• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.12C
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• pp.1606-1616
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• 2004

This paper introduces a technique for generating an appropriate template signal via modeling of minimum-phase stable ARMA (Auto-Regressive Moving Average) system for coherent impulse communication systems. It has been well known that the transmitted impulse signal becomes deformed because of dispersive and resonant characteristics. Accordingly, in spite of using ideal template signal at the correlator, these impairments degrade overall performance attributed to low level of coherence. To increase the degree of coherence, our proposed scheme realizes A3U system derived by Gaussian pulse signal, which simulates the overall characteristic of transfer function in between transmit and receive wideband antennas so as to generate an appropriate template signal in a form of output. The performance of proposed scheme will be shown in results from computer simulations to verify its affirmative impact on impulse communication system with regarding several distinctively shaped antennas.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.5C
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• pp.351-360
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• 2008

In cellular mobile radio systems with frequency reuse, the interference signals degrade the channel estimation and signal detection performance due to the low signal-to-interference ratio near coverage boundaries. When the preamble pilot sequences from different cells are orthogonal or located in disjointed positions, they can be used for multi-cell channel estimation and interference cancellation. In time-varying channels caused by Doppler spread, data pilot symbols are needed for channel estimations. However, data pilot symbols are usually located in identical positions for the overhead reduction, which degrades the channel estimation performance. In this paper, we demonstrate a significant amount of performance improvement is achieved by multiplying different pseudonoise(PN) sequences to the data pilot symbols from adjacent interference cells. In particular, for detection scheme using maximal ratio combining(MRC) and inter-cell spatial demultiplexing(ISD), quantitative performance gain of spectral efficiency for different values of Doppler frequency and interference power is presented.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.5A
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• pp.479-486
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• 2008

In this paper, an efficient training symbol design with m-sequence is proposed for the MIMO-OFDM based next generation wireless transmission system which supports gigabits per second data rate. In the traditional blute force method, the preamble design is based on the case by case comparison with the system requirements. This paper discusses a training symbol design methodology for the MIMO-OFDM system based on the m-sequence which has been widely used in the spread spectrum communication areas due to its good correlation characteristics. Also the step-by-step design and performance verification method within the limited search space is discussed. The proposed method targets the design of the training symbol which satisfies system requirements for the packet based MIMO-OFDM wireless communication system including automatic gain control(AGC), timing synchronization, frequency and sampling offset estimation, and MIMO channel estimation.

• The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
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• v.6 no.3
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• pp.55-67
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• 1995

The error rate equations of MPSK and DS/MPSK radio signals transmitted through the m-distributed fading channel in Gaussian noise and tone interference environments have been derived. Using the derived equations, the error rate performance is evaluated and shown as functions of carrier-to-noise ratio, carrier-to-interference ratio, processing gain, fading index and the number of diversity branches. The derivation has been done for two cases. The first case assumes that only the signal is undergoing the influence of fading, and the second case assumes that both signal and interference are undergoing the influence of fading simultaneously. From the obtained results, we have known that the error performance of MPSK signal is improved by using diversity technique and direct sequence spread spectrum technique even in a fading environment. Also comparing the error rate performance of two cases, the latter is worse than the former.

• The Journal of the Acoustical Society of Korea
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• v.38 no.2
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• pp.207-213
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• 2019

In this paper, we evaluate the communication performance of convolutional code with block interleaving in a frequency-selective channel. Block interleaving is a technique for spreading and rearranging digital data streams. A block interleaving technique is applied to improve the performance by dispersing the concentration of burst errors in a frequency-selective channel. As a result of evaluating the performance of the convolutional code with block interleaving in the water tank experiment, There was no difference in the performance of convolutional codes using block interleaving in a frequency-selective channel. However, in the frequency-selective channel, the convolutional code with block interleaving has a gain of 2dB, and it is confirmed that the underwater acoustic communication performance is improved.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.7
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• pp.423-429
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• 2019

Recently, a variety of methods for the performance improvement of ultra-high speed wideband wireless transmission systems have been suggested. This paper proposes a space-frequency (SF) block coded single side band (SSB) single carrier (SC)-frequency division multiple access (FDMA) transmission system. In the proposed SSB SC-FDMA system, SF block code is implemented with the complex conjugates, which are formed from discrete Fourier transform (DFT) spreading of pulse amplitude modulation (PAM) signals. As a result, transmit diversity gain can be obtained in the proposed SF block coded SSB SC-FDMA system without any significant increase of the system computational complexity. The simulation result shows that the signal-to-noise power ratio (SNR) performance of the proposed SF block coded SSB SC-FDMA system is approximately 4 dB better than the SNR performance of the conventional SSB SC-FDMA system with single transmit antenna at a symbol error rate (SER) of $10^{-2}$.

• Convergence Security Journal
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• v.23 no.5
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• pp.35-43
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• 2023

As digital infrastructure increases connections and convergence progress rapidly in all areas, and it is most important to ensure safety from cyber infringement or hacking to continue national growth. Accordingly, it examines the obstacles to cyber threat information sharing, which is the basis for responding to cyber infringement, and suggests ways to improve efficiency. First of all, information sharing is divided into three areas: the government, cyber security companies, small and medium-sized enterprises and individuals and the requirements are checked from their respective positions. We will supplement this and explore ways to strengthen cybersecurity and provide economic benefits to each other. Therefore, national and public organizations will propose policies to create an cybersecurity industry ecosystem with a virtuous cycle that leads to diversification of cyber threat information sources, strengthening cybersecurity for general companies and individuals, and creating demand for the cybersecurity industry. The results of the study are expected to help establish policies to strengthen national cybersecurity.

• Proceedings of the Korean DIstribution Association Conference
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• 2001.11b
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• pp.145-163
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• 2001

최근 인터넷 상거래가 급속히 확산되면서 기업의 경쟁이 실물세계와 가상세계에서 발생하는 현상이 전개되고 있다. 즉, 유통경로의 측면에서 볼 때 기존의 물리적 세계에 존재하는 전통적인(오프라인) 유통경로와 사이버공간에 존재하는 가상(온라인) 유통경로가 서로 경쟁하는 형국이 벌어지고 있는 것이다. 유통경로간 경쟁의 중심부에는 고객이 자리잡고 있다. 어떤 경로든 소비자의 욕구를 정확히 파악하고, 이들에게 최상의 유통서비스를 제공하는 경로는 생존·번영할 수 있을 것이다. 사실 현재 진행되고 있는 논의들과 현상들을 볼 때, 어느 한 유통경로가 다른 유통경로를 완전히 대체하는 제로섬 게임의 양상은 나타나고 있지 않다. 즉, 상당기간 두 유통경로는 상호 병존할 것으로 보인다. 본 연구는 이러한 점에 초점을 맞추어 이들 두 경로가 자신들만의 차별화된 경쟁우위를 가지고 생존할 수 있는 마케팅전략을 구상하기 위해 시도되었다. 이러한 전략을 제시하기 위해서는 우선 이들 두 경로상에서 소비자의 구매(쇼핑)행동은 어떻게 다른가에 대한 비교연구가 선행되어야 할 것이다. 본 연구는 온라인 유통경로와 오프라인 유통경로에서 소비자 구매행동의 차이를 비교분석 하는데 그 목적을 두고 있다. 특히 제품유형별로 온라인과 오프라인에서 구매속성중요도가 어떻게 달라지는가를 확인. 검증해 보기 위해 시도되었다. 캐주얼의류, 여행상품, 음악CD를 가지고 인터넷 사용자 500명을 대상으로 온라인조사를 실시한 결과, 온라인과 오프라인에서 구매속성 중요도에는 유의한 차이가 나타났다. 이 결과를 토대로 오프라인 매장과 온라인 매장이 어떻게 차별화해야 하는가에 대한 시사점을 제시하였다.통계적인 차이가 있었다(P<0.05). 계육내 CLAisomer는 1, 2, 3% 급여구에서 각각 12.23, 18.74, 25.67 mg/g으로 처리구간에 현저한 차이를 보였다(P<0.05). 본 연구의 결과 CLA의 급여는 SBO와 CT에 비하여 증체량을 개선하고 혈중HDL을 높여주는 경향을 보였지만 ND항체가는 개선되지 못하였다.으며, 그 효과는 농도에 의존적이었다, 고콜레스테롤 투여군(HC)의 분변 중 총 지질과 중성지방 농도는 정상대조군(C)에 비해 다소 높았고, 총 콜레스테롤의 경우는 유의적으로 높게 나타났다. 그러나 뽕잎첨가군(HC5M과 HC10M)의 총 지질, 중성지방 및 콜레스테롤 농도는 콜레스테롤 투여군(HC)에 비해 분변으로 배설량이 증가하는 현상을 보였다. 이상의 결과를 살펴보면 뽕잎 분말은 고콜레스테롤식이를 섭취하는 경우 혈청과 간장의 지질수준은 떨어뜨리고, 분변중 지질배설량을 상승시키는 효과가 현저한 것으로 보인다.둘째. 1990년대 한국과 미국 패션시장의 가격과 품질간의 상관계수의 범위는 제품군별. 산업범주별 로 상이한 분포를 보이고 있었다. 패션제품군별로 보 면, 한국의 경우는 가장 높은 '여행용가방(r = 0.707)' 에서 가장 낮은 '자외선 차단화장품(r = -0.58)'까지, 그리고 미국 패션제품군의 상관계수의 범위는 '팬티 스타킹'의 0.820에서 '남성용 런닝슈즈'의 -0.472까지의 분포를 나타냈다. 마지막으로, 제품의 가격과 품질에 대한 정보를 소비자가 알 경우 얻을 수 있는 소비자의 구매이득 을 추산한 결과 패션제품시장에서 완전한 품질정보를 가지고 있다고 가정한 '현명한 사람'은, 최고가격의 제품만을

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.29 no.1
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• pp.36-41
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• 2018

This paper presents an implementation of a millimeter-wave(W band) multiflare-angle horn antenna. The proposed antenna is a multimode dual-polarized square horn having equal E- and H-plane beamwidths and consists of a multimode generating section, a four-square-waveguide exciter, orthomode transducers, and power combiners for the sum pattern formation. The antenna structure has been designed to allow for easy fabrication and the designed antenna has been fabricated to a precision of ${\pm}0.02mm$ by layer-by-layer machining and diffusion bonding. The input reflection coefficient and the radiation pattern of the fabricated antenna have been measured using a network analyzer and a far-field test facility. Measurements show that the proposed antenna has 17.7~18.3 dBi gain, $25.2{\sim}28.5^{\circ}$ beamwidth, and an input VSWR between 1.02~1.75, within ${\pm}0.5GHz$ from the center frequency.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.10 no.4
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• pp.539-549
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• 1999

In this paper, the bit error rare (BER) performance of DS/CDMA DQPSK communication system in the presence of multi access interference, impulsive noise and Nakagami fading is investigated. The DS/CDMA DQPSK communication system adopts Maximum Ratio Combining (MRC) diversity reception and error correcting BCH code technique to enhance system performance. Using the derived error probability equation, the error rate performance of DS/CDMA DQPSK communication system has been evaluated and shown in figures to discuss as a function of impulsive index(A), Gaussian noise to impulsive noise power ratio($\Gamma$'), multi access interference(Κ), Nakagami fading parameter(m), the number of diversity branch (Ｌ), the number of error correction symbol (t), PN code sequence length(N) and $E_b/N_0$. The error performance of DS/CDMA-MDPSK signals improve by adopting MRC diversity and BCH(15,7) coding technique in the environment of impulsive noise plus Nagakami fading. From the results, we known that proposed system is affected by multi access interference, impulsive noise and Nakagami fading in radio communication system environment. Also, BER performance of DS/CDMA DQPSK communication system cam be improved increasing either the power of desired signal or the value of Gaussian noise to impulsive noise power ratio. And BCH(15,7) code technique is more effective to restrain the affection of multi access, interference, impulsive noise and Nakagami fading in DS/CDMA DQPSK communication system than MRC diversity reception technique.