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1、无线信号的传播环境对PHS网络RF优化的影响（）Atpresent,PHSnetworkhasaconsiderableshareinthemobilecommunicationnetwork.Itstotalnumberofusershasexceeded10million,morethanthetotalnumberofCDMAnetworkusers,andamonthlynetincreaseof500thousandusersrapiddevelopment.WiththedevelopmentofPHSnetwork,"PHS"us
2、ersarebeginningtoexpandfromlow-endtomediumandhigh-end,andPHSnetworksfromsmallandmediumcitiestolargeandmediumcities.Comparedwithsmallandmedium-sizedcities,theurbanenvironmentinlargeandmedium-sizedcitieshasnotablecharacteristics.Forexample,manyhigh-risebuildings,andmanyhigh-en
3、dusers;manyvehicles,carphoneusegenerallyinsomesections,fasterspeed;userintensiveareas,thebasestationdensity;electronicjammingsourcespectrumofpotentialincreasesandsoon.PHSnetworkcoverageischaracterizedbysmallCELLradius,lowbasestationmobilephonepower,lowantennaheight,asmallnum
4、berofsinglebasestationchannelsandsoon.AlloftheseputforwardhigherrequirementsforournewRFplanningandoptimization.Inthispaper,wewillintroducesomebasiccharacteristicsofwirelesssignalpropagationinmobilecommunications,andgivesomesimpleexplanationstosomephenomenaincurrentnetworks,a
5、ndprovidethepossiblesolutions.1.multipatheffectIntheactualenvironment,thepropagationofradiowavesisverycomplexandmaybeaffectedbyvariousfactors.Oneofthemostimportantfactorsisthemultipatheffect.Itreferstothewavealongthepropagationpathofpropagationduetoreflection,diffractionandt
6、ransmission,whichreachthepartofthesignalreceivingantennaandthephaseandamplitudechanges,whenallsignalsincludingdirectwave,reachthereceivingpositionafterthesuperpositionofsignalenergyisreducedorincreased,resultingincommunicationsignalinstability.Producemultipathfading.Intheory
7、study,multipathfadingcanbedescribedbyRayleighdistribution,soitiscalledRayleighfadingandmultipathfading;duetochangesinspaceortimeisfast,itissometimescalledfastfading(smallscalefading).Inmobilecommunications,multipathfadingcannotbecompletelyeliminated,wecanonlythinkofwaystored
8、uceitsimpact,themainmethodissignaldiversity.Accordingtotheprincipleofdivers
