2/13/2015 LiFiGetsReadytoCompeteWithWiFiIEEESpectrum

http://spectrum.ieee.org/telecom/internet/lifigetsreadytocompetewithwifi 1/3

Li-Fi Gets Ready to Compete With Wi-Fi

VisiblelightcommunicationscouldoutshineWiFiinindustrialsettings

ByNeilSavagePosted20Nov2014|16:00GMT

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Photo:PeterTuffy/TheUniversityofEdinburgh

ACMOSdigitaltoanalogconverterdevelopedattheUniversityofEdinburghhelpsLEDsactascommunicationsdevices.LightFantastic:

AsLEDsbecomeamorecommonsourceforroom,

theyreopeninganewpathwayforlinkingmobiledevicestotheInternet,withthepotentialforwiderbandwidthandquickerresponsetimethan

.Atleastthatswhatresearcherssuchas ,chairofmobilecommunicationsattheUniversityofEdinburgh,arehoping.

lighting(file:///Users/evrielin/Documents/K4%20Data%206/PlacedObjects/spectrum.ieee.org/tag/LED+lighting)

WiFi(file:///Users/evrielin/Documents/K4%20Data%206/PlacedObjects/spectrum.ieee.org/tag/WiFi)

HaraldHaas(http://www.see.ed.ac.uk/drupal/hxh)

Allthecomponents,allthemechanismsexistalready,Haassays.Youjusthavetoputthemtogetherandmakethemwork.

2/13/2015 LiFiGetsReadytoCompeteWithWiFiIEEESpectrum

http://spectrum.ieee.org/telecom/internet/lifigetsreadytocompetewithwifi 2/3

,alongwithresearchersfromtheUniversitiesofCambridge,Oxford,St.Andrews,andStrathclyde,arehalfwaythroughafouryear,5.8millionprojectfundedbytheEngineeringandPhysicalSciencesResearchCouncil,intheUnitedKingdom.Theyarepursuing ,whichwouldusemultiplecolorsoflighttoprovidehighbandwidthlinkagesoverdistancesofafewmeters.SuchaLiFisystem,asitsbeendubbed,couldsupplementorinsomeinstancesreplacetraditionalradiobasedWiFi,theysay.Buttakingonsuchabroadlyusedradiotechnologyisanuphillbattle.

Haassgroup(http://www.see.ed.ac.uk/drupal/hxh/about/)

ultraparallelvisiblelightcommunication(http://upvlc.photonics.ac.uk/)

Atthe ,membersoftheconsortiumshowedofftheprogresstheyremaking.Forinstance,theteamhasusedcommerciallyavailablered,green,andblueLEDsasbothemittersandasphotodiodestodetectlight.Bydoingthat,theycreatedasystemthatcouldbothsendandreceivedataataggregateratesof110megabitspersecond.Whentransmittinginonedirectiononly,theyreachedarateof155Mb/s.

IEEEPhotonicsConferenceinOctober(http://www.ipcieee.org/)

ButHaassaysthatthisversionislimitedbyexistingLEDs,andbytheuseofLEDsastransmittersanddetectorsatthesametime.Membersoftheconsortium,however,havecreatedabetterLED,whichprovidesadataratecloseto4gigabitspersecondoperatingonjust5milliwattsofopticaloutputpowerandusinghighbandwidthphotodiodesatthereceiver.Withasimplelenstoenhancethedistance,theycansenddata10metersatupto1.1Gb/s,andsoontheywillincreasethatto15Gb/s,Haassays.The802.11adWiFistandardforthe60gigahertzradiobandreachesjustunder7Gb/s,soLiFiwouldmorethandoublethatrate.

Theyrealsousingavalanchephotodiodestomakebetterreceivers.Inanavalanchephotodiode,asinglephotonstrikingthereceiverproducesacascadeofelectrons,amplifyingthesignal.HaassteamattheLiFiR&DCentrehascreatedthefirstreceiverchipforLiFiwithintegratedavalanchephotodiodesonCMOS.The7.8squaremillimeterIChouses49photodiodes.

Separately,the ,inDresden,Germany,hadannouncedplansto

inNovember(afterpresstime)attheElectronica2014tradeshowinMunich.FrankDeicke,wholeadstheteamdevelopingLiFiatFraunhofer,saysthatthesystemwouldmostlikelyuseinfraredlightandisaimedatindustrialusersratherthanconsumers.Thehotspotwassettobeapointtopointlinkwithadatarateofupto1Gb/s.

FraunhoferInstituteforPhotonicMicrosystems(http://www.ipms.fraunhofer.de/en.html)demonstrateaLiFihotspot

(http://www.ipms.fraunhofer.de/en/applications/wirelesssystems/irda.html)

YoucanhavemoreorlessthesamedatarateasoveraUSBcable,Deickesays.Thatsverychallengingformostwirelesstechnologies,likeWiFiandBluetooth.Anotheradvantage,saysDeicke,isthatthelatencyofWiFithetimebetweenwhenasignalissentandwhenitsreceivedismeasuredinmilliseconds,whereasLiFislatencyisontheorderofmicroseconds.Inindustrialapplications,wheredatahastoflowbetweensensors,actuators,andacontrolunit,lowlatencyandhighdatarateswouldmakeLiFiusefulinplaceswhereWiFiisnot.WedontwanttoreplaceWiFi,hesays.Thatsnotourgoal.

ButDeickesaysLiFicouldcomplementexistingcommunicationstechnologies,includingWiFiandgigabitEthernet.Fornow,hisgroupisnotfocusingoncombiningitwithgenerallighting,asHaasproposes.

AgroupofEuropeanacademicresearchersandnetworkingcompaniesisaimingfortheconsumermarket,though.ThegroupisworkingonaprojectcalledAdvancedConvergentandEasilyManageableInnovativeNetworkDesign(ACEMIND)(http://celticplus.eu/Projects/CelticPlusProjects/2012/ACEMIND/acemind

2/13/2015 LiFiGetsReadytoCompeteWithWiFiIEEESpectrum

http://spectrum.ieee.org/telecom/internet/lifigetsreadytocompetewithwifi 3/3

todevelopwaystomanagelocalnetworksinhomesandsmallbusinesses.ACEMINDincludesanumberofdemonstratorprojectstotestdifferenttechnologies,includingLiFi.

,whoisaparticipantinACEMIND,thinksLiFimightbeinpracticalusewithinthenextfiveyears.LiFihastheadvantageofbeingusefulinelectromagneticallysensitiveareassuchasinhospitals,aircraftcabins,andpowerplants,hesays.

default.asp)DmitrisKatsianisatthe

UniversityofAthens(http://www.di.uoa.gr/)

Haasiscountingonamuchbiggermarket.HeexpectsLEDstoevolvepastjustbeinglightsources,muchthesamewaythecellphoneevolvedfromacommunicationsdevicetoamobilecomputer.In25years,everylightbulbinyourhousewillhavetheprocessingpowerofyourcellphonetoday,hesays.Itwillinthefutureserveilluminationasjustoneofmanypurposes.

AbouttheAuthor

,basedinLowell,Mass.,writesaboutstrangesemiconductors,unusualoptoelectronics,andotherthings.IntheMay2014issuehereportedon

.

NeilSavage(http://www.neilsavage.com/)weirdwaystomakethings

invisible(http://spectrum.ieee.org/semiconductors/materials/threeweirdwaystomakethingsinvisible)

Acorrectiontothisarticlewasmadeon20November2014.