无线通信基础(双语)_教学课件_5.ppt

无线通信基础(双语)_教学课件_5.ppt

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PropagationOverSmoothPlane,Two-pathmodelCriticaldistance,ReviewofLastClass,DiffractionandFresnelZones,ReviewofLastClass,Log-DistancePathLosswithShadowing,ReviewofLastClass,Log-DistancePathLossModelLog-NormalShadowingLog-TermFading,Asimplemodelsimilartofree-spacemodel,Averagereceivedsignalpowerdecreaseslogarith-micallywithdistancedandpathlossexponentk,Pathloss:

attenuationofthesignal,4、Log-DistancePathLosswithShadowing,Log-DistancePathLossModel,Importantparameter:

path-lossexponentkPowerlossmorewithlargek,kdependsonenvironment,4、Log-DistancePathLosswithShadowing,Log-DistancePathLossModel,d0istheclose-inreferencedistance,typically:

1kmformacrocells100mforoutdoormicrocells1mforindoorpicocells,4、Log-DistancePathLosswithShadowing,Log-DistancePathLossModel,Ifmeasuredpowerlossis70dBatd0=10m,and110dBatd=100m.Whatispath-lossexponentk?

Whatenvironmentismostlylikely?

Example2.6,4、Log-DistancePathLosswithShadowing,MajoradvantageofthismodelSimple,generalapplicabilityMajordisadvantageNotaccurate,cannotdescriberandomeffect,4、Log-DistancePathLosswithShadowing,Log-DistancePathLossModel,Withrandom（arbitrary）shadowing,pathlossesaredifferentevenamongMSwithsameT-RdistanceDuetovariouscluttersonpath,shadowingeffectisrandomPathlossisalsorandom,andusuallynormal（indB）Wehavelog-normaldistributionofpathloss（aboutameanvalue）,4、Log-DistancePathLosswithShadowing,Log-NormalShadowing,Letbeazero-meanGaussiandistributedrandomvariable（indB）withstandarddeviation.Thepdfofisgivenby,Forexample,8dBisatypicalvalueforinanoutdoorcellularsystemand5dBisavalueforanindoorenvironment.,4、Log-DistancePathLosswithShadowing,Log-NormalShadowing,Asaresult,long-termfadingisacombinationoflog-distancepathlossandlog-normalshadowing.LetdenotetheoverallpathlosswithshadowingindB.Then,4、Log-DistancePathLosswithShadowing,Log-TermFading,Receivedsignalpower,Note:

bothPr（d）andLp（d）areGaussianrandomvariableswithcertainmeanandvariance2.,4、Log-DistancePathLosswithShadowing,Log-TermFading,Duetotherandomnatureofthelog-termfading,thepathlossalwaysdefinedaswhichislimitedtodBwithapre-definedprobability.,4、Log-DistancePathLosswithShadowing,Log-TermFading,4、Log-DistancePathLosswithShadowing,Example2.7Leftmeasurementtable,assumelog-normalmodel,andd0=100mFindpathlossexponentk.Findvariance2.Predictreceivedpoweratd=2km.,4、Log-DistancePathLosswithShadowing,SolutiontoExample2.7,TakeexpectationE（）:

4、Log-DistancePathLosswithShadowing,SolutiontoExample2.7,Withk=4.5,wehavesamplesof,Samplevaricance:

Averagereceivedpower:

-57dBm,4、Log-DistancePathLosswithShadowing,2.4Large-scalepathlossandshadowing,ApplicationsofpathlossmodelsUsedforlink-budgetdesignPredictlargescalecoverageformobilesystems,Log-TermFading,Chapter2-Lecture4,Large-scalepathlossandshadowing（3）,2.4.2PropagationOverSmoothPlane,2.4.4Log-DistancePathLosswithShadowing,2.4.1FreeSpacePropagation,2.4.5Indoor/OutdoorPathLossModel,2.4.3DiffractionandFresnelZones,2.4Large-scalepathlossandshadowing,2.4.6RadioCellCoverage,Radiocellcoverageistheserviceareasupportedbyeachbasestation.ThecoveragedependsonServicequalityrequirementsThepropagationenvironment,theservicequalitycriterionisspecifiedintermsofthepropagationpathloss,thelog-termfadingmodel,6、RadioCellCoverage,Considerthelog-termfadingmodel.DeterminethecellcoverageforthefollowingtwosituationsWithoutshadowingWithshadowing,6、RadioCellCoverage,Example2.8,a）Withoutshadowing,itisrequiredthat,atthecellborder,thepathlosscannotbedBlargerthanthatatthereferencedistanced0,ThepathlossindBatadistanced（dd0）fromthebasestationis,ThecellcoverageisacirclecenteredatthebasestationwithradiusRspecifiedby,6、RadioCellCoverage,Example2.8,ShowingtheaboveequationfortheradiusR,weobtain,a）Withoutshadowing,itisrequiredthat,atthecellborder,thepathlosscannotbedBlargerthanthatatthereferencedistanced0,6、RadioCellCoverage,Example2.8,b）Withshadowing,thecellcoverageisdefinedastheserviceareaofthebasestationoverwhichthepathlossislimitedtodBwithapre-definedprobability.Andassumethereferencedistanced0isverysmallcomparedwiththecellradius.,6、RadioCellCoverage,Example2.8,Theproblemofestimatingthecellcoveragecanbeapproachedintwosteps:

Step1:

Determinetheprobabilitya1thatthepathlossatlocationr（d0）isbelowthethreshold,wheretheprobabilityisaveragedoverthecircumference;Step2:

Calculatetheprobabilitya2ofthecirculararea（definedbyR）overwhichthepathlossisbelowthethresholdbasedona1,wheretheprobabilityisaveragedoverthecirculararea（cellarea）.,6、RadioCellCoverage,Example2.8,Therelativepathlossatdwithrespecttothelossatd0isgivenby,Withshadowing,thepathlossindBatadistanced（d0）fromthebasestationis,b）Withshadowing,assumethereferencedistanced0isverysmallcomparedwiththecellradius.,6、RadioCellCoverage,Example2.8,Atthedistanced=r（d0）,theprobabilitythattherelativepathlossislimitedtodBis,b）Withshadowing,assumethereferencedistanced0isverysmallcomparedwiththecellradius.,6、RadioCellCoverage,Example2.8,b）Withshadowing,assumethereferencedistanced0isverysmallcomparedwiththecellradius.,Whereforand,Next,wewanttofindtheprobabilitya2oftheeventoveracircularareaAcenteredatthebasestationwithradiusR.,6、RadioCellCoverage,Example2.8,Thus,wehave,b）Withshadowing,assumethereferencedistanced0isverysmallcomparedwiththecellradius.,6、RadioCellCoverage,Example2.8,where,Ifd0R,wehave,b）Withshadowing,assumethereferencedistanced0isverysmallcomparedwiththecellradius.,6、RadioCellCoverage,Predictthesignalstrengthbyconsideringalsotheterrainprofile.Thisismoreaccuratethanthestatisticalapproachoflog-distancepathlossmodel,buthasalsomorelimitedapplicationsMostofsuchmodelsareobtainedfromsystematicinterpretationofmeasurementdataTheirapplicationislimitedtosimilarenvironments,5、Indoor/OutdoorPathLossModel,5、Indoor/OutdoorPathLossModel,OkumuraModelOkumura-HataPathLossModelCOST231ModelLeesPathLossModel,OneofthemostcommonmodelsforsignalpredictioninlargeurbanmacrocellsOkumurausedextensivemeasurementsofbasestation-to-mobilesignalattenuationthroughoutTokyotodevelopasetofcurvesgivingmedianattenuationrelativetofreespaceofsignalpropagationinirregularterrain,5、Indoor/OutdoorPathLossModel,OkumuraModel,TheOkumuramodelisrestrictedtothefollowingrangeofparameters:

Thecarrierfrequency,150,1500MHzAntennaheightsofbasestationandmobilestation,hb30,100mThedistancebetweenthebasestationandmobilestation,1,100Km,5、Indoor/OutdoorPathLossModel,OkumuraModel,ThepathlossindBisgivenby,5、Indoor/OutdoorPathLossModel,OkumuraModel,ThevalueofandobtainedfromOkumurasempiricalplots.Okumuraderivedempiricalformulasfor,5、Indoor/OutdoorPathLossModel,OkumuraModel,5、Indoor/OutdoorPathLossModel,OkumuraModel,TheOkumuramodelhasa1014dBempiricalstandarddeviationbetweenthepathlosspredictedbythemodelandthepathlossassociatedwiththemeasurementsusedtodevelopthemodel.,5、Indoor/OutdoorPathLossModel,OkumuraModel,EmpiricalformulationtomatchOkumuramodelSuitableforlargecell,5、Indoor/OutdoorPathLossModel,Okumura-HataPathLossModel,ThepathlossisrepresentedasafunctionofThecarrierfrequency,150,1500MHzAntennaheightsofbasestationandmobilestation,hb30,200m,hm1,10mThedistancebetweenthebasestationandmobilestation,1,20Km,5、Indoor/OutdoorPathLossModel,Okumura-HataPathLossModel,ThepathlossindBisgivenby,where,5、Indoor/OutdoorPathLossModel,Okumura-HataPathLossModel,a（hm）isthecorrectionfactorformobileantennaheight,andisgivenby,Forasmallandmediumcity,Foralargecity,5、Indoor/OutdoorPathLossModel,Okumura-HataPathLossModel,fc=900MHzhb=50mhm=3m,5、Indoor/OutdoorPathLossModel,Okumura-HataPathLossModel,TheHatamodelwasextendedbytheEuropeancooperativeforscientificandtechnicalresearch（EURO-COST）to2GHz,Wherea（hr）isthesamecorrectionfactorasbeforeandCMis0dBformediumsizedcitiesandsuburbsand3dBformetropolitanareas.,5、Indoor/OutdoorPathLossModel,COST231Model,TheCOST231modelisrestrictedtothefollowingrangeofparameters:

Thecarrierfrequency,1.5,2GHzAntennaheightsofbasestationandmobilestation,hb30,200m,hm1,10mThedistancebetweenthebasestationandmobilestation,1,20Km,5、Indoor/OutdoorPathLossModel,COST231Model,Leesmodelcanbeusedtopredictarea-to-areapathloss.Themodelconsistsoftwoparts:

PathlosspredictionforaspecifiedsetofconditionsAdjustmentfactorsforasetofconditionsdifferentfromthespecifiedoneThemodelrequirestwoparameters:

Thepowerata1.6km（1mile）ofinterceptionP0indBmThepath-lossexponentk.,5、Indoor/OutdoorPathLossModel,LeesPathLossModel,Thespecifiedsetofconditionsisasfollows:

Carryfrequencyfc=900MHzBasestationantennaheight=30.48m（100ft）Basestationpowerattheantenna=10WBasestationantennagain=6dBabovedipolegainMobilestationantennaheight=3m（10ft）Mobilestationantennagain=0dBabovedipolegain,5、Indoor/OutdoorPathLossModel,LeesPathLossModel,5、Indoor/OutdoorPathLossModel,LeesPathLossModel,ThereceivedsignalpowerindBmisrepresentedby:

Whered0=1.6km,d（d0）isthedistancebetweenthemobilestationandthebasestationinkm,andnisaconstantbetween2and3dependentonthe