英文版02 无线传输基础课件.ppt

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1、WirelessTransmissionBasicsFrequenciesSignalsAntennaSignalpropagationMultiplexingModulationSpreadspectrumCoding1ReferenceBooks“WirelessCommunications&Networks”,W.Stallings,2005,PrenticeHall“DataandComputerCommunications”,W.Stallings,2007,PrenticeHall“WirelessCommunications–Principlesandpractice”,

2、T.Rappaport,2002,PrenticeHall2FrequenciesforcommunicationVLF=VeryLowFrequencyUHF=UltraHighFrequencyLF=LowFrequencySHF=SuperHighFrequencyMF=MediumFrequencyEHF=ExtraHighFrequencyHF=HighFrequencyUV=UltravioletLightVHF=VeryHighFrequencyFrequencyandwavelength:=c/fwavelength,speedoflightc3x108m/s,freq

3、uencyf1Mm300Hz10km30kHz100m3MHz1m300MHz10mm30GHz100m3THz1m300THzvisiblelightVLFLFMFHFVHFUHFSHFEHFinfraredUVopticaltransmissioncoaxcabletwistedpair3Transmissionmedium,frequency,&characteristicsIncaseofwiredcommunication,transmissionmediummostlydeterminesthetrans.characteristicsTwistpairCoaxialcabl

4、eOpticalfiberIncaseofwirelesscommunication,frequencyspectrum,bandwidth,andantennadeterminesthetrans.CharacteristicsMediumisair(orvacuum)anywayWewanttounderstandrelationsbetweenvariousfactorsSignalpower,thermalnoise,interference,attenuation,…Frequency,bandwidth,datarate4Frequenciesformobilecommunica

5、tionVHF-/UHF-rangesformobileradiosimple,smallantennaforcarsdeterministicpropagationcharacteristics,reliableconnectionsSHFandhigherfordirectedradiolinks,satellitecommunicationsmallantenna,beamforminglargebandwidthavailableWirelessLANsusefrequenciesinUHFtoSHFrangelimitationsduetoabsorptionbywaterando

6、xygenmoleculesweatherdependentfading,signallosscausedbyheavyrainfalletc.5FrequenciesandregulationsITU-Rholdsauctionsfornewfrequencies,managesfrequencybandsworldwide(WRC,WorldRadioConferences)6SignalsIphysicalrepresentationofdataclassificationcontinuoustime/discretetimecontinuousvalues/discretevalue

7、sanalogsignal=continuoustimeandcontinuousvaluesdigitalsignal=discretetimeanddiscretevaluessignalparametersofperiodicsignals:periodT,frequencyf=1/T,amplitudeA,phaseshiftsinewaveasspecialperiodicsignalforac