الفهرس 
IntroductiontoVisibleLight CommunicationsOnly 14 pages are availabe for public view
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Abstract
Visiblelightcommunication(VLC)offersgreaterbandwidththanradiofrequency(RF).Ac- cordingly,itisbeinginvestigatedforadoptionintheupcomingsixth-generation(6G)systems. Thanks tolight-emittingdiodes(LEDs),weareabletohaveluminairesthatarecapableofdata transmission withoutaffectingthesurroundingenvironmentortheirfunctionality.Accordingly, commercial high-efficiencyLEDsareexpectedtobeintensivelyusedincommunicationsas theyoffercheap,non-complex,unlicensedfrequencyband,safe,andsecuresolutionforboth illumination anddatatransmission.Itisalsousedwithmanytechnologiesinhybridapplica- tions suchasindoorpositioningsystems(IPS),machine-to-machine(M2M)communications, augmented reality,smartcitiesandnon-RFfriendlyenvironments. Although VLCwasintensivelystudiedthroughthepastyears,therearestillchallengesthat limit highdataratestransmissionduetoLEDslimitationssuchasphosphorlongphotolumines- cence lifetimes,smallmodulationbandwidthandnonlinearity.Thelowmodulationbandwidth of commercialwhiteLEDsisabottleneckinhigh-speedVLCsystems.Thisisduetothephys- ical mechanismsintheLEDquantumwell.Thelimitedbandwidth(fewMHz)dramatically decreases transmissionratesdespitetheavailablevastopticalbandwidth.Modelingandequal- ization ofLEDresponseisakeyissuetoutilizetheopticalbandwidth.Researcherstendtouse high ordermodulationschemes.However,increasingsymbolrates,introducesinter-symbol- interference (ISI)andresultsinclosedeye-diagrams.Thatiswhytransmittinghighdata-rate signals throughband-limitedchannelsareusuallyaccompaniedbyequalizationandfiltering stages. NyquistbasedpulseshapingtechniqueachievesthebestsolutionforminimumISI at theminimumtransmissionbandwidthpossibleinanoise-freeenvironment.Nyquistpulse shaping suppressesoutofbandemissionwithinthelimitedbandwidthoftheLED. Another limitationinVLCistheLEDcurrent-powercurvewhichexhibitscertainnonlinear- ity.Whenincreasingthedrivingcurrent,heatincreases,andnon-radiativere-combinations become dominant.Consequently,LEDnonlinearitycanbeconsideredasthemajorsourceof nonlinearity intheVLClink.Indeed,itseverelydistortsthesignalsinsystemswithhighmod- ulation order,e.g.,orthogonalfrequencydivisionmultiplexing(OFDM),carrierlessamplitude and phasemodulation(CAP),andpulseamplitudemodulation(PAM),andaccordingly,itlim- its thetransmissionrates.That’swhynonlinearityisanothermajorobstacleforhigh-capacity VLC systems,whichisbeingtackledbyseveralequalizationtechniques. In thisthesis,weproposeanoveltransmittersystemtocompensateforthetwomainlimitations in LEDbasedVLCsystems.DifferentpulseshapingNyquistfilteringareappliedtoreduceISI within asmallbandwidth.Inaddition,weproposeapre-equalizertoalleviatenonlinearity. Results showanoveralllineartransmissionandasignificantimprovementinsymbol-error rates (SER)andeyediagrams.Moreover,weareabletoreduceout-of-bandsidelobesthus requiring smallerbandwidthforsignaltransmissionwithoutlossofinformation.