LIFITECHNOLOGYINWIRELESSCOMMUNICATION

GIRIRAJKR.PATIDAR

1DepartmentofElectronics&CommunicationEngineering,AryaInstituteofEngineering&Technology,Kukas,Jaipur,Rajasthan,India

Email:giriraj211@gmail.comABSTRACT

LIFIisabroadcastofinformationduringlighting,transferinformationthroughaLEDlightbulbthatintensityvariesquickerthan human eye can track.Whether you are bymeans ofwireless internet in a coffee house, thieving it from the guysubsequentlydoor,orparticipating forbandwidthata convention, youhavealmost certainlygotten irritatedat the slowspeedyoufacewhenmorethanoneapparatusistappedaddictedtotheassociation.Asmoreandmorepublicandtheirmanydevicesaccesswirelessinternet,stoppedupairwavesaredepartingtomakeitonegermenphysicistHeraldHaashascomeupwithawayouthecallsdataandinformationthroughoutlightingtakingthefibberoutoffibreopticbytransferdataandinformationallthewaythroughanLED lightbulbthatvaries in intensityquicklythanthehumanbeingeyecangobehindthatvariesinintensityfasterthanthehumaneyecangobehind.LIGHT,cangeneratedata&informationratesmorerapidlythan 10megabits per second,which is faster than your average broadband link.He envisionsa outlookwhere data andinformationfortablets,smartphones,andlaptopsisinheritedthroughthelightinanarea.Andsafetywouldbesnapifyoucan`tseethelight,youcan`taccesstheinformation.

Keywords:LED,VLC,WiFi,LiFi1. INTRODUCTION

Transferofdatafromoneplacetoadifferentplaceisoneof the most important daytoday manners. The currentwireless networks that attach us to the internet areextremelyslowwhennumerousdevicesareconnected.Asthe amount of devices that access the internet increases,the fixed bandwidth accessible makes it extra and extratricky to enjoy high data transfer rates and attach to asecurenetwork.But,radiowavesarejustaminutepartofthebandavailablefordatatransfer.AsolutiontothistroubleisbytheuseofLiFi,LiFistandsfor LightFidelity. LiFi is the broadcast of data throughlightbytakingthefibreoutoffibreopticsbytransferdatathrough an LED light bulb that varies in intensity morerapidly than the human eye can follow. LiFi is thewordsomehaveused to label the fastandeconomicalwirelesscommunicationorganism,whichistheopticaldescriptionofWiFi. LiFi uses observable light instead of Gigahertzradioraysfordatatransmit.

Figure1:LiFiBulb

ThetermwasprimaryusedinthiscircumstancebyHaraldHaas in his TED worldwide talk on perceptible Lightproclamation. At theunderstandingof courageofhigherintensityof lightemittingdiodesbythisnewtechniques,said by Harald Haas in, UK, Very cleanly, if the LightEmittingDiodeison,youbroadcastadigital1,ifitsoffyoubroadcasta0,Haassays,Theycanbeswitchedonandoffvery rapidly, which gives nice opportunity for transmitdataand information.That isattainable toprospectus intwist in the light by changing the rate atwhich the LEDsflickeronandoffforsendalteredstringsof1sand0s.TheLEDintensitymodulatedveryfastthathumaneyecannotnotice, so theoutputappears constant.More complicatedtechniques could dramatically increase VLC data andinformationrate.TermsattheUniversityofOxfordandtheUniversity of Edinburgh are focusing on parallelinformationanddatabroadcastthroughcollectionofLEDs,where each LED transmits a dissimilar data flow. Otherfaction is using mixtures of green, blue and red colourLEDs tomodify the light frequency encoding a dissimilarinformation path. LiFi, as it has been twice, has alreadyachieved blisteringly high speed in the lab. PhD researchscholarattheHeinrichHertzInstituteinBerlin,Germany,have reach information rates of over 500megabytes persecond using a standardwhitelight LED. The technologywasestablishedatthe2012ConsumerElectronicsShowinLasVegasusingapairofCasiosmartphonestoswapoverdata using light of altering intensity given off from theirscreens,visibleatadistanceofuptotenmetres.Fig.1LiFienvironmentInOctober2011anumberofcompaniesandindustrygroups formed theLiFiConsortium, topromotehighspeedwirelesscommunicationsystemsandtodefeatthe limited amount of radio based wireless spectrumaccessiblebyexploitingaabsolutelydissimilarpartoftheelectromagnetic spectrum.The consortiumsconsider it ispossible toachievemore than10Gbps, in theoryallowahighdescriptionfilmtobedownloadedin30seconds.

GIRIRAJ KR. PATIDAR et al. DATE OF PUBLICATION: DEC 18, 2014

ISSN: 2348-4098 VOL 2 ISSUE 8 NOV-DEC 2014

INTERNATIONAL JOURNAL OF SCIENCE, ENGINEERING AND TECHNOLOGY- www.ijset.in 126

2. STRUCTUREOFLIFIORGANISM

LiFiisahighspeedandeconomicalopticalversionofWiFi.ItisbasedonVisibleLightCommunication(VLC).VLCisa data communication channel, which uses perceptiblelightbetween400THz(780nm)and800THz(375nm)asoptical carrier for data & information broadcast andillumination. It uses rapid pulse of light to broadcastinformation&datawirelessly.ThemaincomponentsofLiFisystemareasfollows:a)AhighbrightnesswhiteLEDwhichactsastransmissionsource.b) A photodiode of siliconwith good response to visiblelightasthereceivingelement.LEDscanbeswitchedonandofftogeneratedigitalstringsof dissimilar arrangement of 1 & 0. To produce a newinformationflow,datacanbeprogrammedinthelightbychangingthesparklingrateoftheLED.

Figure2:DatatransferviaLiFi

TheLEDscanbewornasadispatcherorsource,withthehelp ofmodulating the LED light by the data signal. TheLEDproductivityappearstabletothehumaneyebyassetof the fast flickeringrateof theLED.Communicationrategreater than 100 Mbps is possible by using high speedLEDs with the facilitate of a variety of multiplexingtechniques. VLC rate of information can be improved byparalleldatacommunicationusinganarrayofLEDswhereeach LED transmits a different data stream. The LiFiemittersystemconsistsof4primarysubassemblies[10]:a)Bulbb)RFpoweramplifiercircuit(PA)c)Printedcircuitboard(PCB)d)EnclosureThePCB controls the electrical inputs andoutputs of thelamp and houses the microcontroller used to managedifferent lamp functions.ARF (radiofrequency) signal isgenerated by the solidstate PA and is guided into anelectric field about the bulb. The high engrossment ofenergy in the electric field vaporizes the contents of thebulb toaplasmastateat thebulb`scentre thiscontrolledplasma generates an intense source of light. All of thesesubassemblies (shown in Fig. 2) are contained in an

aluminium enclosure [10]. The bulb subassembly is theheartoftheLiFiemitter.Itconsistsofasealedbulbwhichisembeddedinadielectricmaterial.This intends ismorereliable than conventional light sources that insertdegradable electrodes into the bulb [3]. The dielectricmaterial serves two purposes. It acts as awaveguide forthe RF energy transmitted by the PA. It also acts as anelectricfieldconcentratorthatfocusesenergyinthebulb.Theelectric fieldrapidlyheatsandproduceenergytothematerial in the bulb to a plasma state that emits light ofhigh intensityand full spectrum [10]. Figure3 shows thebulbsubassembly.

Figure3:DatatransmissionusingLED

There are various inherent advantages of this approachwhich includes high brightness, excellent colour qualityand high luminous efficacy of the emitter in the range of150 lumens per watt or greater. The structure ismechanically robust without typical degradation andfailure mechanisms associated with glass and tungstenelectrodestometalseal,resultinginconstructivelamplifeof 30,000+ hours. In addition, the unique combination ofhigh temperature plasma and digitally controlled solidstate electronics results in an economically producedfamily of lamps scalable in packages from 3,000 to over100,000lumens[2].3. FUNCTIONINGOFLIFI

Anewgenerationofhighbrightness lightemittingdiodesformsthecorepartoflightfidelitytechnology.Thelogicisvery simple. If the LED is turn on, a digital pulse 1 istransmitted. If the LED is turnoff, a digital pulse 0 istransmitted.ThesehighbrightnessLEDs canbe switchedon and off very quickly which gives us a very niceopportunitiesfortransmittingdatathroughlight[12].Theworking of LiFi is very simple. Therefore light emits ononeend, forexample,anLED,andaphotodetector(lightsensor) on the other end. The photo detector registers abinary1whentheLEDisonandabinary0iftheLEDisoff.Tomakeupamemorandum,flashtheLEDfrequenttimesoruseanarrayofLEDsofperhapsafewdifferentcolours,toobtaininformationintherangeofhundredsofmegabitspersecond.

GIRIRAJ KR. PATIDAR et al. DATE OF PUBLICATION: DEC 18, 2014

ISSN: 2348-4098 VOL 2 ISSUE 8 NOV-DEC 2014

INTERNATIONAL JOURNAL OF SCIENCE, ENGINEERING AND TECHNOLOGY- www.ijset.in 127

Figure4:BlockdiagramofLiFisystem

TheblockdiagramofLiFisystemisshown inFig.4.Thedatacanbeencoded in the lightbyvarying the flickeringrate at which the LEDs flicker on and off to generatedissimilarstringof1s&0s.TheLEDintensityismodulatedsorapidlythathumaneyecannotnotice it,sothe lightoftheLEDappearsconstanttohumans[13].Lightemittingdiodes(commonlyreferredtoasLEDsandfound in traffic and street lights, car put on the brakeslights, remote control part and countless otherapplications) can be switched on and off faster than thehuman eye can detect, foundation the light source toappear to be on continuously, even though it is in fact'flickering'.Theonoffmovementof thebulbwhich looksto be invisible enables data transmission using binarycodes:switchingonanLEDisalogical '1',switchingitoffisalogical'0'.ByvaryingtherateatwhichtheLEDsflickeron and off, information can be encoded in the light todissimilarpermutationof1s&0s.This type techniqueofusing rapid pulses of light to transmit informationwirelessly is technically referred to as Visible LightCommunication(VLC),thoughitispopularlycalledasLiFibecause it can compete with its radiobased rival WiFi.Figure 5 shows a LiFi system connecting devices in aroom.Manyothersophisticatedtechniquescanbeusedtodramatically increase VLC data rate. Teams at theUniversity ofOxford and theUniversity of EdinburgharefocusingonparalleldatatransmissionusingarrayofLEDs,whereeachLEDbroadcastadissimilardatastream.Othergroupsareusin