I. IntroductionLi-Fi or Light Fidelity is a technology that uses light emitting diodes to transmit data wirelessly. It was first demonstrated at a TED talk in 2011 by German physicist Harald Haas. This is a free band that does not need any license. Hence it is cheaper than Wi-FI. Wi-Fi, is a popular technology that allows an electronic device to exchange data or connect to the internet wirelessly using radio waves the visible light spectrum is larger than the radio spectrum which provides better flexibility in its use. Communications over a very high speed with a theoretical limit of 10 GB per second. The technology is capable of transferring thousands of streams of data simultaneously, in parallel, at higher speeds, with the help of special modulation, using a unique signal processing technology. The term Li-Fi was first used in this context by Harald Haas in his TED Global talk on Visible Light Communication. “At the heart of this technology is a new generation of high brightness light-emitting diodes�, says Harald Haas from the University of Edinburgh, UK,� Very simply, if the LED is on, you transmit a digital 1, if it’s off you transmit a 0,�Haas says, “They can be switched on and off very quickly, which gives nice opportunities for transmitted data�.Fig.1 Harald HaasIt is possible to encode data in the light by varying the rate at which the LEDs flicker on and off to give different strings of 1s and 0s.The LED intensity is modulated so rapidly that human eye cannot notice, so the output appears constant. With the use of light radiating diodes Li-Fi technology transfers data through wireless. Li-Fi is a new exemplar for photosensitive wireless technology to provide unprecedented connectivity within a localized data centric environment. There has been a complete shift in wireless technology due to increase demand Li-Fi is such a free band which is license free that is why it is less at cost than Wi-Fi. With the use of special intonation using a distinctive signal processing technology thousands of streams of data can be transferred simultaneously at higher speed. Li- Fi is useful in aircraft because the lights present above head can be used for data transmission. It is useful in controlling traffic at traffic signals as it communicates with LED lights of cars. Where there is difficult to amateur optical fibers LI-Fi is used. The new Li-Fi technology can be well managed very easily and it is pretty simple. At one corner you will be having a led which will be working as a light source and on the other corner a Light Sensor or a photo detector. Light Sensor detect light as soon as the LED light starts glowing and will give an output of eitherbinary1 or binary0.[pic]Fig.2 Li-Fi EnvironmentIf the LED is on, you transmit a digital 1, if it’s off you transmit a 0.What is VLC?Visible light communication (VLC)-“A potential solution to the global wireless spectrum shortage� Li-Fi (Light Fidelity) is a fast and cheap optical version of Wi-Fi, the technology of which is based on Visible Light Communication (VLC).VLC is a data communication medium, which uses visible light between 400 THz (780 nm) and 800 THz (375 nm) as optical carrier for data transmission and illumination. It uses fast pulses of light to transmit information wirelessly.Li-Fi Technology at a Glance!The LED bulb will hold a micro-chip that will do the job of processing the data. The light intensity can be manipulated to send data by tiny changes in amplitude. This technology uses visible spectrum of light, a part of the electromagnetic spectrum that is still not greatly utilized. In fact the technology transfers thousands of streams of data simultaneously, in parallel, in higher speeds with the help of special modulation, using a unique signal processing technology. Some Points of Li-FiThe light used to transmit the data is called D-light by Harald Hass, the inventor of Li-Fi. In future data for laptops, Smartphone’s, and tablets can be transmitted through the light in a room by using Li-Fi. Security would be a snap—if you can’t see the light, you can’t access the data.II. CONSTRUCTIONThe LI-FI product consists of 4 primary sub-assemblies:• Bulb• RF power amplifier circuit (PA)• Printed circuit board (PCB)• EnclosureThe PCB controls the electrical inputs and outputs of the lamp and houses the microcontroller used to manage different lamp functions. An RF (radio-frequency) signal is generated by the solid-state PA and is guided into an electric field about the bulb. The high concentration of energy in the electric field vaporizes the contents of the bulb to a plasma state at the bulb’s center; this controlled plasma generates an intense source of light. All of these subassemblies are contained in an aluminum enclosure• FUNCTION OF THE BULB:-At the heart of LI-FI is the bulb sub-assembly where a sealed bulb is embedded in a dielectric material. This design is more reliable than conventional light sources that insert degradable electrodes into the bulb. The dielectric material serves two purposes; first as a waveguide for the RF energy transmitted by the PA and second as an electric field concentrator that focuses energy in the bulb. The energy from the electric field rapidly heats the material in the bulb to a plasma state that emits light of high intensity and full spectrum. The design and construction of the LI-FI light source enable efficiency, long stable life, and full spectrum intensity that is digitally controlled and easy to use. “There are over 14 billion light bulbs worldwide, they just need to be replaced with LED ones that transmit data�.III. HOW LI-FI WORKS?[pic]Fig. 3 block diagram of Li-fi communicationIn order to know the working of Li-fi we need to know the necessity for Li-fi .With the vast development in living the use of gadgets and invention of new gadgets is increasing which lead to the technological developments. There are many situations in which people get frustrated with the dull performance signals of Wi-Fi at a place with many network connections in seminars conferences etc. Li fi fulfils these needs .this fantabulous idea first striked the mind of Harald Haas from University of Edinburgh, UK, in his TED Global talk on VLC.His idea was very simple that if the LED is “on� then the digital 1 can be transmitted and if the LED is off� then the digital 0 can be transmitted. LED’s can be switched on and off very quick. For transmitting data this way all that we require is LED’s and controller that code data into Led’s. Parallel data transmission can be done by using array of LED’s or by using red, green, blue LED’s to alter light frequency with the frequency of different data channel.Advancements and enhancements in this field generate a speed of 10 gbps! But amazingly fast data rates and lowering band widths are not the only reasons that enhance this technology. Li-fi usually is based on light and so it can be probably implemented in aircrafts and hospitals that are prone to inference from radio waves .Unlike Wi-Fi, Li-Fi can work even under-water which makes it more advantageous for military operations. Radio waves are replaced by light waves in data transmission called Li- Fi. Light emitting diodes can be switched on and off very much faster than the human eye allowing the light source to appear continuously.The data transmission is done through binary codes which involve switching on LED can be done by logic 1 and switch off using logic 0.The encoding of information in light can therefore be identified by varying the rate at which the LED’s flicker on and off to give strings of 0’s and 1’s.visible light communication is this method of using rapid pulses of light to transmit information wirelessly. To further get a grasp of Li-Fi consider an IR remote. It sends a single data stream of bits at the rate of 10,000-20,000 bps. Now replace the IR LED with a Light Box containing a large LED array. This system is capable of sending thousands of such streams at very fast rate. Light is inherently safe and can be used in places where radio frequency communication is often deemed problematic, such as in aircraft cabins or hospitals. So visible light communication not only has the potential to solve the problem of lack of spectrum space, but can also enable novel application. The visible light spectrum is unused; it’s not regulated, and can be used for communication at very high speeds.IV. COMPARISON BETWEEN LI-FI &WI-FILI-FI is a term of one used to describe visible lightcommunication technology applied to high speed wireless communication. It acquired this name due to the similarity to WI-FI, only using light instead of radio.Li-Fi technology is based on LEDs for the transfer of data. The transfer of the data can be with the help of all kind of light i.e. Light may be Invisible, Ultraviolet or Visible part of spectrum. The speed of the internet is incredibly high and the user everything in just a few minutes.V. ADVANTAGES• Capacity• Availability• Efficiency• High Security• Easy To Use• Fast Data Transfer• Harmlessness• Low-costVI. DISADVANTAGES:Still there are some backdrops like it can only transmitWhen in the line of sight well it can be sorted �Visible-light communication: Tripping the light Fantastic: A fast and cheap optical version of Wi-Fi is coming�, Economist, dated 28Jan 2012 out someday I hope. “There has been a lot of early hype, and there are some very good applications�.VII. APPLICATIONS1. Education systemsAs with the advancement of science the latest technology is the LIFI which isthe fastest speed internet access service. So this will leads to the replacement of WIFI at institutions and at companies so that all the people can make use of LIFI with same speed intended in a particular area.2. Extends our life spanAs operation theatres do not allow WIFI due to radiation concerns. Usage of WI-FI at hospitals interferes with the mobile and pc which blocks the signals for monitoring equipments. Therefore the replacement for this Wi-Fi is Li-Fi as Hass has mentioned in his TED TALK that LIFI has 10,000 times the spectrum of Wi-Fi. Because the lights are not only al-lowed in operation theatres but also the most dazzling fixtures in the room.3. Reduction in accident numbersAt traffic signals, we can use LIFI in order to communicate with LED lights of the cars by the number of accidents can be reduced. Data can be easily transferred by making use of LIFI lamps with the street lamps.4. Replacement for others technologiesThis technology doesn’t deal with radio waves, so it can easily be used in the places where Bluetooth, infrared, WIFI and Internet are banned. In this way, it will be most helpful transferring medium for us. It includes other benefits like: • *A very wide spectrum over visible wave length range. • * Extremely high colour fidelity.• *Instant start time.• *Easy terminal Management.• *Dynamic dark i.e. brightness Modulation of lamp output to enhance video contrast. • *Trouble-free integration into existing light engine platform. • Li-Fi is the upcoming and on growing technology acting as competent for various other developing and already invented technologies. Since light is d 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 platforms like education fields,medical field, industrial areas and many other fields.VIII. CONCLUSIONThe possibilities are numerous and can be exploredfurther. If this technology can be put into practical use, every bulb can be used something like a Wi-Fi hotspot to transmit wireless data and we will proceed toward the cleaner, greener, safer and brighter future.The concept of Li-Fi is currently attracting a great deal of interest not least because it may offer a genuine and very efficient alternative to radio-based wireless. As a growing number of people and their many devices access wirelessinternet, the airwaves are becoming increasingly clogged, making it more and more difficult to get a reliable, high-speed signal. This may solve issues such as the shortage of radio-frequency bandwidth and also allow internet wheretraditional radio based wireless is not allowed such asaircraft or hospitals. One of the shortcomings however is that it only work in direct line of sight.CONCLUDING REMARKS:• Overcomes the limitations of radio spectrum• High speed of 10 Gbps can be achieved• Lifi can solve the foressential problems of wireless communications these daysIX. REFERENCE1. http://en.wikipedia.org/wiki/Li-Fi2. http://gimt.edu.in/clientFiles/FILE_REPO/2012/NOV/23/1353645362045/69.pdf 3. http://www.collegelib.com/t-li-fi-technology-seminar-report-abstract.html 4. the-gadgeteer.com/2011/08/29/Li-Fi-internet-at-the speed- of-light/ 5. http://the-gadgeteer.com/2011/08/29/li-fi-internet-at-the-speed-of-light/6. http://www.oledcom.com/FR/Press%20release%20MWC2013.pdf 7. ill Li-Fi be the new Wi-Fi?, New Scientist, by Jamie Condliffe, dated 28 July 2011. 8. http://www.eiccit.org/Proceedings/LI-FI%20the%20Latest%20Technology%20in%20Wireless.pdf 9. �Visible-light communication: Tripping the light fantastic: A fast and cheap optical version of Wi-Fi is coming�, Economist, dated 28Jan 2012 10. http://www.digplanet.com/wiki/Li-Fi
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