• The Journal of the Korea institute of electronic communication sciences
• /
• v.9 no.8
• /
• pp.915-919
• /
• 2014

Since smart phones are widely used globally, the demand for high-speed mobile communications are increasing. To accommodate the increased communication demand, the next-generation mobile communication services such as LTE-Advanced are deployed. In the LTE-Advanced base stations, the base station schemes of Digital Unit (DU) and Radio Unit (RU) are widely used. Here, the link between DU and RU is called fronthaul link. In the current fronthaul link, a digital optical communication interface is used, which is called Common Public Radio Interface (CPRI). However, the CPRI link cannot support the increased mobile traffic efficiently. Therefore, in this paper, we investigate an alternative technology based on the Radio over Fiber (RoF) to accommodate the increased mobile traffic economically.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.36 no.12B
• /
• pp.1601-1610
• /
• 2011

This paper discusses standardization activities, requirements and enabling technologies for 100G Ethernet and 100G OTN. The need of 100Gbps transport capacity has been gaining greater interest from service providers and carrier vendors. Moreover, optical transport networks based on OTN/DWDM are changing their properties to apply Ethernet traffic which is dramatically increasing. We realize and experimentally demonstrate OTU4 framer with commercial FPGA. The key features of the realized OTU4 framer are parallel signal processing function, multi-lane distribution function, GMP function and FEC function. The realized OTU4 framer has the large signal processing capacity of 120Gbps, which allows to transport about 120Gbps client signals such as $12{\times}10G$ Ethernet and $3{\times}40G$ Ethernet. The realized OTU4 framer has the advantages to quickly adjust to changing markets and new technologies by using commercial FPGA instead of ASIC.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.15 no.10
• /
• pp.6296-6302
• /
• 2014

A new technique, which can increase the channel bandwidth in an optical wireless orthogonal frequency division multiplexing (OFDM) link based on a light emitting diode (LED), is proposed. The technique uses adaptive sampling to convert an OFDM signal to a sparse waveform. In compressive sensing (CS), a sparse signal that is sampled below the Nyquist/Shannon limit can be reconstructed successively with sufficient measurements. The data rate of the proposed CS-based visible light communication (VLC)-OFDM link increases from 30.72 Mb/s to 51.2 Mb/s showing an error vector magnitude (EVM) of 31 % at the quadrature phase shift keying (QPSK) symbol.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.19 no.1
• /
• pp.159-169
• /
• 1994

A multichannel optical slotted ring network is designed using a wavelength division multiplexing(WDM) technique and photonic packet switching devices. The electronics speed bottleneck is removed out of the ring, which allows utilization of the full bandwidth for the optical fiber transmission medium. The ring channel adopts a slotted ring concept with a destination cell remove strategy for the eing access mechanism. The slot size in the ring is selected as the same as that of ATM based cell in order to be used as B-ISDN Access Networks. In this paper, we devised a mathematical method to measure the average transfer delay characteristics of the network. The analytical method turned out to yield accurate results over a broad range of parameters in comparison to simulation results. From the study, we observed the average transfer delay of the network as the network parameters vary.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2018.10a
• /
• pp.480-483
• /
• 2018

In this paper, we study the interference canceling and image sensing processing technology of multiple light sources for high speed transmission in CMOS sensor based visible light communication system. To improve transmission capacity in optical camera communications via image sensors, different data must be transmitted simultaneously from each LED. However, multiple LED light source environments for high-speed transmission can cause interference between adjacent LEDs. In this case, since the visible light communication system generally uses intensity modulation, when a plurality of LEDs transmit data at the same time, it is difficult to accurately detect the respective LEDs due to the light scattering interference of the adjacent LEDs. In order to solve this problem, the ON / OFF state of many LEDs of the light source is accurately recognized by using a dual CMOS sensor, and the spectral estimation technique and the pixel image signal processing technique of each LED are proposed. This technique can accurately recognize multiple LED pixels and improve the total average bit error rate and throughput of a MISO-VLC system.

• Journal of the Korea Society of Computer and Information
• /
• v.19 no.2
• /
• pp.109-115
• /
• 2014

The research on solar energy that we get from nature to cope with energy exhaustion is a very significant and inevitable task for us to do. Along with this, lately, in Korea, as part of new growth engine industry regarding low-carbon green growth, we have selected the LED(Light Emitting Diode) as low power consuming, eco-friendly lighting equipment and have been facilitating research and development on it and creating a variety of new industries utilizing it. What was developed here in this research was the photovoltaic LED lighting system applying lithium polymer batteries equipped with the excellent performance of lithium ion batteries as well as significantly low explosive hazard. Its photovoltaic panel was made to have 100W capacity, and for its power supply system, functional convenience was considered so that it could be equipped with both DC and AC power to be used as household electricity in a variety of ways.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.20 no.10
• /
• pp.229-235
• /
• 2019

A floating photovoltaic generation system is a new concept that combines existing photovoltaic generation technology with floating technology. This is installed in the water not on conventional land and a building. The system is designed as a unit module type that can be connected to other modules according to the power generation capacity, thereby forming a large-scale power generation facility. As a renewable energy source, it is composed of a floating structure, mooring device, photovoltaic power generation facility, and underwater cable. Because this system is installed outdoors, the effect of the wind load on the structure is very large. In this study, the wind loads most affected on the floating photovoltaic generation structure were obtained by computational fluid dynamic analysis. The flow characteristics and wind loads were analyzed for a range of wind orientations and angles of inclination. The analysis showed the position and magnitude of the maximum wind load to the wind direction and the flow characteristics around the solar panel and floating system. The wind load increased with increasing angle of inclination of the panel to the ground.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2013.02a
• /
• pp.306-306
• /
• 2013

본 연구에서는 저가격, 대면적화를 위한 롤투롤 스퍼터를 이용하여, Index matching (히가시 야마 $125{\mu}m$)의 PET 기판 위에 ITO 박막을 성막 시킨 정전용량 방식의 터치 패널용 투명 전극에 대하여 전기적, 광학적, 구조적, 표면적 특성을 분석하였다. ITO 타겟은 미쓰이사(일본의) 주석 함량 5 wt%을 사용하였으며, 롤투롤 스퍼터는 degassing챔버와 스퍼터 챔버가 한 시스템에 구성되었고, Degassing 챔버는 좌우측의 Rewinder/Unwinder 롤러에 의해 감고 풀어지는 PET 기판의 수분 및 가스를 중앙부에 위치한 히터를 통해 제거하며, 수분 제거 후 스퍼터 챔버로 옮겨진 1,250 mm폭의 PET기판을 Unwinder/Rewinder 롤러에 장착하며, Unwinder 롤러로부터 풀려진 PET 기판은 guide 롤러를 거쳐 cooling drum과의 물리적 접촉에 의해 PET 기판의 냉각이 일어나게 된다. ITO 캐소드 전에 장착된 할로겐 히터 상부로 기판이 지나가면서 열처리가 진행되고 열처리 후 두 개의 ITO 캐소드 상부를 지나면서 연속적으로 ITO 박막이 PET 기판에 성막 되게 된다. ITO 박막의 주요 성막 변수인 DC Power, Ar/$O_2$ 가스 유량비, 기판의 속도는 최적으로 고정하고, 성막된 ITO박막의 필름을 각각 고온 챔버에서 $150^{\circ}C$도에서 10 min에서 60 min 동안 각각 열처리를 통한 내열성 테스트를 진행하여 ITO 필름의 특성 향상을 비교 분석하였다. 분석을 위해 전기적 특성은 four-point probe로 측정했고, 투과도는 Nippon Denshoku사(社)의 COH-300A를 이용해 가시광(550 nm)에서 분석했고, FE-SEM으로 ITO박막의 표면 상태를 분석하였다. 또한 Rolling Tester (Z-300)를 이용하여 기계적 안정성을 분석하였다.

• Proceedings of the KIPE Conference
• /
• 2007.07a
• /
• pp.527-529
• /
• 2007

본 논문에서는 120kW급에 이어 단일용량 200kW급 태양광발전용 계통연계형 인버터의 개발에 관한 내용을 설명하고 있다. 200kW급 계통연계형 태양광발전시스템은 22.9kV의 특고압 계통전원에 연계되도록 설계되었으며, 삼상 380V를 22.9kV로 승압 연계하는 2단 절연방식을 채택하였다. 200kW급 인버터는 상용주파수 변압기 절연방식으로 3상4선식 380V 60Hz 출력을 가지고 있으며, 인버터 내부에 200kVA급 변압기와 리액터를 포함하고 있다. 최대 전력점 추종(Maximum Power Point Tracking, MPPT)제어 기법으로 P&O 알고리즘을 적용하였으며, 3상 IGBT 인버터를 DSP로 제어하였다. 본 논문에서는 200kW급 단일용량 인버터를 개발함에 있어, 계통연계 시험, 단독운전 검출 및 방지 시험, 발전량에 따른 효율과 THD 측정 등의 결과를 보이고 있다.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2017.05a
• /
• pp.345-345
• /
• 2017

급격한 도시화 현상으로 많은 인구가 밀집되고 토지를 집약적으로 이용을 하며 시멘트 콘크리트, 블록 등 도로포장으로 인해 불투수층이 증가하여, 폭우와 홍수로 인한 인명과 재산 및 교통체증 등과 같은 다양한 피해를 야기할 수 있다. 침수피해를 발생시키는 인자들은 지표면의 침수심, 침수면적 및 지속시간 등이 있으며, 이러한 인자들을 이용하여 침수에 관한 다양한 연구들이 이루어지고 있다. 본 연구에서 연구할 지역은 도림천 지역 대림 1동, 대림 2동, 대림 3동, 신대방동의 일부분 지역을 대상으로, 침수가 발생한 2010년 강우를 활용하여 도림천 지역의 도시침수를 분석을 하였다. 침수가 일어난 원인으로는 관의 허용용량 초과로 인해 침수가 되었던 것으로 보이고 각 지선관거가 간선관거로 합류하는 과정에서 과부하로 인해 주요 간선관거에서 월류가 발생한것으로 판단된다. 이와 같이 내수배제시설 용량의 초과로 인한 침수가 발생하였을 경우 막대한 피해가 발생하게 되고 이를 저감하기 위해서는 침수심 및 침수면적 등 피해정도를 미리 예측하여 관리 할 수 있는 방안에 대한 연구가 필요하다. 본 연구는 도림천의 우수관망을 이용하여 침수해석모형인 SWMM을 활용하여 문제점들을 파악하였으며, 침수방어능력을 향상 시킬 수 있는 방안을 연구하고자 한다.