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VLC에서 Pseudo Manchester Coding을 사용한 Flicker 최소화에 관한 실험 연구
Md. Shareef Ifthekhar,Nam-Tuan Le,Yeong Min Jang 통신위성ㆍ우주산업연구회 2014 한국위성정보통신학회논문지 Vol.9 No.3
가시광통신은 기존에 설치된 LED등을 사용하기에 무선통신을 위한 방법 중의 하나이다. 본 논문은 이미지 처리 기술을 이용한 광카메라 통신(OCC: Optical Camera Communications) 기술을 제안한다. LED등은 빠른 속도로 on 및 off를 변경할 능력을 가지고있기에 인간의 눈이 인지할 수 없을 정도로 일정한 조도와 함께 데이터를 전송해야 한다. 하나의 데이터 프레임에서 비트 ‘1’ 및‘0’ 사이의 밝기 불균형에 의해 flickering 문제가 발생한다. Manchester code, 4B6B, 8B10B 및 VPPM과 같은 다양한 Run lengthlimited(RLL) coding 기법이 사용될 수 있지만 LED Visible Light Communication is one of the promising technologies for wireless communication due to the possibility to useexisting LED lightening infrastructure to transmit data. LED has the ability to turn on and off very fast enough that ourhuman eyes can’t recognize so it can be used to transmit data via visible light along with illumination. But it faces flickerproblem due to the brightness discrepancies between ‘1’ and ‘0’ bit patterns inside a data frame. Various run length limited(RLL) coding scheme like Manchester code, 4B6B, 8B10B or VPPM can be used to solve flickering problem. So we proposepseudo Manchester codding which can transmit data without modifying LED modulator and demodulator circuit as well assolve flickering problem.
Survey on optical camera communications: challenges and opportunities
Saha, Nirzhar,Ifthekhar, Md Shareef,Nam Tuan Le,Yeong Min Jang IET 2015 IET optoelectronics Vol.9 No.5
<P>Wireless technologies based on radio frequencies (RFs) have always dominated other types of wireless technologies up until now. However, the recent proliferation of media-rich smart devices has pushed the RF spectrum usage to its limit. Therefore RF band expansion towards the optical spectrum is imminent in commercial scale. Indeed, the research on wireless communications using the optical spectrum has gained tremendous ground during the past couple of decades and standardised, respectively, by infrared data association for infrared communication and IEEE 802.15.7 for visible light communication. However, only few shortcomings of the IEEE 802.15.7 standard have led to the development of a revised version, called IEEE 802.15.7r1. This article provides an insight on the activity of the proposed revision of IEEE 802.15.7r1. The proposed revision version targets communication systems that mainly use either image sensors or cameras, known as the optical camera communications (OCC). Leveraging the existing infrastructure, OCC systems will be able to provide ubiquitous coverage in both indoors and outdoors. The authors present their survey focusing on the key technology consideration in IEEE 802.15.7r1, current research status, impairments, enhancements and futuristic application scenarios of the OCC systems.</P>
Experimental Study on Flicker Mitigation in VLC using Pseudo Manchester Coding
셔립입데카르,레투안남,장영민,Ifthekhar, Md. Shareef,Le, Nam-Tuan,Jang, Yeong Min Korea Society of Satellite Technology 2014 한국위성정보통신학회논문지 Vol.10 No.1
Visible Light Communication is one of the promising technologies for wireless communication due to the possibility to use existing LED lightening infrastructure to transmit data. LED has the ability to turn on and off very fast enough that our human eyes can't recognize so it can be used to transmit data via visible light along with illumination. But it faces flicker problem due to the brightness discrepancies between '1' and '0' bit patterns inside a data frame. Various run length limited (RLL) coding scheme like Manchester code, 4B6B, 8B10B or VPPM can be used to solve flickering problem. So we propose pseudo Manchester codding which can transmit data without modifying LED modulator and demodulator circuit as well as solve flickering problem. 가시광통신은 기존에 설치된 LED등을 사용하기에 무선통신을 위한 방법 중의 하나이다. 본 논문은 이미지 처리 기술을 이용한 광카메라 통신(OCC: Optical Camera Communications) 기술을 제안한다. LED등은 빠른 속도로 on 및 off를 변경할 능력을 가지고 있기에 인간의 눈이 인지할 수 없을 정도로 일정한 조도와 함께 데이터를 전송해야 한다. 하나의 데이터 프레임에서 비트 '1' 및 '0' 사이의 밝기 불균형에 의해 flickering 문제가 발생한다. Manchester code, 4B6B, 8B10B 및 VPPM과 같은 다양한 Run length limited(RLL) coding 기법이 사용될 수 있지만 LED 변조기와 복조기 회로를 수정하는 것 없이 데이터를 전송할수 있는 pseudo Manchester codding을 제안한다.