通信工程 毕业设计外文文献翻译:超宽带系统的数据通信文档格式.docx
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通信工程 毕业设计外文文献翻译:超宽带系统的数据通信文档格式.docx
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10240FlandersCt.SanDiegoCA92121
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{gopal.racherla,jason.ellis,susan.lin,david.furuno}@Website:
luwb
ABSTRACT
Ultra-Widebandt(UWB)isaradiotransmissionschemethatusesextremelylowpowerpulsesofradioenergyspreadacrossawidespectrumoffrequencies.UWBhasseveraladvantagesoverconventionalcontinuouswaveradiocommunicationsincludingpotentialsupportforhighdatarates,robustnesstomultipathinterferenceandfading.WepresentanoverviewofUWBtechnologyanditsuseindatacommunicationsandnetworking.WelookatdesignconsiderationsforUWBbasednetworksatvariouslayersoftheprotocolstack.
1.INTRODUCTION
Ultra-Wideband[1-6]一alsoknownasbasebandorimpulseradio一isacarrier-freeradiotransmissionthatusesnarrow,extremelylowpowerpulsesofradioenergyspreadacrossawidespectrumoffrequencies.UWBhasrecentlygainedagreatdealofinterestduetotherecentFederalCommunicationsCommission(FCC)ReportandOrderwhichallocatestheUWBband一7.5GHzofunlicensedspectrumforindoorandoutdoorcommunicationapplications.UWBcommunicationsarerequiredtohavea-10dBfractionalbandwidthofmorethan20%ora-10dBbandwidthofmorethan
500MHz[7].ItisimportanttonotethattheFCChasnotdefinedaspecificmodulationschemetobeused.UWBsystemsofferthepromiseofhighdatarate,lowsusceptibility
tomultipathfading,hightransmissionsecuritylowprimepowerrequirements,lowcost,andsimpledesign[1,2,5,6].UWBhasbeenusedinmilitaryapplicationsforthepastseveralyearsforground-penetratingprecisionradarapplicationsandsecurecommunications[3,8].Forthepastfewyears,UWBhasbeendevelopedforcommercialapplications[1,2,5,6].WiththerecentFCC[7]reportandorderforthe
useofUWBtechnology,therehasbeenanaddedimpetustothisendeavor.OthernotableUWBapplicationsincludecollisionavoidanceradar,tagging/identification;
geolocation[9]anddatacommunicationsinpersonalareanetworks(PAN)andlocalareanetwork(LAN)environments.
UWBpresentsagreatopportunityfordatacommunicationsfortoday'
smedia-richconsumerelectronicsandhomeentertainmentsystemsthatrunonbatterypoweredhandhelddevices.Itcanformthebasisofalowcost,lowpowerandveryhighdataratesolutionasawireless"
cablereplacement"
technologyforcomputer-to-peripherals,peripherals-to-peripheralsanddigitalhomenetworkingapplications.AveryusefulattributeofUWBtechnologyisitsabilitytoperformprecisiongeo-locationwhichcanaidinad-hocormeshnetworkingwheretheoperationsofthemobilehostsbenefitbyknowingthelocationoftheotherhosts.UWBtechnologypromisestofillthevoidleftbyestablishedstandardslikeBluetoothand802.11a/b/g.
ThereareseveralfuturechallengestothewideadoptionofUWBforwirelessdatacommunicationsincludingtheinfancyofthetechnologyinthecommercialarena,lackofreliable
channelmodels,theearlystagesofstandardizationeffortandlackoflow-costsystemonchip(SoC)implementations.Inthispaper,welookatUWBtechnologyfordatacommunicationsandinsideaUWBphysical(PHY)layercharacteristics.Wealsobrieflyintroduceotherrelatedwirelessstandardssuchas802.11[10],802.15.3[11-13]Bluetooth[14],HomeRF[15]andHIPERLAN[16]andpresentabriefsynopsisoftheregulatoryeffortworldwidewithspecialemphasisontheFCC.WealsopresentthedesignconsiderationsforUWBbaseddatanetworking.
2.ULTRA-WIDEBANDTECHNOLOGY
ThebasicwaveformthatemployedinaUWBsystemisanapproximationtoanimpulse,suchasthatshowninFig.1.Theshortdurationofthepulseisassociatedwithlargeinherentbandwidth;
hence,thenomenclature"
Ultra-Wideband"
.TypicalattributesofUWBwaveformsaresummarizedinTable1.
Fig.1.UWBwaveformexample.
ThehighspectralcontentoftheUWBwaveformgivesrisetooneoftheprimaryadvantagesUWBoperationforcommunicationswhereaUWBsystemisrobustagainstmultipathfading[17]andnarrowbandinterference[18].Inmultipathfading,wherethetransmittedradiofrequency(rt)signalcanreflectoffobjectsinitstransmissionpathandcancausedestructiveinterferencesatthereceiver,alossofreceptioncanoccur.This
Table1:
CharacteristicsofTypicalUWBSystemsFractionalBandwidth>
20%
PulseWidth0.1-2as
PulseRepetitionFrequency1kHz-2GHzAverageTransmittedPower<
1mW
effectisparticularlyproblematicindoorswheretherearemanyreflectingsurfaces.Inthefrequencydomain,multipathisshownasfrequencyselectivefading.BecauseUWBcommunicationssystemsspreadsthetransmitteddataoverabroadfrequencybandifd
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