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

目錄第一章單元測(cè)試第二章單元測(cè)試第三章單元測(cè)試第四章單元測(cè)試第五章單元測(cè)試第六章單元測(cè)試第七章單元測(cè)試第八章單元測(cè)試第一章單元測(cè)試1【判斷題】(1分ThemobiletelephonenetworkinNewYorkcouldonlysupportsmallnumberofsubscribersmainlybecausethepowerofthebasestationistoolow.（）正確答案：BA.對(duì)B.錯(cuò)2【判斷題】(1分ThefirstgenerationWLANdeviceshadtouselowpowerdensityschemebecausehighpowerdevicesareveryexpensive.（）正確答案：BA.對(duì)B.錯(cuò)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(cè)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(duì)B.錯(cuò)4【判斷題】(1分Fresnelknifeedgediffractionmodeliscommonlyuseddiffractionmodel.（）正確答案：BA.錯(cuò)B.對(duì)5【判斷題】(1分Shadowingiscausedbytheamplificationofthepowerradiatedbythetransmitterandthereflectiveeffectsofthepropagationchannel.（）正確答案：BA.對(duì)B.錯(cuò)第三章單元測(cè)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(duì)B.錯(cuò)4【判斷題】(1分Whenthechannelrmsdelayspreadismuchmorethanthesymbolduration,thechannelisregardedasfrequency-selectivefadingchannelorwidebandchannel.（）正確答案：AA.對(duì)B.錯(cuò)5【判斷題】(1分Inthelinkbudgetofmobilecommunications,fademarginisnotnecessarilyconsidered.（）正確答案：BA.對(duì)B.錯(cuò)第四章單元測(cè)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(duì)B.錯(cuò)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(cuò)B.對(duì)5.【多選題】(3分)正確答案：ABC___areperformancecriteriaareusedtodescribetheperformanceofdigitalmodulationsoverfadingchannelsdependsontherateofchangeoffading.（）A.TheaverageerrorprobabilityB.TheoutageandaverageerrorprobabilitycombinedC.Theoutageprobability,PoutD.BER第五章單元測(cè)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(duì)B.錯(cuò)5【單選題】(2分)正確答案：BWhatarethetwomaincategoriesoftimedomainequalization?（）A.SimpleandcomplexB.LinearandnonlinearC.Decision-feedbackandmaximumlikelihoodsequenceestimationD.Frequencydomainandtimedomain第六章單元測(cè)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(cuò)B.對(duì)4【判斷題】(1分Spreadspectrumcommunicationisasingle-accesscommunicationmethodthatdistinguishescommunicationaddressesbyfrequencydifferences.（）正確答案：BA.對(duì)B.錯(cuò)5【判斷題】(1分Awaytoimprovetheworkingspeedofpseudo-randomsequenceistoadoptMSRGstructure.（）正確答案：BA.錯(cuò)B.對(duì)第七章單元測(cè)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