无线通信基础(双语)_教学课件_ .ppt

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1、ReviewofLastClass2、Timedispersion3、ImpairmentsoftheWirelessChannel1、FourBasicPropagationMechanismFadingLarge-scalepathlossandshadowingSmall-scalefadingReviewofLastClassRadioPropagationModel“...characterizationofradiowavepropagationasafunctionoffrequency,distance

2、andotherconditions.”ReviewofLastClassGeneralray-tracingmethod(simulation)Multipleray-tracingwithpropagationeffects(reflection,diffraction,LOSpath,scattering,etc)Mightconsiderbuildingmaterial(steel,concrete,brick,etc)EmpiricalmethodOn-sitemeasurementCurve-fitting

3、StatisticalmethodReviewofLastClassChapter2----Lecture2Large-scalepathlossandshadowing(1)IllustrationDistanceinwavelengthSignalPowerT-RdistanceTXRXRXLarge-scalefree-spacelossShadowinglossSmall-scalefading2.4Large-scalepathlossandshadowingThepathlossisdependentont

4、hedistancebetweenthetransmitterandreceiverItalsodependsonthepropagationenvironmentTerraincharacteristicsWavelengthTransmittingandreceivingantennaheightsApathmodelisimportantfordeterminationofthebasestation(cell)coverageareaLarge-ScaleFading2.4Large-scalepathloss

5、andshadowing2.4.2PropagationOverSmoothPlane2.4.4Log-DistancePathLosswithShadowing2.4.1FreeSpacePropagation2.4.5Indoor/OutdoorPathLossModel2.4.3DiffractionandFresnelZones2.4.6RadioCellCoverageTheFriisEquationFree-SpacePathLoss1、FreeSpacepropagation2.4Large-scalep

6、athlossandshadowingNointerference,noobstructionsThereisnolossofenergyinfreespace,butthereisattenuationduetothespreadingofthewaves1、FreeSpacepropagationTheFriisEquationWhere:Pt=totalpowerradiatedbyanisotropicsourceGt=transmittingantennagainGr=receivingantennagain

7、d=distancebetweentransmittingandreceivingantennas=wavelengthofthecarriersignal=c/fcfc=carrierfrequency1、FreeSpacepropagationTheFriisEquationWhattroublessomepeoplewhentheyseethisquestionisthatthepathlossalsoincreasesasthesquareofthefrequency.Whileitistruethatabs

8、orptionofRFbyvariousmaterials(buildings,trees,watervapor,etc.)tendstoincreasewithfrequency,rememberwearetalkingabout“freespace”here.1、FreeSpacepropagationTheFriisEqua