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Li-Fi technology

  1. 1. Mini project presentation on: Technology Presented by, Saif aziz absar(1RV11EE047) Laxman Jaygonde(1RV11EE029) Rajesh Kumar(1RV11EE044) Vijeth V S (1RV11EE060) Yatheesha(1RV12EE411) Date of presentation: 05/05/2014
  2. 2. Table of Contents Overview Introduction Objectives Literature survey Methodology Implementation Application Conclusion References
  3. 3. OVERVIEW  In present scenario, Radio waves are being used in communication systems. But visible light can be used to transmit data more faster and efficiently.  Wi-Fi is great for general wireless coverage within buildings, whereas Li-Fi is ideal for high density wireless data coverage in confined area and for relieving radio interference issues.  Li-Fi comprises a wide range of frequencies and wavelengths, from the infrared through visible and down to the ultraviolet spectrum.  Here a sinusoidal signal has been transmitted from one device to another through visible light.
  4. 4. Introduction  LI-FI stands for Light-Fidelity.  LI-FI is transmission of data through illumination , i.e, sending data through a LED light bulb that varies in intensity faster than human eye can follow.  Li-Fi can be thought of as a light-based Wi-Fi. That is, it uses light instead of radio waves to transmit information.  And instead of Wi-Fi modems, Li-Fi would use transceiver-fitted LED lamps that can light a room as well as transmit and receive information.
  5. 5.  Wi-Fi (Wireless Fidelity) uses 2.4-5GHz RF to deliver wireless Internet access and its bandwidth is typically limited to 50-100 megabits per second (Mbps).  Optical wireless technologies sometimes called visible light communication (VLC) and more recently referred to as Li-Fi (Light Fidelity) on the other hand, offer an entirely new paradigm in wireless technologies in terms of communication speed, flexibility and usability.
  6. 6. OBJECTIVE  The main objective of the project is to provide an efficient, low cost, secure, digitally controlled and fast data transfer technique which can be used as an alternative for conventional data transfer technique Wi- Fi.  At the same time the project also lets us to use more efficient light source i.e., LED.  Our project also aims at a communication tool in public places which comes up with transfer of data at a faster rate over a wide spectrum.
  7. 7. LITERATURE SURVEY  The technology truly began during the 1990's in countries like Germany, Korea, and Japan where they discovered LED's could be switched on & off to send information.  At TED, Haraald Haas demonstrated a data rate of transmission of around 10Mbps – comparable to a fairly good UK broadband connection. Two months later he achieved 123Mbps.  On 12th July 2011, he used a table lamp with an LED bulb to transmit a video of blooming flowers that was then projected onto a screen behind him. During the event he periodically blocked the light from lamp to prove that the lamp was indeed the source of incoming data.
  8. 8. Methodology  LED i.e, Light emitting diode can be switched on and off at a faster rate. The operating speed of LED is less than 1 μs, which the human eye can’t detect, causing the light source to appear continuously.  This invisible on-off activity enables a kind of data transmission using binary codes.  Switching on the LED is a logical ‘1’, switching it off is a logical ‘0’.  It is possible to encode data in the light by varying the rate at which LED’s flicker on and off to give different strings of 1s and 0s.  Modulation is so fast that human eye doesn’t notice.
  9. 9. Design of LI-FI Li-Fi architecture consists numbers of Led bulbs or lamps, many wireless devices such as PDA, Mobile Phones, and laptops. Important factors we should consider while designing Li-Fi as following: • Presence of Light • Line of Sight(Los) • For better performance use fluorescent light & LED
  10. 10. IMPLEMENTATION  The original information proposed to be sent was data packets consisting of text or voice information, this would then be decimated by a suitable ADC or any other converter to produce data bits which were to be modulated on a suitable algorithm, keeping primarily noise immunity in mind.  The original idea was to modulate the sinusoidal signal using BPSK technique and use two DSK kits to transmit the sine wave. But since it required a 100KHz ADC and DACs, which are hardly available, two arduino processors were used instead of DSK kits.  The sinusoidal signal is given from signal generator to the arduino to which an LED is connected.
  11. 11.  The sinusoidal signal is sampled using arduino at a particular sampling frequency and then it is given to the LED.  The LED blinks according to sampled signal and thus the signal is converted to digital signal.  The signal transmitted by the LED is received by a photoreceptor which is connected to another arduino.  The signal received is decoded and is given to a low pass filter.  The output of the low pass filter is observed in a CRO which is a sinusoidal signal.
  12. 12. BPSK technique • Consider a sinusoidal carrier. If it is modulated by a bi-polar bit stream according to the scheme illustrated in Figure below, its polarity will be reversed every time the bit stream changes polarity. • This, for a sine wave, is equivalent to a phase reversal (shift). The multiplier output is a BPSK 1 signal.
  13. 13. • The wave shape is ‘symmetrical’ at each phase transition. • This is because the bit rate is a sub-multiple of the carrier frequency ω/(2π). • In addition, the message transitions have been timed to occur at a zero-crossing of the carrier. • The information about the bit stream is contained in the changes of phase of the transmitted signal.
  14. 14. Components used  One DSK6713 kit  One Function generator  One CRO  Two ARDIUNO processors  One visible light LED  One photodiode  one self designed low pass filter(2 resistors, 2 capacitors, bread board)  Connecting wires
  15. 15. Comparison between LI-FI and WI-FI
  16. 16. APPLICATIONS  Smart Lighting: Any private or public lighting including street lamps can be used to provide Li-Fi hotspots and the same communications.  Mobile Connectivity: Laptops, smart phones, tablets and other mobile devices can interconnect directly using Li-Fi. Short range links give very high data rates and also provides security.  Hospital & Healthcare: Li-Fi emits no electromagnetic interference and so does not interfere with medical instruments, nor is it interfered with by MRI scanners.  Aviation: Li-Fi can be used to reduce weight and cabling and add flexibility to seating layouts in aircraft passenger cabins where LED lights are already deployed.  Underwater Communications: Due to strong signal absorption in water, RF use is impractical. Acoustic waves have extremely low bandwidth and disturb marine life.  Vehicles & Transportation: LED headlights and tail-lights are being introduced. Street lamps, signage and traffic signals are also moving to LED.  Location Based Services (LBS): Highly accurate location-specific information services such as advertising and navigation that enables the recipient to receive appropriate, pertinent information in a timely manner and location.
  17. 17. ADVANTAGES  Li-Fi can solve problems related to the insufficiency of radio frequency bandwidth because this technology uses Visible light spectrum that has still not been greatly utilized.  High data transmission rates of up to 10Gbps can be achieved.  Since light cannot penetrate walls, it provides privacy and security that Wi-Fi cannot.  Li-Fi has low implementation and maintenance costs.  It is safe for humans since light, unlike radio frequencies, cannot penetrate human body. Hence, concerns of cell mutation are mitigated.  Extremely high color fidelity.
  18. 18.  Instant start-time  Dynamic Dark - Brightness modulation of lamp output to enhance video contrast  Easy thermal management  Trouble-free integration into existing light engine platforms.  Wide spectrum over the visible wavelength range
  19. 19. DISADVANTAGES  Only works if there is direct line of sight (LOS) between the transmitter and receiver.  Data transmission can be easily obstructed by opaque obstacles.  The use of very high frequencies (400-800THz) limits it to very short distances and point to point communications only.  Interferences from external light sources like sun light, normal bulbs, and opaque materials in the path of transmission will cause interruption in the communication.  High installation cost of the VLC systems.  A major challenge facing Li-Fi is how the receiving device will transmit back to transmitter.
  20. 20. RESULT Whenever the phototransistor is brought in line of sight of LED and the output of low pass filter is observed in CRO, the output obtained is as shown below. It is observed that the above shown sinusoidal waveform is replaced by random noise as soon as the phototransistor is moved away from the line of sight of LED.
  21. 21. Conclusion The possibilities are numerous and can be explored further. If this technology can be put into practical use , every bulb can be used something like a Wi-Fi hotspots to transmit wireless data. Since light is the major source for transmission in this technology it is very advantageous and implementable in various fields that can’t be done with the Wi-Fi and other technologies. Hence the future applications of the Li-Fi can be predicted and extended to different plat-forms like education fields, medical field, industrial areas and many other fields.
  22. 22. References 1) ‘Li-Fi: Data through Light’, The Institute of Engineers, Technorama Magazine, Volume 62, pp. 41, December 2012. 2) http://www.newscientist.com/article/ will-lifi-be-the-new-wifi.html 3) http://caledonianmercury.com/the-futures-bright-the-futures-li-fi 4) ”Visible-light com-munication: Tripping the light fantastic: A fast and cheap opti-cal version of Wi-Fi is coming”, The Economist, dated 28 Jan 2012. 5) en.wikipedia.org/wiki/Li-Fi
  23. 23. THANKYOU

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