• Journal of the Korean Society for Railway
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• v.16 no.6
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• pp.460-465
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• 2013

Radio propagation in a high-speed railway is affected by ground reflective waves that are due to irregular reflection by the railway track, which consists of rails, sleepers, and gravel. This paper provides a train radio propagation model that simulates an irregular track reflective wave as a random variable. A simulation study using the train radio propagation model shows that the path loss exponent is around 3.0, indicating a reduced path loss compared to the value of 4.0 in the general mobile radio environment. Regressive analysis of the received signal strength indicators measured in the Gyeongbu high-speed railway showed the results identical to those of the simulation. These results confirm the train radio propagation model and can be applied to the coverage estimation and the design of a train radio network.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2001.05a
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• pp.157-160
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• 2001

본 논문은 근거리에서의 차량간 통신에 밀리미터나 광전파를 분석하는데 효과적인 Ray Tracing방법을 도입하여 오율특성을 분석하였다. 분석환경으로는 간섭신호에 강한 장점을 지니며 산소흡수에 의한 감쇠가 크며 주파수 재사용효율이 좋은 60GHz 대역에서의 비트오율을 분석하였다. 전파모델로 지면반사파, 콘크리트벽에 의한 반사와 옆 도로를 달리는 차량에 의한 반사를 고려한 Two-Ray 라이시안 채널에서의 다중접속자에 의한 DS/CDMA 시스템의 비트오율특성을 분석하여 검토하였다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.5 no.2
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• pp.263-268
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• 2001

This paper analyzes error probability performance adopted the Ray Tracing method efficiently analyzing millimeter wave or optic wave in Inter Vehicle Communication(IVC). Analysis environment analyzed bit error characteristic in 60㎓ band with very powerful to multipath wave, to be large to oxygen absorption and to be good to frequency reuse efficiency. We analyzed bit error characteristic of DS/CDMA system by multi access user in Two-Ray rician channel adopted reflect wave of grand, reflect wave of concrete wall and reflect wave of driving vehicle at side road. Improvement performance is adopted MRC diversity.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2001.10a
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• pp.680-683
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• 2001

본 논문은 대기에 의한 흡수율이 매우 큰 60GHz 대역에서의 전파 특성을 이용하여 근거리 차량간 통신 시스템에 적용하여 시스템을 분석한다. 근거리 차량간 통신에서는 전파환경이 직접파와 지면반사파 그리고 측면 차량, 도로벽면에 의한 다중경로가 존재하는 라이시안 분포의 특성이 존재하며 이러한 특성을 고려하여 밀리미터파 분석에 효율적인 Raytracing방법을 도입하여 차량간 통신 시스템을 분석한다. 또한 차량간 통신은 운전자의 안전성과 연결되어지기 때문에 매우 높은 신뢰성이 요구되어지며 따라서 MC-CDMA/QPSK 방식을 도입하여 시스템의 신뢰성을 확보하였으며 수신 성능 향상을 위한 개선기법으로는 BCH 부호화 기법을 적용하여 시스템의 성능을 비교 분석 한다.

• Journal of the Institute of Convergence Signal Processing
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• v.15 no.1
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• pp.9-14
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• 2014

The path loss data was re-calculated according to the distance between the base station and a mobile station in the mobile telecommunications network. In this paper, the averaged path loss data was plotted with the conventional path loss models(free space, plane earth, Hata model ${\ldots}$). The standard deviations for the 2 Km, 1 Km, 0.5 Km-interval averaged path loss were 2.29 dB, 3.39 dB, 4.75 dB, respectively. Additionally, the derivative values for the 2 Km, 1 Km, 0.5 Km-interval averaged path loss were evaluated to find the positions with more than 1 times or 2times of the standard deviation. The situations with the sharply fluctuated path loss were calculated to 5 positions in the 2 Km interval, to 7 positions in the 1 Km interval, to 19 positions in the 0.5 Km interval, respectively. And, the exact distances between the base station and a mobile station were found with the sharply fluctuated path loss.

• Journal of Korean Society of Forest Science
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• v.78 no.1
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• pp.30-34
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• 1989

Effects on noise attenuation of the hedge species, Thuja orientalis L. and Euonymus japonicus Thunb., widely used as road side hedges, were analysed at the frequencies of 1,000, 2,000 and 3,150 Hz., respectively. The present experiments were carried out both in the field and in a Semianechoic Chamber. As increasing the distances from the noise source, attenuation rates of noise level were increased at high frequencies. But the attenuation rates of the noise level at low frequencies showed varied as the distances increased, and this trend appeared to be caused by the influence of ground waves. Generally, in this experiment, Thuja orientalis L., which is a coniferous species, showed more effective on the abilities of noise attenuation than that of Euonymus japonicus Thunb., which is a broad-leaved evergreen species.