Li-Fi
LiFi works in complement with existing and emerging wireless systems.Light Fidelity(Li-Fi) is abidirectional, high-speed and fully networkedwireless communicationtechnology similar toWi-Fi.
The term was coined byHarald Haas[1]and is a form ofvisible light communicationand a subset ofoptical wireless communications(OWC) and could be a complement toRF communication(Wi-Fi orcellular networks), or even a replacement in contexts ofdata broadcasting.
It is wire and uv visible-light communication orinfraredandnear-ultravioletinstead ofradio-frequencyspectrum, part of optical wireless communications technology, which carries much more information and has been proposed as a solution to theRF-bandwidth limitations.
[2]Technology detailsThis OWC technology uses light fromlight-emitting diodes(LEDs) as a medium to deliver networked, mobile, high-speed communication in a similar manner toWi-Fi
.[3]The Li-Fi market is projected to have acompound annual growth rateof 82% from 2013 to 2018 and to be worth over $6 billion per year by 2018
.[4]Visible light communications(VLC) works by switching the current to the LEDs off and on at a very high rate,
[5]too quick to be noticed by the human eye. Although Li-Fi LEDs would have to be kept on to transmit data, they could be dimmed to below human visibility while still emitting enough light to carry data.
[6]The light waves cannot penetrate walls which makes a much shorter range, though moresecure from hacking, relative to Wi-Fi.[7]
[8]Direct line of sight is not necessary for Li-Fi to transmit a signal; light reflected off the walls can achieve 70Mbit/s.
[10]Li-Fi has the advantage of being useful in electromagnetic sensitive areas such as inaircraft cabins, hospitals and nuclear power plants without causingelectromagnetic interference.[7][11]
[8]BothWi-Fi and Li-Fi transmit data over theelectromagnetic spectrum, but whereas Wi-Fi utilizes radio waves, Li-Fi uses visiblelight. While the US Federal Communications Commission has warned of a potential spectrum crisis because Wi-Fi is close to full capacity, Li-Fi has almost no limitations on capacity
.[12]The visible light spectrum is 10,000 times larger than the entireradio frequencyspectrum.[13]Researchers have reached data rates of over224 Gbit/s, which is much faster than typical fastbroadbandin2013.[14][15]Li-Fi is expected to be ten times cheaper than Wi-Fi.[6]Short range, low reliability and high installation costs are the potential downsides.[4]
[5]PureLiFidemonstrated the first commercially available Li-Fi system, the Li-1st, at the 2014Mobile World Congressin Barcelona.[16]Bg-Fi is a Li-Fi system consisting of an application for a mobile device, and a simple consumer product, like an IoT (Internet of Things) device, with color sensor, microcontroller, and embedded software. Light from the mobile device display communicates to the color sensor on the consumer product, which converts the light into digital information. Light emitting diodes enable the consumer product to communicate synchronously with the mobile device.[17]
[18]HistoryHarald Haas, coined the term "Li-Fi" at his TED Global Talk where he introduced the idea of "Wireless data from every light".
[19]He is Chairman of Mobile Communicationsat theUniversity of Edinburghand co-founder of pureLiFi.[20]The general termvisible light communication(VLC), whose history datesback to the 1880s, includes any use of the visible light portion of the electromagnetic spectrum to transmit information. The D-Light project at Edinburgh's Institute for Digital Communications was funded from January 2010 to January 2012.
[21]Haas promoted this technology in his 2011TED Globaltalk and helped start a company to market it.[22]PureLiFi, formerly pureVLC, isanoriginal equipment manufacturer(OEM)firm set up to commercialize Li-Fi productsfor integration with existingLED-lighting systems.[23]
[24]In October 2011, companies and industry groups formed theLi-Fi Consortium, to promote high-speed optical wireless systems and to overcome the limited amount of radio-based wireless spectrum available by exploiting a completely different part of the electromagnetic spectrum.[25]A number of companies offer uni-directional VLC products, which is not the same as Li-Fi - a term defined by the IEEE 802.15.7r1 standardization committee
.[26]VLC technology was exhibited in 2012 using Li-Fi.[27]By August 2013, data rates of over 1.6 Gbit/s were demonstrated over a single color LED.[28]In September 2013, a press release said that Li-Fi, or VLC systems in general, do not require line-of-sight conditions.[29]In October 2013, it was reported Chinese manufacturers were working on Li-Fi development kits.
[30]In April 2014, the Russian company Stins Coman announced the development of a Li-Fi wireless local network called BeamCaster. Their current module transfers data at 1.25 gigabytes per second but they foresee boosting speeds up to 5 GB/second in the near future.[31]In2014 a new record was established by Sisoft (a Mexican company) that was able to transfer data at speeds of up to 10 Gbit/s across a light spectrum emitted by LED lamps.
[32]Recent integratedCMOSoptical receivers for Li-Fi systems are implemented withavalanche photodiodes(APDs) which has a low sensitivity.[33]In July 2015,IEEEhasoperated the APD inGeiger-modeas asingle photon avalanche diode(SPAD) to increase the efficiency of energy-usage and makes the receiver more sensitive.[34]Also this operation could be performed asquantum-limitedsensitivity that makes receivers detect weak signals from far distance.
[33]StandardsLike Wi-Fi, Li-Fi is wireless and usessimilar802.11 protocols; but it usesvisible light communication(instead of radio frequency waves), which has much widerbandwidth.One part of VLC is modeled after communication protocols established by theIEEE802 workgroup. However, theIEEE802.15.7standard is out-of-date, it fails to consider the latest technological developments in the field of optical wireless communications, specifically withthe introduction of opticalorthogonal frequency-division multiplexing(O-OFDM) modulation methods which have been optimized for data rates, multiple-access and energy efficiency.
[35]The introductionof O-OFDM means that a new drive for standardization of optical wireless communications is required.Nonetheless, the IEEE 802.15.7 standard defines thephysical layer(PHY) andmediaaccess control(MAC) layer. The standard is able to deliver enough data rates to transmit audio, video and multimedia services. It takes into account optical transmission mobility, its compatibility with artificial lighting present in infrastructures, and the interference whichmay be generated by ambient lighting.
TheMAC layer permits using the link with the other layers as with theTCP/IPprotocol.[citation needed]
The standard defines three PHY layers with different rates:*.The PHY 1 was established for outdoor application and works from 11.67 kbit/s to 267.6 kbit/s.*.The PHY 2 layer permits reaching data rates from 1.25 Mbit/s to 96 Mbit/s.*.The PHY 3 is used for many emissions sources with a particular modulation method called color shift keying (CSK). PHY III can deliver rates from 12 Mbit/s to 96 Mbit/s.[36]The modulation formats recognized for PHY I and PHY II areon-off keying(OOK) and variablepulse position modulation(VPPM). TheManchester codingused for the PHY I and PHY II layers includes the clock inside the transmitted data by representing a logic 0 with an OOK symbol"01" and a logic 1 with an OOK symbol "10",all with a DC component. The DC component avoids light extinction in case of an extended run of logic 0's.[citation needed]The first VLCsmartphoneprototype was presented at theConsumer Electronics Showin Las Vegas from January 7–10 in 2014. The phone uses SunPartner's Wysips CONNECT, a technique that converts light waves into usable energy, making the phone capable of receiving and decoding signals without drawing on its battery.[37][38]A clear thin layer of crystal glass can be added to small screens like watches and smartphones that make them solar powered. Smartphones could gain 15% more battery life during a typical day. This first smartphones using this technology should arrive in 2015. This screen can alsoreceive VLC signals as well as the smartphone camera.[39]The cost of these screens per smartphone is between $2 and $3, much cheaper than most new technology.[40]Philipslighting company has developed a VLC system for shoppers at stores. They have to download an app on their smartphone and then their smartphone works with the LEDs in the store. The LEDscan pinpoint where they are located in the store and give them corresponding coupons and information based on which aisle they are on and what they are lookingat.[41]Home & Building AutomationIt is predicted that future home & building automation[42]will be highly dependent on the Li-Fi technology for being secure & fast. As the light cannot penetrate throughwalls hence the signal cannot be hacked from a remote location.ApplicationsSecurityIn contrast toradio frequency wavesused by Wi-Fi, lights cannot penetrate through walls and doors. In a meeting or living room condition, with some prevention ontransparent materials, like curtains on window, the access of a Li-Fi channel is constrained in that room.[43]Underwater ApplicationMostremotely underwater operated vehicles(ROVs) use cables to transmit command, but the length of cables then limits the area ROVs can detect. However, aslight wavecould travel through water, Li-Fi could be implemented on vehicles to receive and send back signals.[44]HospitalMany treatments now involve multiple individuals, Li-Fi system could be a better system to transmit communication about the information of patients.[45]Besides providing a higher speed, light waves also have little effect onmedical instrumentsand human bodies.[46]VehiclesVehiclescould communicate with one another via front and back lights to increase road safety. Also street lamps and traffic signals could also provide information about current road situations.[47]See also*.Bluetooth*.Free-space optical communication*.Infrared communication*.IrDA*.Near Field Communication(NFC)*.Spatial light modulator(SLM)*.Super Wi-FiReferences1.^Harald Haas."Harald Haas: Wireless data from every light bulb".ted.com.2.^Tsonev, Dobroslav; Videv, Stefan; Haas,Harald (December 18, 2013). "Light fidelity (Li-Fi): towards all-optical networking".Proc. SPIE. Broadband Access Communication Technologies VIII.9007(2).doi:10.1117/12.2044649.3.^Sherman, Joshua (30 October 2013)."How LED Light Bulbs could replace Wi-Fi".Digital Trends. Retrieved29 November2015.4.^ab"Global Visible Light Communication (VLC)/Li-Fi Technology Market worth$6,138.02 Million by 2018". MarketsandMarkets. 10 January 2013. Retrieved29 November2015.5.^abCoetzee, Jacques (13 January 2013)."LiFi beats Wi-Fi with 1Gb wireless speeds over pulsing LEDs".Gearburn. Retrieved29 November2015.6.^abCondliffe, Jamie (28 July 2011)."Will Li-Fi be the new Wi-Fi?".New Scientist.7.^abLi-Fi – Internet at the Speed of Light, byIan Lim, the gadgeteer, dated 29 August 20118.^ab"Visible-light communication: Tripping the light fantastic: A fast and cheap optical version of Wi-Fi is coming".The Economist. 28 January 2012. Retrieved22 October2013.9.^"The internet on beams of LED light".The Science Show. 7 December 2013.10.^"PureLiFi aims at combating cyber crime".Ads Advance.11.^"Li-Fi: A green avatar of Wi-Fi".Livemint. 9 January 2016. Retrieved24 February2016.12.^"The Future's Bright - The Future's Li-Fi".The Caledonian Mercury. 29 November 2013. Retrieved29 November2015.13.^Haas, Harald (19 April 2013). "High-speed wireless networking using visiblelight".SPIE Newsroom.doi:10.1117/2.1201304.004773.14.^Vincent, James (29 October 2013)."Li-Fi revolution: internet connections using light bulbs are 250 times".The Independent. Retrieved29 November2015.15.^"'Li-fi' via LED light bulb data speed breakthrough".BBC News. 28 October 2013. Retrieved29 November2015.16.^"pureLiFi to demonstrate first ever Li-Fi system at Mobile World Congress". Virtual-Strategy Magazine. 19 February 2014. Retrieved29 November2015.17.^Giustiniano, Domenico; Tippenhauer, Nils Ole; Mangold, Stefan."Low-Complexity Visible Light Networking with LED-to-LED Communication"(PDF). Zurich, Switzerland.18.^Dietz, Paul; Yerazunis, William; Leigh, Darren (July 2003)."Very Low-Cost Sensing and Communication Using Bidirectional LEDs"(PDF).19.^https://www.ted.com/talks/harald_haas_wireless_data_from_every_light_bulb?language=en20.^https://www.crunchbase.com/organization/purelifi#/entity21.^Povey,, Gordon."About Visible Light Communications". pureVLC. Archived fromthe originalon 18 August 2013. Retrieved22 October2013.22.^Haas, Harald (July 2011)."Wireless data from every light bulb".TED Global.Edinburgh,Scotland.23.^"pureLiFi Ltd". pureLiFi. Retrieved22December2013.24.^"pureVLC Ltd".Enterprise showcase. University of Edinburgh. Retrieved22 October20
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