• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2003.05a
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• pp.568-573
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• 2003

This paper describes a study of terrestrial digital TV transmission systems using wideband opto-electronic techniques such as electro-absorption modulators, wavelength division multiplex to support cost effective, high speed, flexible and interactive digital TV networks including ultra-high speed subscriber networks. In particular, the national DTV networks to be installed is required huge amount of cost. Therefore, the network should be carefully designed for DTV, communication and multimedia services in the future. In this paper, wideband optoelectronic DTV systems are suggested.

• Proceedings of the KIEE Conference
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• 1996.07b
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• pp.674-676
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• 1996

In this paper, we suggested the verification method of protective algorithms using EMTDC(Electro-Magnetic Transient DC). In other to verify protective algorithms using EMTDC, we first had to make a user defined component and then applied it to a simple power system with parallel line. By means of this method, We reduced the much time and effort to develop or improve the protective algorithm of digital protective relay. For the future, we apply this method to IDPACS(Integrated Digital Protection and Control System) and intend to implement more reliable digital protective relays.

• Journal of Korea Multimedia Society
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• v.12 no.7
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• pp.979-988
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• 2009

Illegal reproductions and subsequent copyright infringement have curtailed development of digital content industry. Many DRM systems have been developed and utilized for this purpose. However, current DRM system allow only authorized user to access the contents, and as such, redistribution to other user without getting license again entails cumbersome process. Currently, super-distribution system which can be used for redistribution of downloaded contents in more streamlined fashion is being widely conducted. But for streaming type content, it is still very difficult to redistribute with super-distribution system because the client must directly connect to streaming server to access the content. Accordingly, a new DRM streaming service structure is required to allow streamed contents to be redistributed as easily as the downloaded contents. In this paper, we proposed the relay file structure that can connect the streaming server and the user for super-distribution of the streaming contents.

• Journal of Digital Contents Society
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• v.14 no.3
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• pp.343-348
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• 2013

The purpose of this paper is to explore how effectively can learners improve their written skills in English language classrooms with the application of internet tools and software. First, the study compares and analyzes existing research on English writing and describes research background. Second, the study describes how internet tools can be used effectively in the English writing classrooms. For example, learners pick up vocabulary on the internet bulletin board and create sentences using the vocabulary. Third, the study analyzed changes in learners' in-class attitudes towards software and internet tools using comparative measures of performance. Unlike with offline instrumented classes, the in-class application of diverse software and internet tools such as websites and IRC (Internet Relay Chat) had a major impact on the improvement of learners' writing skills.

• Journal of Korea Society of Digital Industry and Information Management
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• v.18 no.4
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• pp.13-21
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• 2022

Recently, in wireless video sensor networks(WVSN), various schemes for efficient video data transmission have been studied. In this paper, a layer based cooperative relaying(LCR) algorithm is proposed for minimizing scalable video transmission distortion from packet loss in WVSN. The proposed LCR algorithm consists of two modules. In the first step, a parameter based error propagation metric is proposed to predict the effect of each scalable layer on video quality degradation at low complexity. In the second step, a layer-based cooperative relay algorithm is proposed to minimize distortion due to packet loss using the proposed error propagation metric and channel information of the video sensor node and relay node. In the experiment, the proposed algorithm showed that the improvement of peak signal-to-noise ratio (PSNR) in various channel environments, compared to the previous algorithm(Energy based Cooperative Relaying, ECR) without considering the metric of error propagation.The proposed LCR algorithm minimizes video quality degradation from packet loss using both the channel information of relaying node and the amount of layer based error propagation in scalable video.

• Journal of electromagnetic engineering and science
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• v.6 no.2
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• pp.103-109
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• 2006

This paper suggests an efficient and comprehensive algorithm of the protection ratio derivation and illustrates some calculated results applicable to the initial planning of frequency coordination in the fixed wireless access networks. The net filter discrimination associated with Tx spectrum mask and overall Rx filter characteristic has been also examined to show the effect of the adjacent channel interference. The calculations for co-channel and adjacent channel protection ratios are performed for the current microwave frequency band of 6.7 GHz including Tx spectrum mask and Rx filter response. According to results, fade margin and co-channel protection ratio reveal 41.4 and 75.2 dB, respectively, for 64-QAM and 60 km at BER $10^{-6}$. It is shown that the net filter discrimination with 40 MHz channel bandwidth provides 28.9 dB at the first adjacent channel, which yields 46.3 dB of adjacent channel protection ratio. In addition, the protection ratio of 38 GHz radio relay system is also reviewed for millimeter wave band applications. The proposed method gives some advantages of an easy and systematic extension for protection ratio calculation and is also applied to frequency coordination in fixed millimeter wave networks.

• KIEE International Transactions on Power Engineering
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• v.2A no.3
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• pp.83-88
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• 2002

An over current relay(OCR), one of the most frequently used protective devices, has time-current characteristics (TCC) to control its trip time according to the current level. It is because an appropriate operating time interval is necessary for coordination with other protective devices. A set of TCC curves of an OCR is, in general, given by the supplier from which a curve is selected by the operator. Therefore, in many cases, it is impossible to consider the operation condition of the given power system exactly. A novel concept of an OCR is suggested in this paper. The proposed OCR has an internal correction module so that it may produce the most adequate TCC curve according to the given protective information for coordination with other devices. With the generated TCC curve, a variety of operation and coordination conditions can be taken into consideration in an effective manner. The suggested OCR is applied to a simple test power system to show very promising results from a coordination point of view.

• Proceedings of the KIEE Conference
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• 2001.11b
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• pp.383-386
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• 2001

Distance relay is tripped by the line impedance calculated at the relay point. Accordingly the accurate operation depends on the precise calculation of line impedance. Impedance can be accurately calculated in case of overhead line. However, in case of power cables or combined transmission lines, impedance can not be accurately calculated because cable systems have the sheath, grounding wires, and cable cover protection units (CCPUs). There are also several grounding systems in cable systems. Therefore, if there is a fault in cable system, these terms will severely be caused much error to calculation of impedance. Accordingly the proper compensation should be developed for the correct operation of the distance relay. This paper presents the distance calculating algorithm in combined transmission line with power cable using wavelet transform. In order to achieve such purpose, judgement method to discriminate the fault section in both sections was proposed using db1 coefficient summation. And also, error compensation factor was proposed for correct calculation of impedance in power cable.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.24 no.9B
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• pp.1601-1607
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• 1999

LMDS(Local Multipoint Distribution Service) is a broadband wireless transmission system in millimeter wave frequency. LMDS system is consisted with relay system to connect between head-end and hub and distribution system to connect between hub and subscribers. In this study, we develop point-to-point relay system to use back-bone system n LMDS network. We develop STM-1 transceiver over 27GHz and analyze the system performance. We can get the similar measurement results comparing the theoretical results and then prove that this system can fit LMDS back-bone network requirement. This is the first system in Korea and we expect this system can apply the various network.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.13 no.6
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• pp.2949-2963
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• 2019

A novel distributed compress-and-forward (CF) system based on multi-relay network is presented. In this system, as the direct link between the source and destination is invalid due to some reasons, such as the limited power, special working environment, or even economic factors, relays are employed to receive analog signals and carry on distributed compressed encoding. Subsequently, the digital signals are transmitted to the destination via wireless channel. Moreover, a theoretical analysis for the system is provided by utilizing the Chief Executive Officer (CEO) theory and Shannon channel capacity theory, and the rate-distortion function as well as the connection between the transmission rate and the channel capacity are constructed. In addition, an optimal signal-to-noise ratio (SNR) -based power allocation method is proposed to maximize the quantization SNR under the limited total power. Simulation result shows that the proposed CF system outperforms the amplify-and-forward (AF) system versus the SNR performance.