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hether you’re using wireless internet in a coffee shop,stealing it from the guy next door, or competing for bandwidth at a conference, you have probably gotten frustrated at the slow speeds you face when more than one device is tapped into the network. As more and more people and their manydevices access wireless internet, clogged airwaves are going tomake it.

One German physicist, Harald Haas has come up with asolution he calls “data through illumination” –taking the fibberout of fiber optic by sending data through an LED light bulbthat varies in intensity faster than the human eye can follow.It’s the same idea band behind infrared remote controls but farmore powerful.

Haas says his invention, which he calls D-Light,can produce data rates faster than 10 megabits persecond, which is speedier than your average broadbandconnection. He envisions a future where data for laptops,smart phones, and tablets is transmitted through the light in aroom. And security would be snap – if you can’t see the light,you can’t access the data.


Li-Fi is typically implemented using white LED light bulbs at the downlink transmitter. These devices are normally used for illumination only by applying a constant current. However, by fast and subtle variations of the current, the optical output can be made to vary at extremely high speeds. This very property of optical current is used in Li-Fi setup.The operational procedure is very simple-,data from the internet and local network is used to modulate the intensity of the LED light source if any undetectable to the human eye. The photo detector picks up signal, which is converted back into a data stream and sent to the client.
The client can communicate through its own LED output or over the existing network. An overhead lamp fitted with an LED with signal-processing technology streams data embedded in its beam at ultra-high speeds to the photo-detector. A receiver dongle then converts the tiny changes in amplitude into an electrical signal, which is then converted back into a data stream and transmitted to a computer or mobile device.

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Li fi report Li fi report Document Transcript

  • Li-Fi 2013 Li-Fi: The latest tech in Wireless Communication A Seminar Project Report submitted by: Vivek Kumar Jha in partial fulfillment for the award of the degree of Bachelor in Technology in Computer Science & Engg. under the able guidance of Ms. Sarita Das (Project Guide) & Ms. Nalini Prabha Behera (HOD, CSE).
  • 1 Acknowledgement I take this opportunity to express my deep sense of gratitude and thankfulness to my project guide, Ms. Sarita Das andMs. Nalini Prabha Behera(HOD, CSE) under whose able guidance I have been successful in finishing the project work. Vivek Kumar Jha Regd. No – 1001215240 Branch – CSE EAST
  • 2 Certificate This is to certify that Master Vivek Kumar Jha, 6th Sem, CSE Branch has completed & duly submitted his seminar report hard copy correctly within the stipulated time. His work was found to be genuine & correct. Ms. N.P. Behera Ms. Sarita Das Ms. S. Mishra (H.O.D, CSE) (Project Guide) (Principal, EAST)
  • 3 Contents Acknowledgement_____________________________1 Certificate____________________________________2 Abstract_____________________________________3 Introduction__________________________________4 System Design________________________________6 Present Scenario______________________________15 Issues with Radio Waves_______________________16 Li-Fi as an alternative__________________________17 Light for wireless Communication________________19 Implementation_______________________________19 Achieving Communication through light___________25 Overcoming the issues_________________________26 Application__________________________________27 Conclusion__________________________________28 Reference___________________________________29
  • 4 Abstract hether you’re using wireless internet in a coffee shop,stealing it from the guy next door, or competing for bandwidth at a conference, you have probably gotten frustrated at the slow speeds you face when more than one device is tapped into the network. As more and more people and their manydevices access wireless internet, clogged airwaves are going tomake it. One German physicist, Harald Haas has come up with asolution he calls “data through illumination” –taking the fibberout of fiber optic by sending data through an LED light bulbthat varies in intensity faster than the human eye can follow.It’s the same idea band behind infrared remote controls but farmore powerful. Haas says his invention, which he calls D-Light,can produce data rates faster than 10 megabits persecond, which is speedier than your average broadbandconnection. He envisions a future where data for laptops,smart phones, and tablets is transmitted through the light in aroom. And security would be snap – if you can’t see the light,you can’t access the data. W
  • 5 Introduction to Li-Fi i-Fi is transmission of data through illumination by taking thefiber out of fiber optics by sending data through a LED lightbulb that varies in intensity faster than the human eye canfollow. “At the heart of this technology is a newgeneration of high brightness light-emitting diodes”, saysHarald Haas from the University of L
  • 6 Edinburgh, UK.”Verysimply, if the LED is on, you transmit a digital 1, if it’s offyou transmit a 0,”Haas says, “They can be switched on and offvery quickly, which gives nice opportunities for transmitteddata.” It is possible to encode data in the light by varying therate at which the LEDs flicker on and off to give differentstrings of 1s and 0s.The LED intensity is modulated so rapidlythat human eye cannot notice, so the output appears constant. More sophisticated techniques could dramatically increaseVLC data rate. Terms at the University of Oxford and theUniversity of Edinburgh are focusing on parallel datatransmission using array of LEDs, where each LED transmits a different data stream. Other groups are using mixtures of red,green and blue LEDs to alter the light frequency encoding adifferent data channel. Li-Fi, as it has been dubbed, has alreadyachieved blisteringly high speed in the lab. Researchers at theHeinrich Hertz Institute in Berlin, Germany have reached datarates of over 500 megabytes per second using a standardwhite-light LED.
  • 7 System Design Li-Fi is typically implemented using white LED light bulbs at the downlink transmitter. These devices are normally used for illumination only by applying a constant current. However, by fast and subtle variations of the current, the optical output can be made to vary at extremely high speeds. This very property of optical current is used in Li-Fi setup.The operational procedure is very simple-,data from the internet and local network is used to modulate the intensity of the LED light source if any undetectable to the human eye. The photo detector picks up signal, which is converted back into a data stream and sent to the client. The client can communicate through its own LED output or over the existing network. An overhead lamp fitted with an LED with signal- processing technology streams data embedded in its beam at ultra-high speeds to the photo-detector. A receiver dongle then converts the tiny changes in amplitude into an electrical signal, which is then converted back into a data stream and transmitted to a computer or mobile device.
  • 8 Data Transmission Using LED
  • 9 Methods of Visible Light Communication Devices used for Visible Light Communication Communication using Image Sensors Devices used for Visible Light Communication Transmitter Device Receiver Device Methods of Visible Light Communication Transmitter device of visible light communication Visible Light LED LED light intensity is modulated by controlling its current. Data rate: low speed to very high speed (up to several hundred Mbps) Visible Light
  • 10 Visible Light LED Fluorescent Lamp FSK modulation of high frequency fluorescent light. Data rate: up to several kilo bps. Fluorescent Lamp Receiver device of visible light communication PIN photo diode: A PIN diode is a diode with a wide, lightly doped 'near' intrinsic semiconductor region between a p-type semiconductor and an n-type semiconductor region. The p-type and n-type regions are typically heavily doped because they are used for Ohmic contacts. The wide intrinsic region is in contrast to an ordinary PN diode. The wide intrinsic region makes the PIN diode an inferior rectifier (one typical function of a diode), but it makes the PIN diode suitable for
  • 11 attenuators, fast switches, photo detectors, and high voltage power electronics applications. Operation: A PIN diode operates under what is known as high-level injection. In other words, the intrinsic "i" region is flooded with charge carriers from the "p" and "n" regions. Its function can be likened to filling up a water bucket with a hole on the side. Once the water reaches the hole's level it will begin to pour out. Similarly, the diode will conduct current once the flooded electrons and holes reach an equilibrium point, where the number of electrons is equal to the number of holes in the intrinsic region. When the diode is forward biased, the injected carrier concentration is typically several orders of magnitude higher than the intrinsic level carrier concentration. Due to this high level injection, which in turn is due to the depletion process, the electric field extends deeply (almost the entire length) into the region. This electric field helps in speeding up of the transport of charge carriers from P to N region, which results in faster operation of the diode, making it a suitable device for high frequency operations.
  • 12 PIN photodiode Avalanche photo diode An avalanche photodiode (APD) is a highly sensitive semiconductor electronic device that exploits the photoelectric effect to convert light to electricity. APDs can be thought of as photo detectors that provide a built-in first stage of gain through avalanche multiplication. From a functional standpoint, they can be regarded as the semiconductor analog to photo multipliers.By applying a high reverse bias voltage (typically 100-200 V in silicon), APDs show an internal current gain effect (around 100) due to impact ionization (avalanche effect). However, some silicon APDs employ alternative doping and beveling techniques compared to traditional APDs that allow greater voltage to be applied (> 1500 V) before breakdown is reached and hence a greater operating gain (> 1000).In general, the higher the reverse voltage the higher the gain.
  • 13 Figure-2.6: Avalanche photo diode APD applicability and usefulness depends on many parameters. Two of the larger factors are: quantum efficiency, which indicates how well incident optical photons are absorbed and then used to generate primary charge carriers; and total leakage current, which is the sum of the dark current and photocurrent and noise. Electronic dark noise components are series and parallel noise. Series noise, which is the effect of shot noise, is basically proportional to the APD capacitance while the parallel noise is associated with the fluctuations of the APD bulk and surface dark currents. Another noise source is the excess noise factor, F. It describes the statistical noise that is inherent with the stochastic APD multiplication process. Image sensor An image sensor is a device that converts an optical image into an electronic signal. It is used mostly in digital cameras, camera modules and other imaging devices. Early analog sensors were video camera tubes; most currently used are digital charge-coupled
  • 14 device (CCD) or complementary metal–oxide–semiconductor (CMOS) active pixel sensors. Image sensor Communication using Image Sensors Principles of communication using image sensor
  • 15 Principles of Communication Using Image Sensor Camera (receiver) continuously takes images of a scene with an LED light and a receiver detects the optical intensity at a pixel where the LED light is focused on. Even if multiple visible light sources send data simultaneously, an image sensor is able to receive and demodulate all the data simultaneously without any interference between them. Merits of communication using image sensor Number of signal: Multiple. Robustness: no cross talk/no Interference. Distance: Very Long (2km). Space Resolution: Each pixel.
  • 16 Areas to which visible light communication technology may be applied Applications that do personal area communication. Applications that enable users to know users locations in several meter accuracy. Applications that enable users to know users locations in several millimeter accuracy. Applications that use augmented reality. Applications that cannot be achieved by radio-wave technology. Present Scenario We have 1.4million cellular mast radio waves base stations deployed. We also have over 5 billions of mobile phones. Mobile phone transmits more than 600 Tb of data. Wireless communication has become a utility like electricity & water. We use it in our everyday life, in our private life, business life. Currently Wi-Fi uses Radio Waves for communication. It is important to look into this technology which has become fundamental to our life.
  • 17 Four Issues with Radio Waves 1.Capacity: Radio waves are limited. Radio waves are scarce and expensive. We only have a certain range of it. With the advent of the new generation technologies like 2.5G, 3G, 4G and so on we are running out of spectrum. 2. Efficiency: There are 1.4 million cellular radio base stations. They consume massive amount of energy. Most of this energy is not used for transmission but for cooling down the base stations. Efficiency of such a base station is only 5%. 3. Availability: Availability of radio waves is another cause of concern. We have to switch off our mobiles in aero planes. It is not advisable to use mobiles at places like petrochemical plants and petrol pumps. 4. Security: Radio waves penetrate through walls. They can be intercepted.
  • 18 If someone has knowledge and bad intentions then he may misuse it. Alternative to Radio Waves in electromagnetic Spectrum There are four major concerns i.e., capacity, efficiency, availability and security related with Radio waves. But on the other hand we have 40 billions of light box already installed and light is the part of electromagnetic spectrum. Gamma rays are simply very dangerous and thus can’t be used for our purpose of communication. X-rays are good in hospitals and can’t be used either. Ultra-violet rays are good for getting a sun-tan but exposure for long duration is dangerous. Infrared rays are bad for our eyes and are therefore used at low power levels. We have already seen the shortcomings of Radio waves. So we are left with only Visible Light Spectrum.
  • 19 Also if we see the spectrum band of visible light than we will find that it is 10000 times more than that of radio waves.
  • 20 Light for Wireless Communication Light has been around for millions of years. It has created us created life and has created all stuffs of life. Visible light Communication (VLC) uses rapid pulses of light to transmit information wirelessly. Now it may be ready to compete with conventional Wi-Fi. So it is inherently safe to use for wireless communication. IMPLEMENTATION This brilliant idea was first showcased by Harald Haas from University of Edinburgh, UK, in his TED Global talk on VLC. He explained,” Very simple, if the LED is on, you transmit a digital 1, if it’s off you transmit a 0. The LEDs can be switched on and off very quickly, which gives nice opportunities for transmitting data.” So what you require at all are some LEDs and a controller that code data into those LEDs. We have to just vary the rate at which the LED’s flicker depending upon the data we want to encode. Further enhancements can be made in this method, like using an array of LEDs for parallel data transmission, or using mixtures of red, green and blue LEDs to alter the light’s frequency with each frequency encoding a different data channel. Such advancements promise a theoretical speed of 10Gbps– meaning you can download a full high-definition film in just 30
  • 21 seconds. Simply awesome! But blazingly fast data rates and depleting bandwidths worldwide are not the only reasons that give this technology an upper hand. Since Li-Fi uses just the light, it can be used safely in aircrafts and hospitals that are prone to interference from radio waves. This can even work underwater where Wi-Fi fails completely, thereby throwing open endless opportunities for military operations. Imagine only needing to hover under a street lamp to get public internet access, or downloading a movie from the lamp on your desk. There's a new technology on the block which could, quite literally as well as metaphorically, 'throw light on' how to meet the ever-increasing demand for high-speed wireless connectivity. Radio waves are replaced by light waves in a new method of data transmission which is being called Li-Fi. Light-emitting diodes can be switched on and off faster than the human eye can detect, causing the light source to appear to be on continuously. A flickering light can be incredibly annoying, but has turned out to have its upside, being precisely what makes it possible to use light for wireless data transmission. Light-emitting diodes (commonly referred to as LEDs and found in traffic and street lights, car brake lights, remote control units and countless other applications) can be switched on and off faster than the human eye can detect, causing the light source to appear to be on continuously, even though it is in fact 'flickering'. This invisible on-off activity enables a kind of data transmission using binary codes: switching on an LED is a logical '1',
  • 22 switching it off is a logical '0'. Information can therefore be encoded in the light by varying the rate at which the LEDs flicker on and off to give different strings of 1s and 0s. This method of using rapid pulses of light to transmit information wirelessly is technically referred to as Visible Light Communication (VLC), though it’s potential to compete with conventional Wi-Fi has inspired the popular characterization Li-Fi. Visible light communication “A potentialsolution 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. The main components of this communication system are a high brightness white LED, Which acts as a communication source and a silicon photodiode which shows good response to visible wavelength region serving as the receiving element. LED can be switched on and off to generate digital strings of 1s and 0s.
  • 23 Data can be encoded in the light to generate a new data stream by varying the flickering rate of the LED. To be clearer, by modulating the LED light with the data signal, the LED illumination can be used as a communication source. As the flickering rate is so fast, the LED output appears constant to the human eye. A data rate of greater than 100 Mbps is possible by using high speed LEDs with appropriate multiplexing techniques. VLC data rate can be increased by parallel data transmission using LED arrays where each LED transmits a different data stream. There are reasons to prefer LED as the light source in VLC while a lot of other illumination devices like fluorescent lamp, incandescent bulb etc. are available. COMPARISION BETWEEN Li-Fi & Wi-Fi LI-FI is a term of one used to describe visible light communication technology applied to high speed wireless communication. It acquired this name due to the similarity to WI-FI, only using light instead of radio. Wi-Fi is great for general wireless coverage within buildings, and Li-Fi is ideal for high density wireless data coverage in confined area and for relieving radio interference issues, so the two technologies can be considered complimentary.
  • 24 Technology Speed Data density Wireless (current) Wi-Fi – IEEE 802.11n 150 Mbps * Bluetooth 3 Mbps ** IrDA 4 Mbps *** Wireless (future) WiGig 2 Gbps ** Giga-IR 1 Gbps *** Li-Fi >1Gbps >1Gbps **** Comparison between current and future wireless technology The table also contains the current wireless technologies that can be used for transferring data between devices today, i.e. Wi-Fi, Bluetooth and IrDA. Only Wi-Fi currently offers very high data rates. The IEEE 802.11.n in most implementations provides up to 150Mbit/s (in theory the standard can go to 600Mbit/s) although in practice you receive considerably less than this. Note that one out of three of these is an optical technology. How it is different? Li-Fi technology is based on LEDs for the transfer of data. The transfer of the data can be with the help of all kinds of light, no matter the part of the spectrum that they belong. That is, the light can belong to the invisible, ultraviolet or the visible part of the spectrum. Also, the speed of the internet isincredibly high and you can download movies, games, music etc in just a few minutes with the help of this technology.
  • 25 Also, the technology removes limitations that have been put on the user by the Wi-Fi. You no more need to be in a region that is Wi-Fi enabled to have access to the internet. You can simply stand under any form of light and surf the internet as the connection is made in case of any light presence. There cannot be anything better than this technology. What we have to do? We have to replace inefficient fluorescents with this new dignitary of LED lights. The LED will hold a micro-chip that will do the job of processing the data. Light intensity can be modulated at very high speeds to send data by tiny changes in amplitude.
  • 26 Achieving Communication through Light Let’s start with the foremost communication device which everyone has in their homes i.e., a Remote Control. A remote control has an Infrared-LED. It creates a single data stream and the data rate achieved is around 10000b/s to 20000b/s. Now if we replace the remote control with a light box, we are able to transmit 1000’s of data stream in parallel at high speeds. This technology is termed as Spatial Modulation. Remote Control Data via LED Is it a Proven Technology? Yes, this is already proven. Harald Haas demonstrated his invention using an ordinary table lamp that successfully transmitted data at speeds exceeding 10Mbps using light waves from LED light bulbs to a computer located below the lamp. To prove that the light bulb was the source of the data stream, he periodically blocked the beam of light, causing the connection to drop.
  • 27 Overcoming the four issues with RW in Li-Fi 1.Capacity: 10000 times more spectrum than RW. LEDs are already present. So we have the infrastructure available and already installed. 2.Efficiency: Data through illumination and thus data transmission comes for free. LED light consumes less energy Highly efficient 3.Availability Light is present everywhere. 4.Security: Light waves don’t penetrate through walls. Data is present where there is light.
  • 28 Applications of Li-Fi At present its applications are beyond imagination but still if to think about few then they are: Can be used in places where it is difficult to lay the optical fiber like hospitals. In operation theatre Li-Fi can be used for modern medical instruments. In traffic signals Li-Fi can be used which will communicate with LED lights of the cars and accident numbers can be decreased. Thousand and millions of street lamps can be transferred to Li-Fi Lamps to transfer data. In aircraft Li-Fi can be used for data transmission. It can be used in petroleum or chemical plants where other transmission or frequencies could be hazardous.
  • 29 Conclusion he possibilities are numerous and can be explored further. If this technology can be put into practical use, every bulb can beused something like a Wi-Fi hotspot to transmit wireless dataand we will proceed toward the cleaner, greener, safer andbrighter future. The concept of Li-Fi is currently attracting agreat deal of interest, not least because it may offer a genuineand very efficient alternative to radio- based wireless. As agrowing number of people and their many devices accesswireless internet, the airwaves are becoming increasinglyclogged, making it more and more difficult to get a reliable,high-speed signal. This may solve issues such as the shortageof radio-frequency bandwidth and also allow internet wheretraditional radio based wireless isn’t allowed such as aircraftor hospitals. One of the shortcomings however is that it onlywork in direct line of sight. T
  • 30 References http://en.wikipedia.org/wiki/Li-Fi http://teleinfobd.blogspot.in/2012/01/what-is-lifi.html www.lificonsortium.org/ Will Li-Fi be the new Wi-Fi?, New Scientist, byJamieCondliffe, dated 28 July 2011 http://www.digplanet.com/wiki/Li-Fi “Visible-light communication: Tripping the lightfantastic: A fast and cheap optical version of Wi-Fi iscoming”, Economist, dated 28Jan 201