Design of Clean and Green Smart Visible Communication System with LED/LASER

1. INTRODUCTION:

Communication systemhas been employed to transfer the data and information between source and destination. Nowadays communication system has becomethe essential part of our life. It is not only needed for entertainment but also in allimportant field like education, business, airtrafficcontrol, satellite etc. It‘s not possible to run this world withoutcommunication even to each other for one day. Time the communication was only form of speech so used to cover small distance. With the time, technology also developed and a better way of communication with cables started, which was more efficient and covered more distance than before. Later advance version of this was adopted i.e. OFC (Optical Fiber Communication). OFC was more secured, fast, compact, easy to installed and less costly, but the only drawback was wired. So we moved to wireless communication through microwaves. Microwaves have overcome all limitations of previous mode ofcommunication but due toincreasing demand of data the spectral becomes sodense that Electro Magnetic Interference is increasing rapidly and any time lead to network crash. Furthermoreelectromagnetic waves has hazardous effect on humanbody.By taking all these issues in account weare trying to use this new mode of communication called Li-Fi, which is a wireless communicationsame as present with only difference of wavelength,here we are using visible light spectrum in place ofmicrowave which overcomes all shortcomings listed above.

LASER and LED are used as reliable sources of communication in Visual Light Communication (VLC). However, LASER is used more often due to its inherent properties over LED. LED is also limited by distance even though it forms a relatively cost effective wireless transmissionlink. Blue –Greenlaser is good choice for underwater communication. In these paper we have done experiment with LED and different color of laser and observed the speed, the distance covered, spectrum width and many more parameters.

The information from a personal computer (PC) in any kind of format is first coded into a string of pulse electrical signals by microcontroller (MCU) using the interface circuit. These signals drive LED using a LED driver circuit. As a result, there will be signal conversion from electronic to optical level. Due to flickering property of LEDs, the information and light will only be appearing as normal light from an LED for an observer. This information is then send over the channel depending on the various channels we have to experiment on. Our channels include, air, fresh and saline water. At the receiver, the photodiode will detect the optical signal and then convert into electrical signal. The signals thus detected can be amplified using an amplifier setup. The data thus receiver after amplification or signal processing will be send to thePC receiver using the RS -232 interface. The experiment is repeated in 3 different scenarios.

The effect of interference is high as the communication is involving light. The communication is limited by factors like distance, number of proper receivers, effect of saline water in underwater communications etc. Different digital modulation schemes are deployed to reduce the signal error rate and enhance the received signal power. Theunderwater communication was a real challenge due to the effect of saline water. Thedistance measured between transmitter and receiver was different in clear water and saline water. Results are plotted in table 1.

There should be line of sight between the transmitter and receiver. Else the communication will be suspended. The speed of transmission and the size of LED are related inversely. A simple microchip LED can generate speeds up to 150 Mbps. A LED smaller than that can generate speeds in Giga Hertz range. The field of view should be less to have a better performance. Field of view is the angle of spread increased the current to the LED, the intensity was good and it yielded better results. But it will damage the LED. When LEDs (white LED) are used for communication, the range was very less; in the order of centimeters. When replaced by LASER (650 nm red dot) the range substantially increased to several meters. The effect of natural light was found minimal as the receiver is capable of distinguishing the flickering of LED from natural light. Still, experiments in dark environment gave fast and clear results. The temperature ranges while experiment was conducted was in the range of 25 to 30degrees. When more LEDs were attached to the transmitter thus forming an array of LEDs, it is found that there is significant amount of Inter Symbol Interference in the received signal due to spread of the signal. The use of directive LEDs reduced the interference to a good level. The numbers of LEDs were then increased to three to see how the distance affects faithful reproduction. The distance, as expected is a factor as the information was not received after a particular distance. The details are listed in the table. The PIN photodiode was used and MSM metal semiconductor Metal photodetectors were also used while testing. OmittedAvalanche photodiode due to cost.

We also measured signal intensity using an LED array and function generator setup andholding the receiver at a distance to measure the maximum

The received signal is in mille Volts and it‘s plotted against distance in centimeters. There was minimal background noise as the transmitter and receiver were arranged properly. The experiment is repeated underwater and the transmission distance was poor in the range of few centimeters. So, repeated the same experiment with LASER to get a better result. The blue green LASER with a wavelength of 470-570 nm was used for the purpose. The result thus obtained is shown in graph. The measurement is made around 10 times and the number of successful data transmission were plotted for a distance of 1 meter between transmitter and receiver.

LEDs like an array there are chances of inter symbol interference and performance degradation. Although LEDs are a cheaper option in underwater

• The natural light doesn‘t seem to disturb the receiver much which made the communication smooth.(while using LASER) • When repeated the experiment in dark, the received image was a little better than when received in light. • The effect of any sort of obstacle completely disturbed the image and the image was failed to be reproduced • The issue while transmission was time which is limited by factors like baud-rate, LASER used, Modulation schemeused, photodiode used etc. The transmissionwasnot proper/possible with higher baud rates used. There are methods to convert using different sources. LASER is preferred over LED when transmission distance is more. Transmission can be done and modulation schemes can be enabled to have a better performance. LED source is relatively cheap and can be implemented when such applications are to be dealt.

1. D. Tsonev, S. Sinanović, and H. Haas, ―Enhanced Subcarrier Index. 2. Modulation (SIM) OFDM‖ in Proc. Of IEEE Global Communications Conference (IEEE GLOBECOM 2011), Houston, Texas, USA, 5-9 Dec. 2011. 3. Li-Fi (Light Fidelity)-The future technology In Wireless Communication Neha Singh, International Journal of advances in computing & communications, Vol. 1, 2013 4. M. Afgani, H. Haas, H. Elgala, and D. Knipp, ―Visible Light Communication using OFDM‖ in Proc. of the 2nd International Conference on Testbeds andResearch Infrastructures for the Development of Networks and Communities(TRIDENTCOM), Barcelona, Spain, March 1-3 2006, pp. 129-134. 5. M. Di Renzo, H. Haas, and P.M. Grant, ―Spatial Modulation for Multiple-Antenna Wireless Systems: A Survey‖, IEEE

6. H. Haas, ―Wireless Data from Every Light Bulb‖, TED Website, Aug. 2011. [Online]. Available: http://bit.ly/ted_vlc. 7. H. Elgala, R. Mesleh, and H. Haas, ―Indoor Optical Wireless Communication: Potential and State-of-the- Art‖, IEEE Communications Magazine, vol. 49, no. 9, pp. 56-62, Sep. 2011, ISSN: 0163-6804. 8. Visible Light Communication blog site. http://visiblelightcomm.com.

9. technopits.blogspot.comtechnology.cgap.org/ 2012/01/11/a-lifi-world

10. http://www.extremetech.com/extreme/ 147339-micro-led-lifi-where-every-light-source-in-the-world-is-also-tv-and-provides-gigabit-internet-access 11. Visible-light communication: Tripping the light fantastic: A fast and cheap opticalversion of Wi-Fi is coming‖, Economist, dated 28Jan 2012

1. Mrs. Rakhi Sharma, a research scholar is post graduate in Electronics and communications Engg. She is pursuing her research in the innovative and front line research in Energy efficient communication system (a future wireless internet communication), from the Faculty of Electronics and communication Engineering, Mewar University, Gangrar, Chottorgarh, Rajasthan. She has attended the conferences andpresented the paper on LI-Fi Technology 2. Prof. Y. P. Singh, Professor, E.C.E. He has worked about 34 years as Lecturer, Dean of academics & Principal in many Engineering institutions and organization. He has also served with Training and Technical Department, Government of Delhi, almost for 17 years. He has about 276 research paper published in National and 964 papers published in international journals in his credit. He has been selected and awarded by Govt. of Delhi as adjudged as outstanding work. He has submitted his 2 patents and is in process. He has also has been awarded as ―Star of Asia Award ―an international award, by Global achievers foundation. He has been awarded the Best Technical Director (Research) in Haryana in 2014, and Best Technical Director (Research) in Delhi 2015. He is also an expert and Master Trainer for the Teachers, empanelled by SCERT/NCERT. He is also the guide of research scholar for almost dozen of Universities.

Research Scholar, Mewar University, Rajasthan rakhi1181@gmail.com