Wireless Communications（西安电子科技大学）知道智慧树章节答案

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