
• pp.783-798
• /
• 2004

An e-business client application in ubiquitous mobile computing environment may become disconnected from the enterprise server due to broken communication connections caused by the limitation of mobile computing environments(limited battery life of the mobile device, low bandwidth communication, incomplete wireless communication infrastructure, etc). It Is even Possible that mobile client application Intentionally operates in disconnected mode to reduce communication cost and the power consumption of the mobile device. We use “data hoarding” as a means of providing local autonomy to allow transactions to be processed and committed on the mobile host despite of disconnection. The key problem to this approach is the synchronization problem that serialize potentially conflicting updates from disconnected clients on master objects of the server database. In this paper, we present a new transaction synchronizing method that splits a transaction into a set of independent component transactions and give the synchronization priority on each component taking the possibility of use and conflicts in the server into consideration. Synchronization is performed component by component based un synchronization priority. After the Preferred component of a no bile transaction succeeds in synchronization with the server, the mobile transaction can pre-commit at server. A pre-committed transaction's updated value is made visible at server before the final commit of the transaction. The synchronization of the component with low synchronization priority can be delayed in adaption to wireless bandwidth and computing resources. As a result, the availability of important data updated by mobile client is increased and it can maximize the utilization of the limited wireless bandwidth and computing resources.

• Journal of the Korean Association of Geographic Information Studies
• /
• v.4 no.3
• /
• pp.13-20
• /
• 2001

The purpose of this study is development of the management and guide system for convenient use of new address guide system for systematic management and use of spatial information gained by mapping of numerical map of building and road to large basic new address, survey and input of main gate, decision of the road session, naming and input of road name, grant of numbering of all houses and buildings, new address guide, real life geographical information and added information service on web site in Jecheon-si city area. In this study, the development and establishment of new address management and guide system in local cities are designed by making full use of GIS function of client server based system. A guide system is designed the same database as management system, and it is transformed into Web GIS environment and developed in order to add the various functions of life GIS as well as new address guide. In the result, the effectiveness of new address system and guide of Jecheon-si city could be highly increased owing to not only citizens' easy access but also easy availability of various informations necessary in life by developed its system.

• The Journal of the Institute of Internet, Broadcasting and Communication
• /
• v.16 no.6
• /
• pp.65-73
• /
• 2016

Peer-to-Peer (P2P) systems with super-peer overlay networks show combined advantages of both hybrid and pure P2P systems. Super-peer is a special peer acting as a server to a cluster of generic peers. Organizing a super-peer network is one of important issues for P2P systems with super-peer networks. Conventional P2P systems are based on two-level hierarchies of peers. One is a layer for generic peers and the other is for super-peers. And it is usual that super-peer networks have forms of random graphs. However, for accommodating a large-scale collection of generic peers, the super-peer network has also to be extended. In this paper, we propose a scheme of hierarchically constructing super-peer networks for large-scale P2P systems. At first, a two-level tree, called a simple super-peer network, is proposed, and then a scheme of generalizing and then extending the simple super-peer network to multi-level super-peer network is presented to construct a large-scale super-peer network. We call it an extended super-peer network. The simple super-peer network has several good features, but due to the fixed number of levels, it may have a scalability problem. Thus, it is extended to k-level tree of a super-peer network, called extended super-peer network. It shows good scalability and easy management of generic peers for large scale P2P system.

• Journal of the Korean Association of Geographic Information Studies
• /
• v.19 no.3
• /
• pp.16-28
• /
• 2016

Advancing geo-spatial web technologies and their applications require compatible and interoperable heterogeneous browsers and platforms. Reduction of common or supporting components for web-based system development is also necessary. If properly understood and applied, OGC-based standards can be utilized as effective solutions for these problems. Thus, OGC standards are central to the design and development of web-based geo-spatial systems, and are particularly applicable to web services, which contain data processing modules. However, the application for OGC WPS 2.0 is at an early stage as compared with other OGC standards; thus, this study describes a test implementation of a web-based geo-spatial processing system with OGC WPS 2.0 focused on asynchronous processing functionality. While a binary thresholding algorithm was tested in this system, further experiments with other processing modules can be performed on requests for many types of processing from multiple users. The client system of the implemented product was based on open sources such as jQuery and OpenLayers, and server-side running on Spring framework also used various types of open sources such as ZOO project, and GeoServer. The results of geo-spatial image processing by this system implies further applicability and extensibility of OGC WPS 2.0 on user interfaces for practical applications.

• Journal of KIISE:Computing Practices and Letters
• /
• v.14 no.2
• /
• pp.158-170
• /
• 2008

In response to the changing demands of ever competitive market, SK Telecom has built a new marketing system that can support dynamic marketing campaigns and, at the same time, scale up to the large volumes of data and transactions for the next decade. The system which employs Unix-based client-server (using Web browser interfaces) architecture will replace the current mainframe-based COIS system. The project, named NGM (Next Generation Marketing ), is unprecedentedly large in scale. However, both managerial and technical problems led the project into a crisis. The application framework that depended on a software solution from a major global vendor could not support the dynamic functionalities required for the new system. In March 2005, SK telecom declared the suspension of the NGM project. The second phase of the project started in May 2005 following a comprehensive replanning. It was decided that no single existing solution could cope with the complexity of the new system and hence the new system would be custom-built. As such. a number of technical challenges emerged. In this paper, we report on the three key dimensions of technical challenges - middleware and application framework, database architecture and tuning, and system performance. The processes and approaches, adopted in building NGM system, may be viewed as "best practices" in the telecom industry. The completed NGM system, now called "U.key System," successfully came into operation on the ninth of October, 2006. This new infrastructure is expected to give birth to a series of innovative, fruitful, and customer-oriented applications in the near future.