• The Journal of Korean Institute of Communications and Information Sciences
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• v.23 no.4
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• pp.914-925
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• 1998

This paper considers the evaluation of the hybrid acquistion perdformance for the pilot signal in the direct sequence code division multiple access(DS/CDMA) forward link. the hybrid acquisition is introduced by the combination of two schemes, the parallel and serial acquisions. The mean acquisition time of the proposed scheme is derived to consider both the best case(the correct code-phase offsets are included i one subset) and the worst case(the correct code-phase offsets exist at the boundary of two subsets), which are cause by the distribution of the correct code-phase offsets in the subset. Expressions for the detection, false alarm, and miss probabilities are derived for the case of multiple correct code-phase offsets and multipath Rayleigh fading channel. Numerical results present the hybrid acquistion performance with repect to design parameters such as postdetectio integration length in the search and verification modes, subset size, and number of I/Q noncoherent correlators, and compare the hybrid acquistion with the parallel acquistion in terms of the minimum acquistion time under the same hardware complexity.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.2C
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• pp.333-341
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• 2004

Along with the innovative enhancement of Internet technology and the emergency of distributed systems extended from client-server computing, it becomes indispensible and necessary to integrate and interconnect old legacy systems. Since building a distributed system requires consistency of integration, the proper reuse of incumbent systems is critical to successful integration of current systems to distributed ones. CORBA(Common Object Request Broker Architecture) and object wrapping technique can provide middleware solutions that extend the applications of a legacy system with little modification to the application level while keeping client consistency of standard interface. By using these techniques for system integration it is easier and faster to extend services on application development to distributed environments. We propose a model on object wrapping system that can manage, integrate, and separate the functions delivered from CORBA. We apply the object wrapping model specifically to integration of security system interfaces and also perform a test to verify the usability and the efficiency of our model.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.12B
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• pp.1623-1635
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• 2011

Fourth-generation (4G) cellular communication systems must provide different quality-of-service (QoS) to users according to the service type, membership class, and usage case of each user. For the purpose of user's QoS differentiation, we propose an enhanced uplink random access scheme for bandwidth request. More specifically, we divide a bandwidth request channel into two parts: One is a primary region and the other is a secondary region. Then, each region has a unique minimum access class that allows only specific users to perform random access through that region. By doing so, we can reduce collision probability and increase the success probability of bandwidth request. From the perspective of standardization, we presented this scheme in the IEEE 802.16m Session #66 held on March 2010. As a result, the concept of the proposed scheme and required messages were defined in the 802.16m standard.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.42 no.4
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• pp.899-903
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• 2017

In this paper, it is shown the in-vehicle network architecture and implementation for multimedia service which supports Human machine interface of multi-passengers. For multi-passengers' vehicle, it has to be considered the factor of network traffic, simultaneously data transferring to multi users and accessibility to use variety of media contents for passengers compared to conventional in-vehicle network architecture system Therefore, it is proposed the change of network architecture compared with general MOST network, implementation of designed software module which can be interoperable between ethernet and MOST network and accessible interface that passenger can be plugged into MOST network platform using their device based on ethernet network system.

• Journal of the Korean Society of Marine Environment & Safety
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• v.19 no.1
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• pp.71-77
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• 2013

Smart work has been gaining more popularity recently. Smart work means that employees perform their works anytime and anywhere as utilizing the information and communication technology. It can be divided into four categories; the mobile office, the home office, the work-at-center and the tele-cooperation. Among them, the mobile office based on tablet personal computers(PCs) or smart phones, employees can exchange information with tablet PCs or smart phones via mobile radio communication networks and portable terminals. Smart devices such as tablet PCs and smart phones help to access intranet system for requests, approvals, information search whenever employees need. This mobile office system for real-time HSE managing can contribute to improve the productivity and work efficiency in a shipyard. In this study, the main goal is to design the specialized mobile application for the HSE management system on the shipbuilding industry. The mobile application including 10 functions is designed based on ooCBD(object-oriented Component Based Development) methodology.

• Spatial Information Research
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• v.16 no.1
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• pp.79-99
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• 2008

Enterprises as well as central and local governments have tried to apply ubiquitous technology to the actual life on the various types of business and projects. In this paper we develop strategic plan to provide public service on public areas based on needs analysis of public services as well as trend analysis of ubiquitous and web technology. Ubiquitous service model should be based on geospatial web which can incorporate participation and collaboration concepts, as the wire/wireless network system develop rapidly. To achieve this purpose, we suggest the following projects; 1), construction of internet map based on geospatial web technology, 2), development of web contents based on geospatial web, 3), installing ubiquitous equipment, and 4), upgrade Seoul Metropolitan Government's homepage and internet system which can incorporate web 2.0 concepts. Ubiquitous service model should be based on not only development of ubiquitous technology but also needs of consumer such as citizen, enterprises, and public sectors which have an interest in that place. Geospatial web will be the core of development of ubiquitous service models.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.4C
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• pp.581-593
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• 2004

The interest in wireless LAN security is on the increase owing to a role of high-speed wireless Internet infrastructure of wireless LAN. Wi-Fi has released WPA standard in order to overcome drawbacks of WEP algorithm that is security element of current IEEE 802.11-based wireless LAN system. Pairwise key management and group key management in a mixed-mode which supports both terminals running WPA and terminals running original WEP security are very complicate. In this paper, we analyze flaws in WPA authenticator key management state machine for key distribution and propose the countermeasures to overcome the analyzed problems. Additionally, WPA authenticator key management state machine to which the solutions are applied is described. The reconstructed WPA authenticator key management state machine helps the AP perform efficiently group key exchange and group key update in the mixed-mode.

• Journal of the Korea Society of Computer and Information
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• v.15 no.6
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• pp.49-56
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• 2010

In this paper, a joint PHY-MAC layer optimized resource allocation scheme for OFDMA based micro base stations is investigated. We propose cross-layer optimized two-stage resource allocation scheme including cross-layer functional description and control information flow between PHY-MAC layers. The proposed two-stage resource allocation scheme consists of a user grouping stage and a resource allocation stage. In the user grouping stage, users are divided into a macro base station user group and a micro base station user group based on the PHY-MAC layer characteristics of each user. In the resource allocation stage, a scheduling scheme and an allotment of resources are determined. In the proposed scheme, diversity and adaptive modulation and coding (AMC) schemes are exploited as schedulers. Simulation results demonstrate that the proposed scheme increases the average cell throughput about 40~80 % compared to the conventional system without micro base stations.

• 전자공학회논문지 IE
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• v.47 no.1
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• pp.56-60
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• 2010

The widespread development of IT, growth of Web 2.0 application, the proliferation of personal hand held devices with access to the internet, and the availability of wireless networks, each have played an important role in creating the cloud computing model. Cloud computing is a business model and new trend of web application technology. The term is often used in the same context as grid computing or utility computing. In the cloud computing environment, we are able to use the same all of hardware resources in the server and share information easily. In this paper, we aimed a study to apply e-learning part to cloud computing environment. For this purpose, we proposed an application of LMS and LCMS based e-learning in the cloud computing environment. So LMS including LCMS connected to data center of cloud computing.

• The Journal of Korean Association of Computer Education
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• v.5 no.1
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• pp.57-66
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• 2002

Real time multimedia data services have been made possible by the rapid development of the computer and internet technology. Based on the technology, Many multimedia system developer try to use VOD(Video on Demand) and GVA technologies for distance education. However the system has mainly been developed to provide the video screen of good quality in real time and to compose contents efficiently. Not many researches and developments have been made for providing the users that is taking distance education with various types of service using VOD and GVA. Therefore In this paper we have designed and implemented an active on-demand multimedia service system to improve user-side service quality in distance education using VOD and GVA service. The on-demand multimedia service system can prominently help users to save the time and effort to search and select the studying data by this paper enables off-line search functions through E-mail and periodical current awareness service supported by PUSH technology, user oriented information booking supported by SDI service and feedback service.