• 전기전자학회논문지
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• 제23권4호
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• pp.1224-1229
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• 2019

본 연구에서는 블라인드와 같은 스마트 윈도우 응용을 위해 액정 셀을 제작하였고, 광 투과율이 조절되는 시스템을 개발하였다. 액정 셀의 문턱전압은 1.325V였고, 투과율이 10%일 때 전압은 2.370V를 보여 제작된 액정 셀은 저전압으로 구동됨을 나타내었다. 또한, 액정 셀은 30ms 미만의 응답속도와 80℃/10분간 열을 가한 후에도 안정하게 구동되었다. 구동 시스템은 액정 셀의 인가되는 전압을 0.15V에서 3.53V까지 약 0.5V 간격으로 설계하였고, 실제 인가되는 전압에 따라 액정의 광 투과율이 변화됨을 확인하였다. 이러한 결과는 액정 셀이 스마트 윈도우 응용이 가능성이 있음을 시사한다.

• Journal of the Optical Society of Korea
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• 제19권4호
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• pp.371-375
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• 2015

The impact of equivalent optical bandwidth on the performance of a system using a reflective electroabsorption modulator (R-EAM) based optical source has been experimentally evaluated with signals operating at 2.5 Gb/s and beyond. The equivalent optical bandwidth of our source with a broadband seed light was simply adjusted by using a bandwidth tunable optical filter. From the measurements, we have estimated the required equivalent optical bandwidth of our source for an error-free transmission (@ bit-error-rate of $10^{-12}$) and a forward error correction (FEC) threshold of $2{\times}10^{-4}$.

• 한국환경과학회지
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• 제28권5호
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• pp.521-526
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• 2019

In this study, a solar light collector that collects and transmits solar light required for crop production in a closed plant production system was developed. The solar light collector consisted of a Fresnel lens for collecting solar light, and a tracking actuator for tracking solar light from sunrise to sunset to increase the light collection efficiency. The optical fiber that transmitted solar light was made of Glass Optical Fiber (GOF), and it had an excellent optical transmission rate. After collecting the solar light, the amount of light was measured at 5, 10, 15, 20, 25, and 30 cm distances from the GOF through the darkroom by using a light sensor logger connected to a quantum and pyranometer sensor. Compared with solar light, the light intensity of pyranometer sensor measured at 5 cm was 114% higher than solar light, and 61% at 10 cm. In addition, it was observed that it is possible to transmit the necessary amount of light for growing crops up to about 15 cm (as over 22%) through GOF. Therefore, adding diffusers to the solar light collector should be expected to replace artificial light in plant factories or plug seedlings nurseries for leafy vegetables. More studies on the solar light collection devices and the light transmission devices that have high light collection efficiency should be conducted.

• Journal of Communications and Networks
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• 제17권3호
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• pp.231-240
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• 2015

To facilitate the base station planning in high speed railway communication systems, it is necessary to consider the functional relationships between the base station transmit power and space parameters such as train velocity and cell radius. Since these functions are able to present some inherent system properties determined by its spatial topology, they will be referred to as the power-space functions in this paper. In light of the fact that the line-of-sight path persists the most power of the received signal of each passing train, this paper considers the average transmission rate and bounds on power-space functions based on the additive white Gaussian noise channel (AWGN) model. As shown by Monte Carlo simulations, using AWGN channel instead of Rician channel introduces very small approximation errors, but a tractable mathematical framework and insightful results. Particularly, lower bounds and upper bounds on the average transmission rate, as well as transmit power as functions of train velocity and cell radius are presented in this paper. It is also proved that to maintain a fixed amount of service or a fixed average transmission rate, the transmit power of a base station needs to be increased exponentially, if the train velocity or cell radius is increased, respectively.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제14권1호
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• pp.93-113
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• 2020

According to information theory, non-orthogonal transmission can achieve the multiple-user channel capacity with an onion-peeling like successive interference cancellation (SIC) based detection followed by a capacity approaching channel code. However, in multiple antenna system, due to the unideal characteristic of the SIC detector, the residual interference propagated to the next detection stage will significantly degrade the detection performance of spatial data layers. To overcome this problem, we proposed a modified power-domain non-orthogonal multiple access (P-NOMA) scheme joint designed with space-time coding for multiple input multiple output (MIMO) NOMA system. First, with proper power allocation for each user, inter-user signals can be separated from each other for NOMA detection. Second, a well-designed quasi-orthogonal space-time block code (QO-STBC) was employed to facilitate the SIC-based MIMO detection of spatial data layers within each user. Last, we proposed an optimization algorithm to assign channel coding rates to balance the bit error rate (BER) performance of those spatial data layers for each user. Link-level performance simulation results demonstrate that the proposed time-space-power domain joint transmission scheme performs better than the traditional P-NOMA scheme. Furthermore, the proposed algorithm is of low complexity and easy to implement.

• 한국위성정보통신학회논문지
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• 제11권1호
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• pp.32-36
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• 2016

본 논문에서는 LED(Light Emitting Diode)의 White 조명을 이용한 VLC(Visible Light Communication) 송 수신기를 구현하였다. 가시광 통신과 다양한 환경에서 고속 데이터 전송을 위한 무선 통신 방식의 차이점을 분석하였고 QAM 전송 기법을 이용하여 실제채널을 통과한 심벌의 수신을 확인하였다. 그리고 가시광 통신의 높은 데이터 속도를 얻기 위해 실험을 통해서 고려해야 되는 변수를 찾았다. 또한 주파수 대역을 정하고 거리에 따른 송수신간의 최적의 게인을 찾았다. 효율적인 가시광 통신의 신호 전송 및 검출을 위하여 직교 시퀀스를 이용한 효율적인 신호 검출 기법의 성능을 랩뷰를 이용하여 보였다.

• Journal of Advanced Marine Engineering and Technology
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• 제37권5호
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• pp.527-532
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• 2013

무선 가시광 통신 기술은 실내 또는 수중에서 고속 통신 서비스가 가능하여 많은 주목을 받고 있다. 그러나 가시광에 대한 해수채널의 통신 성능은 현재의 가시광 파장영역 광원과 광 검출기 기술의 한계와 수중 통신채널의 변화로 인한 여러 가지 제약사항들 때문에 실용화를 위해서는 극복해야 할 문제점들이 존재한다. 본 논문에서는 직선상의 가시영역에 있는 해수 환경에서 신호 대 잡음비와 비트 오류율을 분석하였다. 데이터 속도, 통신거리, 감쇠계수등과 같은 파라미터들의 영향에 대하여 연구하였으며, OOK와 L-PPM 변조기법을 적용한 시스템의 모델링과 전산모의를 통하여 수중환경 통신에 대한 강점과 제한점등을 기술하였다.

• Journal of Ginseng Research
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• 제39권4호
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• pp.345-353
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• 2015

Background: Ginseng is a semishade perennial plant cultivated in sloping, sun-shaded areas in Korea. Recently, owing to air-environmental stress and various fungal diseases, greenhouse cultivation has been suggested as an alternative. However, the optimal light transmission rate (LTR) in the greenhouse has not been established. Methods: The effect of LTR on photosynthesis rate, growth, and ginsenoside content of ginseng was examined by growing ginseng at the greenhouse under 6%, 9%, 13%, and 17% of LTR. Results: The light-saturated net photosynthesis rate ($A_{sat}$) and stomatal conductance ($g_{s}$) of ginseng increased until the LTR reached 17% in the early stage of growth, whereas they dropped sharply owing to excessive leaf chlorosis at 17% LTR during the hottest summer period in August. Overall, 6-17% of LTR had no effect on the aerial part of plant length or diameter, whereas 17% and 13% of LRT induced the largest leaf area and the highest root weight, respectively. The total ginsenoside content of the ginseng leaves increased as the LTR increased, and the overall content of protopanaxatriol line ginsenosides was higher than that of protopanaxadiol line ginsenosides. The ginsenoside content of the ginseng roots also increased as the LTR increased, and the total ginsenoside content of ginseng grown at 17% LTR increased by 49.7% and 68.3% more than the ginseng grown at 6% LTR in August and final harvest, respectively. Conclusion: These results indicate that 13-17% of LTR should be recommended for greenhouse cultivation of ginseng.

• 한국항행학회논문지
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• 제9권2호
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• pp.109-120
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• 2005

본 논문에서는 MSSI 보상 기법을 채택한 1,200 km의 WDM 전송 시스템에서의 비트 에러율, 수신 감도, 입사 전력 최소 허용치를 증폭기 간격에 따라 수치적으로 살펴보았다. 변조 파형 형식에 관계없이 수신 감도와 입사 전력 최소 허용치 모두 증폭기 간격이 증가할수록 나빠지는 것을 알 수 있었다. 수신 감도 측면에서는 NRZ 전송보다 RZ 전송을 하는 경우 감도를 개선할 수 있었지만 실제 입사 전력 허용치 면에서는 NRZ가 RZ 전송보다 유리한 것을 확인하였다. 아울러 증폭기 간격을 50 km 이하로 해야만 수신 감도와 입사 전력 최소 허용치 모두 분산 계수, 채널 파장, 펌프광 전력에 비교적 영향을 적게 받는 것을 확인할 수 있었다.

• 한국정보과학회:학술대회논문집
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• 한국정보과학회 2007년도 가을 학술발표논문집 Vol.34 No.2 (A)
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• pp.130-131
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• 2007

Wireless Sensor Network typically incorporates diverse applications within the same network. A sensor node may have multiple sensors i.e. light, temperature, seismic etc with different transmission characteristics. Each application has different characteristics and requirements in terms of transmission rates, bandwidth, packet loss and delay demands may be initiated towards the sink. In this paper we propose Heterogeneous Traffic Oriented Rate Control Protocol (HTRCP) which ensures efficient rate control for diverse applications according to the priority specified by the sink. Moreover. HTRCP ensures the node priority based hop by hop dynamic rate adjustment for high link utilization.