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45;rangeindoorwirelessmunicationsystemsprovidingveryhighbitratesservices,lowpowerconsumption,high-security,lowplexityandsoon[1].TheUWBbandwidthisverylargeduetoitsusingsub-nanosecondpulses,whichisoneofthemostimportantadvantagesofUWB.Butunfortunately,theverylargebandwidthrequiredbytheUWBsignalscannotbeallocatedexclusively,namely,UWBbandoverlapswiththebandsallocatedtomanyothernarrow-bandsystemssuchasthe3rdgenerationmobilemunicationsystemswhicharemainlybasedonWCDMA,CDMA2000andTD-SCDMA.本文出处 http://www.sxsky.net/xie/070320369.html
Inthispaper,amathematicalmodelisestablishedtoevaluatetheUWBinterferencetoWCDMA,CDMA2000andTD-SCDMA.ComparisonandanalysisresultsonthemaximumacceptableUWB-devicedensityofdifferent3GsystemsaregivenwithrespecttoFCC,ETSIandJapanregulationsrespectively.
2.UWBInterferenceModel
SincethebasestationsaregenerallyinelevatedlocationsandtheUWBpropagationdistanceisveryshort,theUWBinterferenceeffectswillbefeltmainlyatthemobileterminal.Hence,weonlyconsidertheeffectsonthedownlink.WewillconsiderasituationinwhichUWBdevicesareusedindoorandnotactiveatalltimes.Theinterferenceeffectsaresimulatedwithrespecttoagivenactivityfactor.
2.1integralmodelofhollowSphericaldistribution
Fig.1showstheUWBinterferencemodelconsideredinthispaper.Inthisthreedimensionalmodel,ourvictimreceiver,the3Gmobileterminal,islocatedinthecenterofahollowspherewithradiusrminandrmax,andourjammers,theUWBdevices,areuniformlydistributedperunitvolumeoverthehollowsphere.TheprobabilitydensityfunctionoftheUWBtransmittersasafunctionoftheradiusrisexpressedby:
Themeaninterferenceleveltothe3GterminalisgivenbythemeanreceivedpowerfromalltheUWBtransmitters,namely:
Where,NisthenumberofUWBtransmittersinthehollowsphereandisthedensityofUWBdevicesperunitvolume,P(r)representsthereceivedsignalpowerfromasingleUWBtransmitterasafunctionofthedistancebetweenthem,andκistheactivityfactor.WecanwriteP(r)as:
Where,PtistheemissionpowerofasingleUWBtransmitterandassumedtobeequalforallUWBterminals,λisthewavelengthofthesignalandassumedtocorrespondtothefrequencyoftheaffected3Gdevices,Bristhebandwidthofthevictimreceiver,andGt,GraretheantennagainoftheUWBtransmitterandthevictimreceiverrespectively.Hence,(2)canberewrittenas:
2.2performancedegradationmodelof3Greceiver
Theperformancedegradationparameterofthevictimreceiverisdefinedastheradiooftheinterferencenoisethresholdtothenoisethreshold,namely:
Where,NoisthenoisethresholdofthevictimreceiverandIUWBistheUWBinterferencetothevictimreceiverwithoutrespecttotheotherkindsofinterferencetothevictimreceiversuchasco-channelinterferencebetweentwo3Gdevices.NUWBrepresentsthelinkbudgetdegradationofthevictimreceiverfortheexistenceoftheUWBinterference.Inthiscase,themaximumacceptableUWBinterferencethresholdcanbeanalyzedbycalculatingthedegradationlevelofthelinkbudgetmargin.ThemaximumacceptableUWBinterferencepowerisexpressedby:
2.3UWBinterferenceto3Gdevices
InordertofindouttheUWBinterferenceeffecton3Gdevices,weestablishtherelationshipbetweentheUWBtransmitterdensityρandtheperformancedegradationparameterNUWBofthevictimreceiver.Itcanbegottenfrom(4)and(6)that:
Namely,ρasafunctionofNUWBcanbeexpressedby:
Inthiscase,PtisobtainedaccordingtodifferentUWBemissionmasks(FCC,ETSI,JAPAN),andtheactivityfactorκissetat5%accordingtotheFCCstipulation(i.e.5%oftheUWBtransmittersareactiveonaverageatacertaintime).WeassumethatGtandGrareequalto0dB,otherwiseitcanbeconsideredinthelinkbudgetmargin.ConsideringtheUWBradiationradiusisveryshortforthelowemissionpower,rmaxissetat30meters,andrmin等于0.5meterisrationalinindoorenvironment.Obviously,(8)givesusthemaximumacceptableUWBdevicedensityunderdifferentlinkbudgemarginfor3Gterminals.
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3.Simulations
Thesimulationsareinindoorenvironmentwithoutrespecttothesignalattenuationbywalls.TheparametersusedinthesimulationsaregivenbyTableIandTableII.Fig.2,Fig.3andFig.4showthesimulationresultsunderdifferentUWBemissionpowerlimitregulationsofFCC,ETSIandJapanrespectively.TheUWBdevicedensityincreaseswhenNUWBbeeslarger.Allthethreefiguresshowthattheanti-UWB-interferencecapabilityofTD-SCDMAisstrongest,andtheoneofWCDMAisweakest.TheUWBinterferenceimmunityofCDMA2000liesbetweenthem.Fig.2showsthatinordertogetUWBdevicedensityρabove0.1/m3whichisacceptable,thelinkbudgetmarginNUWBshouldbegreaterthan17dB,20dBand23dBforTD-SCDMA,CDMA2000,andWCDMArespectivelyunderFCCUWBemissionpowerlimitregulation.ButunderETSIproposedregulation,TD-SCDMAonlyneedslinkbudgetmarginabove3dBforUWBdevicedensityabove0.1/m3,and
CDMA2000andWCDMAneed10dBand12dBrespectively,asfig.3shows.Itcanalsobe
操作系统方面有关论文范文,与本科生毕业设计文规范,本科生文文献综述北京DOC相关论文答辩开场白参考文献资料：