Wireless Communications（西安電子科技大學）知道智慧樹章節(jié)答案

目錄第一章單元測試第二章單元測試第三章單元測試第四章單元測試第五章單元測試第六章單元測試第七章單元測試第八章單元測試第一章單元測試1【判斷題】(1分ThemobiletelephonenetworkinNewYorkcouldonlysupportsmallnumberofsubscribersmainlybecausethepowerofthebasestationistoolow.（）正確答案：BA.對B.錯2【判斷題】(1分ThefirstgenerationWLANdeviceshadtouselowpowerdensityschemebecausehighpowerdevicesareveryexpensive.（）正確答案：BA.對B.錯3【單選題】(2分)正確答案：A__isnotthereasonthatwhythe1stgenerationWLANisnotwidelyused.（）A.Lackofmobility.B.Shortcoverage.C.Lackofstandardization.D.Lowdatarate.4.【多選題】(3分)正確答案：AC__and__aretwomaindisadvantagesforhighaltitudeorbitssatellitecommunications.（）A.bigpropagationdelayB.smallcoverage.C.HighpathlossD.multipathinterference.5.【多選題】(3分)正確答案：ABDThefirstwirelesscommunicationnetworksinthePre-industrialagetransmittedinformationbyusingsomesimplesignals,suchlike__signals,__signal,signal___,orbeatingdrums.（）A.flaresB.fireC.laserD.smoke第二章單元測試1.【多選題】(3分)正確答案：ABWhatcancausepowervariationinthereceivedsignaloverthedistance?（）A.shadowingeffectsB.pathlossC.constantsignalsourcepowerD.free-spacepropagation2【單選題】(2分)正確答案：AWhichfrequencybandisusedfortelevisioncommunicationsandradionavigationsystems?（）A.3MHz-30MHzB.30MHz-300MHzC.300MHz-3GHzD.3kHz-30kHz3【判斷題】(1分PathlossandShadowingaregenerallyreferredaslargescalepropagationeffects.（）正確答案：AA.對B.錯4【判斷題】(1分Fresnelknifeedgediffractionmodeliscommonlyuseddiffractionmodel.（）正確答案：BA.錯B.對5【判斷題】(1分Shadowingiscausedbytheamplificationofthepowerradiatedbythetransmitterandthereflectiveeffectsofthepropagationchannel.（）正確答案：BA.對B.錯第三章單元測試1.【多選題】(3分)正確答案：ABCDTherearemanyphysicalfactorsintheradiopropagationenvironmentinfluencesmall-scalefading，suchas____.（）A.MultipathpropagationB.ThesignalbandwidthC.RelativemotionofthereceiverandtransmitterD.Relativemotionofthereceiverandsurroundingobjects2【單選題】(2分)正確答案：BForamodulatedsignal,ifthesignalbandwidthislessthanthechannelcoherencebandwidth,thesignalthatpassesthechannelwillexperience____.（）A.multipathfadingB.flatfadingC.RayleighfadingD.frequency-selectivefading3【判斷題】(1分TherelativemotionbetweenthereceiverandthetransmitterresultinrandomfrequencymodulationduetodifferentDopplershiftsoneachofthemultipathcomponents.（）正確答案：AA.對B.錯4【判斷題】(1分Whenthechannelrmsdelayspreadismuchmorethanthesymbolduration,thechannelisregardedasfrequency-selectivefadingchannelorwidebandchannel.（）正確答案：AA.對B.錯5【判斷題】(1分Inthelinkbudgetofmobilecommunications,fademarginisnotnecessarilyconsidered.（）正確答案：BA.對B.錯第四章單元測試1.【多選題】(3分)正確答案：ABDThefollowingarecomponentsofthetransmitterofacommunicationsystem.（）A.sourcecoderB.modulatorC.equalizerD.channelcoder2【判斷題】(1分Atreceiver,thelocaloscillator(LO)whichisgeneratedandtrackedbyacarrierfrequencyrecoverycomponentprovidesanunmodulatedsinusoidalsignal,toconverttheradiofrequencysignalintoabasebandsignal.（）正確答案：AA.對B.錯3.【多選題】(3分)正確答案：CDIfthereareMsymbolandeachsymbolhasKbits,i.e.M=2K.AssumethesymboldurationisT,thedatarateofthesystemis__.（）A.K*TB.M/TC.K/TbpsD.log2M/Tbps4【判斷題】(1分Indemodulation,minimizingthesymbolerrorprobabilitycorrespondstofindtheconstellationsithatmaximizesp(si|r),whereristhereceivedvector.（）正確答案：BA.錯B.對5.【多選題】(3分)正確答案：ABC___areperformancecriteriaareusedtodescribetheperformanceofdigitalmodulationsoverfadingchannelsdependsontherateofchangeoffading.（）A.TheaverageerrorprobabilityB.TheoutageandaverageerrorprobabilitycombinedC.Theoutageprobability,PoutD.BER第五章單元測試1.【多選題】(3分)正確答案：ABC___，___and___aretechniqueswhichcanbeusedtoimprovethelinkqualityofwirelesschannels.（）A.EqualizationB.ChannelcodingC.DiversityD.Sourcecoding2【單選題】(2分)正確答案：C___selectsthebranchwiththehighestSNRastheresultdiversityoutputanddiscardsotherbranches.（）A.ThresholdcombiningB.MaximalRatiocombiningC.SelectioncombiningD.Equalgaincombing3【單選題】(2分)正確答案：AWhichofthefollowingstatementsistrueaboutchannelcoding?（）A.Itcanbothdetectandcorrecterrors.B.Itcanonlydetecterrors,notcorrectthem.C.Ithasnoeffectonerrorcorrectioninwirelessfadingchannels.D.Itcanonlycorrecterrors,notdetectthem.4【判斷題】(1分Inthedecodingprocessofblockcoding,ifthesyndromevectorhasall-zeroentries,thereceivedcodewordisalwaysvalid.（）正確答案：AA.對B.錯5【單選題】(2分)正確答案：BWhatarethetwomaincategoriesoftimedomainequalization?（）A.SimpleandcomplexB.LinearandnonlinearC.Decision-feedbackandmaximumlikelihoodsequenceestimationD.Frequencydomainandtimedomain第六章單元測試1.【多選題】(3分)正確答案：ABCDInspreadspectrumcommunications,thesignalisspreadbyaPNcodeatthetransmitteranditiscorrelatedbythesamePNcodeatthereceiver,whichhasmanyadvantages,including:____.（）A.LowprobabilityofinterceptionB.Highcapabilityofanti-fadingC.StrongresistancetomultipathinterferenceD.Stronganti-interferencecapability2【單選題】(2分)正確答案：DToguaranteethespreadingcodegeneratedinthereceivercansynchronizewiththespreadingcodeinthereceivedsignal,____isneeded.（）A.frequencysynchronizationB.powersynchronizationC.phasesynchronizationD.timesynchronization3【判斷題】(1分Spreadspectrumcanbetakentoimproveperformanceofwirelesscommunications.（）正確答案：BA.錯B.對4【判斷題】(1分Spreadspectrumcommunicationisasingle-accesscommunicationmethodthatdistinguishescommunicationaddressesbyfrequencydifferences.（）正確答案：BA.對B.錯5【判斷題】(1分Awaytoimprovetheworkingspeedofpseudo-randomsequenceistoadoptMSRGstructure.（）正確答案：BA.錯B.對第七章單元測試1.【多選題】(3分)正確答案：ACDWhatisthepurposeofmulticarriermodulation?（）A.ToimprovetheperformancethroughdiversityB.ToovercomeDopplershiftproblemC.TodivideahighspeeddatastreamintomanylowspeedsubstreamsD.Tochangefrequencyselectivefadingintoflatfading2【單選題】(2分)正確答案：CWhereisthecyclicprefixaddedinanOFDMsystem?（）A.DuringtheDFTdemodulationprocessB.AftertheOFDMsignalisreceivedatthereceiverC.BeforetheOFDMsignalissenttothechannelfortransmissionD.BeforetheIDFTmodulationprocess3【單選題】(2分)正確答案：DWhatisthematrixHusedtorepresentinaMIMOchannelmodel?（）A.ThechannelgainfromeachtransmitantennatoreceiveantennapairB.TheestimatedaccuracyofthechannelatthereceiverC.ThenumberoftransmittingandreceivingantennasinaMIMOsystemD.Thecomplexgainfactorfromeachtransmitantennatoreceiveantennapair4【單選題】(2分)正確答案：AWhenboththereceiverandtransmitterknowtheCSI,howcanthecorrespondingpowerallocationpolicybeobtainedforthemaximumchannelcapacity?（）A.Itisobtainedbyusingwaterfillingalgorithm.B.ItisobtainedbyequallyallocatingthepowerPi.C.Itisobtainedbyaveragingthepowerallocationonthetransmittingantenna.D.ItisobtainedbyusingSVD.5【單選題】(2分)正確答案：CWhatisthemainideaofspatialdiversityinMIMO?（）A.Todecreasethereliabilityofcommunicationbyusingspatialredundancytotransmitdatacontainingthesameinformationonaparallelchannelinspace.B.Todecreasethecomplexityofcommunicationbyusingspatialredundancytotransmitdatacontainingthesameinformationonaparallelchannelinspace.C.Toincreasethereliabilityofcommunicationbyusingspatialredundancytotransmitdatacontainingthesameinformationonaparallelchannelins