• Journal of Digital Contents Society
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• v.10 no.1
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• pp.61-71
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• 2009

While the broadband network and multimedia technology are being developed, the commercial market on digital contents as well as IPTV has been widely spreading. Especially IPTV is providing various useful services since it makes using multimedia contents easier and more convenient by combining the strong points of both TV and PC system. Until now, IPTV system has been focused on VoD service as a general usages. However, various IPTV services are recently demanded since they can have special features for some specific places and occasions. So in this paper, we propose a design of the download based IPTV system using user-specific channel management. At first, program contents previously scheduled by users are downloaded and are played at settop-box according to the prescribed time table. This system has some advantages of giving users easy access to any wanted media contents in anytime that is IPTV's characteristics. And we can increase stability of services by using time slot distributed download for contents. Because this service can be constructed and maintained at relatively low cost, we confirm that this service model is more suitable to some companies with small infrastructure and special purposes. Accordingly, in this paper, we look into necessary elements and define some protocols for system in order to help other developer build this system.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.6A
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• pp.634-639
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• 2006

In this paper an MMIC 2-stage power amplifier is designed and fabricated for 5GHz wireless LAN applications using $0.5{\mu}m$ gate length PHEMT transistors. The PHEMT gate width is optimized in order to meet the linearity and efficiency of the MMIC power amplifier. The $0.5{\mu}m\times600{\mu}m$ PHEMT for the drive stage and $0.5{\mu}m\times3000{\mu}m$ PHEMT for the amplification stage are the optimized sizes to achieve more than 25dBc of third order IMD at the power level of 3dB back-off from the input P1dB and more than 22dBm output power under a supply voltage of 3.3V. The two-stage MMIC power amplifier is designed to be used for the both of HIPERLAN/2 and IEEE 802.11a because of its broadband characteristics. The fabricated PHEMT MMIC power amplifier exhibits a 20.1dB linear power gain, a maximum 22dBm output power, a 24% power added efficiency under 3.3V supply voltage. The input and output on-chip matching circuits are included on a chip of $1400\times1200{\mu}m^2$.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.15 no.5
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• pp.1125-1134
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• 2011

In this paper a wideband frequency synthesizer is designed for DTV tuners using a $0.18{\mu}m$ CMOS process. It satisfies the DTV frequency band(48~1675MHz). A scheme is proposed to cover the full band using only one VCO and reliable broadband characteristics are achieved by reducing the variations of VCO gains and frequency steps. The simulation results show that the designed VCO has frequency range of 1.85~4.22GHz, phase noise at 4.22GHz of -89.7dBc/Hz@100kHz, gains of 62.4~95.8MHz/V(${\pm}21.0%$) and frequency steps of 22.9~47.9MHz(${\pm}35.3%$). The designed VCO has a phase noise of -89.75dBc/Hz at 100kHz offset. The designed synthesizer has a lock time less than $0.15{\mu}s$. The measured VCO tuning range is 2.05~3.4GHz. The frequency range is shifted down but still satisfy the target range owing to the design for enough margin. The designed circuit consumes 23~27mA from a 1.8V supply, and the chip size including PADs is $2.0mm{\times}1.5mm$.

• Korean Journal of Remote Sensing
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• v.13 no.2
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• pp.99-120
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• 1997

Solar radiation is scattered and absorbed atmospheric compositions in the atmosphere before it reaches the surface and, then after reflected at the surface, until it reaches the satellite sensor. Therefore, consideration of the radiative transfer through the atmosphere is essential for the quantitave analysis of the satellite sensed data, specially at shortwave region. This study examined a feasibility of using radiative transfer code for estimating the atmospheric effects on satellite remote sensing data. To do this, the flux simulated by LOWTRAN7 is compared with CAGEX data in shortwave region. The CAGEX (CERES/ARM/GEWEX Experiment) data provides a dataset of (1) atmospheric soundings, aerosol optical depth and albedo, (2) ARM(Aerosol Radiation Measurement) radiation flux measured by pyrgeometers, pyrheliometer and shadow pyranometer and (3) broadband shortwave flux simulated by Fu-Liou's radiative transfer code. To simulate aerosol effect using the radiative transfer model, the aerosol optical characteristics were extracted from observed aerosol column optical depth, Spinhirne's experimental vertical distribution of scattering coefficient and D'Almeida's statistical atmospheric aerosols radiative characteristics. Simulation of LOWTRAN7 are performed on 31 sample of completely clear days. LOWTRAN's result and CAGEX data are compared on upward, downward direct, downward diffuse solar flux at the surface and upward solar flux at the top of the atmosphere(TOA). The standard errors in LOWTRAN7 simulation of the above components are within 5% except for the downward diffuse solar flux at the surface(6.9%). The results show that a large part of error in LOWTRAN7 flux simulation appeared in the diffuse component due to scattering mainly by atmispheric aerosol. For improving the accuracy of radiative transfer simulation by model, there is a need to provide better information about the radiative charateristrics of atmospheric aerosols.

• Journal of Korea Technology Innovation Society
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• v.10 no.1
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• pp.73-97
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• 2007

R&D into future technologies should be conducted in conjunction with technological innovation strategies that are linked to corporate survival within a framework of information and knowledge-based competitiveness. As such, future technology strategies should be ensured through open R&D organizations. The development of future technologies should not be conducted simply on the basis of future forecasts, but should take into account customer needs in advance and reflect them in the development of the future technologies or services. This research aims to select as segmentation variables the customers' attitude towards accepting future telecommunication technologies and their value orientation in their everyday life, as these factors wilt have the greatest effect on the demand for future telecommunication services and thus segment the future telecom service market. Likewise, such research seeks to segment the market from the stage of technology R&D activities and employ the results to formulate technology development strategies. Based on the customer attitude towards accepting new technologies, two groups were induced, and a hierarchical customer segmentation model was provided to conduct secondary segmentation of the two groups on the basis of their respective customer value orientation. A survey was conducted in June 2006 on 800 consumers aged 15 to 69, residing in Seoul and five other major South Korean cities, through one-on-one interviews. The samples were divided into two sub-groups according to their level of acceptance of new technology; a sub-group demonstrating a high level of technology acceptance (39.4%) and another sub-group with a comparatively lower level of technology acceptance (60.6%). These two sub-groups were further divided each into 5 smaller sub-groups (10 total smaller sub-groups) through two rounds of segmentation. The ten sub-groups were then analyzed in their detailed characteristics, including general demographic characteristics, usage patterns in existing telecom services such as mobile service, broadband internet and wireless internet and the status of ownership of a computing or information device and the desire or intention to purchase one. Through these steps, we were able to statistically prove that each of these 10 sub-groups responded to telecom services as independent markets. We found that each segmented group responds as an independent individual market. Through correspondence analysis, the target segmentation groups were positioned in such a way as to facilitate the entry of future telecommunication services into the market, as well as their diffusion and transferability.