• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 1999.06a
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• pp.23.1-28
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• 1999

InterSpaceTM is an advanced networked virtual reality system that presents shared three-dimensional computer graphics (CG) worlds via the Internet where multiple users can enjoy synchronous communications with voice, video and text. Users can control their avatars as a surrogate interface. In InterSpace users can walk around and interact with other people and interact with contents. In this paper, we describe the function-distributed architecture used in InterSpace. The architecture enables flexible configuration of server functions and load distribution. It also allows users to select media and client PCs to switch servers dynamically.

• Journal of information and communication convergence engineering
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• v.3 no.2
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• pp.72-75
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• 2005

In this work, we first present our study on the decoding schemes for space-time block code as well as our comments on their complexity. Then, we propose a new modified complex sphere decoding scheme, which has lower computational load than that of conventional complex sphere decoders. In the proposed scheme, the boundary for searching is aided with the intersection of approximate polygon of searching circle and disk of constellation. Therefore, the proposed scheme can reduce the searching boundary while can avoid missing searching points. The performance of the proposed scheme is verified by computer simulation that consolidates our scheme.

• Current Optics and Photonics
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• v.5 no.6
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• pp.627-640
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• 2021

In a free-space coherent optical communication system, wavefront distortion is frequently beyond the correction range of the adaptive-optics system after the laser has propagated through the atmospheric turbulence. A method of residual wavefront correction is proposed, to improve the quality of coherent optical communication in free space. The relationship between the wavefront phase expanded by Zernike polynomials and the mixing efficiency is derived analytically. The influence of Zernike-polynomial distortion on the bit-error rate (BER) of a phase-modulation system is analyzed. From the theoretical analysis, the BER of the system changes periodically, due to the periodic extension of wavefront distortion. Experimental results show that the BER after correction is reduced from 10^-1 to 10^-4; however, when the closed-loop control algorithm with residual correction is used, the experimental results show that the BER is reduced from 10^-1 to 10^-7.

• Journal of the Korea Institute of Military Science and Technology
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• v.27 no.3
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• pp.329-337
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• 2024

Free-space optical communication technology enables the high-speed data transmission and excellent anti-jamming security. We conduct research on satellite-to-ground free-space optical communication links for high-speed transmission of large-capacity surveillance and reconnaissance data. Since the satellite continues to move along its orbit while the optical signal is transmitted between the satellite and the ground, the pointing angle of the beam from the ground terminal needs to be corrected by Point Ahead Angle(PAA) so that the transmitted light reaches the expected location of the satellite. In this paper, we present the algorithm for PAA estimation and control.

• Journal of Engineering Education Research
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• v.13 no.2
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• pp.12-15
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• 2010

Learning community is one of the important pillars of the education in knowledge-based society. How to encourage students' spontaneous participation to the learning community is one of the actual problems to solve for the revolution of the education scheme. In this paper we introduce a strategy to boost the activity of the learning community, which works in the on-line space. The keys for the on-line supporting system for the learning community are to have communication space, trading space and connection with industry. To support activities of each space, we provide an on-line web site which includes a community module, a knowledge market module and an industrial commentary module. Students can start their self-leading study in the communication space, and they can also practice skills for the knowledge management in the knowledge trading space. Through the connection space, they can learn more from the real world critics with help of industry.

• Proceedings of the IEEK Conference
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• summer
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• pp.302-309
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• 2004

The transmission capacity of wireless communication systems may become dramatically high by employ multiple transmit and receive antennas with space-time coding techniques appropriate to multiple transmit antennas. For large number of transmit antennas and at high bandwidth efficiencies, the receiver may become too complex whenever correlation across transmit antennas is introduced. Reducing decoding complexity at receiver by combining array processing and space-time codes (STC) helps a communication system using STC to overcome the big obstacle that prevents it from achieving a desired high transmission rate. Multi-carrier CDMA (MC-CDMA) allows providing good performance in a channel with high inter-symbol interference. Antenna array, STC and MC-CDMA system have a similar characteristic that transmit-receive data streams are divided into sub-streams. Thus, there may be a noticeable reduction of receiver complexity when we combine them together. In this paper, the combination of array processing and STC in MC-CDMA system over slow selective-fading channel is investigated and compared with corresponding existing MC-CDMA system using STC. A refinement of this basic structure leads to a system design principle in which we have to make a trade off between transmission rate, decoding complexity, and length of spreading code to reach a given desired design goal.

• The Journal of the Convergence on Culture Technology
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• v.9 no.5
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• pp.475-480
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• 2023

As the digital fashion show developed through the pandemic period, this study analyzed the literature on the digital fashion show and presented basic data for the design of the metaverse fashion show space. Through keyword analysis, the flow of research was identified, and implications for space design for the metabus fashion show were derived through analysis of space, models and avatars, lighting, and communication. Through keyword analysis, it was possible to understand the conversion process of digital fashion show research in the pandemic situation. Metaverse fashion shows can express stages, avatars, and costumes that are impossible in the real world, but require design considering expressiveness. In the metaverse space, communication can be thought of as a designer's value delivery, digital marketing, and communication with customers.

• Journal of Astronomy and Space Sciences
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• v.13 no.2
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• pp.117-133
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• 1996

In this paper, we describe the architecture and protoccl of stored-and-forward packet communication payload of KITSAT 1/2 microsatellites and then analyze this payload in terms of the probabilities of login success and login refusal, and maximum throughput as quality of service parmaeters.

• Korean journal of communication and information
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• v.34
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• pp.306-340
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• 2006

Mobile communications is argued to reshape and activate the existing space by increasing 'mobile communicability en route' and 'real time interaction.' This study is designed to make an empirical analysis on how different the use of a cellular phone is in each different space. In this study, the space is divided into three distinct parts including the private, social and public space. First, spatial micro-coordination and experience of polysemy of place are widely observed in the use of a mobile phone in the private space. Secondly, it is found that a mobile phone contributes to extending the scope of social contacts which in turn compliments the existing social relationship. Moreover, a full-time intimate community that is connected via a mobile phone results in reshaping the social space. Lastly, the study shows that the usage pattern of a mobile phone varies depending on the type of public space. The technological development is envisaged to lead to more demand for the public space while facilitating the use of the public space.

• The Korean Journal of Air & Space Law and Policy
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• v.20 no.2
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• pp.293-306
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• 2005

In order to bridge the digital divide issues in the Asia Pacific region, Japan initiated the Asia Broadband Program, during implementing E-Japan and U-Japan Plans with collaboration among Asia Pacific Counties. This paper describes first joint experiments that were undertaken in Japan, Singapore and China. Then this paper also describes Japanese efforts to build space infrastructure for development of ICT Society in the Asia Pacific region for further international cooperation to bridge the digital divide Article 1, para. 1, of the Outer Space Treaty of 1967, calls for exploration and use of outer space to be carried out for the benefit and in the interests of all countries irrespective of their degree of economic or scientific development. The augmentation of common benefit from space communication could contribute to bridge the digital divide issues in developing countries in Asia Pacific region. Accordingly, space- infrastructure building would be very important to implement common benefit among countries concerned through international cooperation and collaboration