第1題Inlearningthecourse,weassumethelearnerhasthefundamentalknowledgeofmodulation,channelcodingandsynchronization,whichiscoveredinCommunicationPrinciples第1題WhatarethemainproblemsofthefirstgenerationWlan?

A

poorperformanceBsecurityproblemsChighcostDfastdatarate正確答案：ABChomework1.3第1題Themainchallengesofwirelesscommunicationscomefromthe___betweenthetransmitterandreceiver.AmodulationanddemodulationdesignBchannelCspectrumallocationDdopplerhomework1.4第1題Inthefollowingdescriptiononthecellconcept，whichisincorrect?AThegeographicregionisdividedintocellsandthesecellsarenonoverlapping.BThechannelsetssuchasfrequencies/timeslots/codescanbereusedatspatially-separatedlocations.CShrinkingthecellsizecanincreasethecapacity.DThebigcellsizemaycausefrequenthandoffproblems.homework1.5第1題Bluetoothisaopenwirelesstechnologystandardforexchangingdataovershortdistances，whichcoveragecanbeextendedto1km.Testforchapter1第1題ThefirstwirelesscommunicationnetworksinthePre-industrialagetransmittedinformationbyusingsomesimplesignals,suchlike__signals,__signal,signal___,orbeatingdrums.

AsmokeBfireCflaresDlaser正確答案：ABC第2題ThemobiletelephonenetworkinNewYorkcouldonlysupportsmallnumberofsubscribersmainlybecausethepowerofthebasestationistoolow.

第3題ThefirstgenerationWLANdeviceshadtouselowpowerdensityschemebecausehighpowerdevicesareveryexpensive.第4題__isnotthereasonthatwhythe1stgenerationWLANisnotwidelyused.ALackofmobilityBLowdatarateCShortcoverage.DLackofstandardization第5題

-__

and__

aretwomaindisadvantagesforhighaltitudeorbitssatellitecommunications.

AHighpathlossBsallcoverageCbigpropagationdelayDmultpathinterferrence正確答案：AChomework2.1第1題Whatarethemainmechanismsbehindelectromagneticwavepropagation?AreflectionBdiffractionCpolarizationDscattering正確答案：ABDhomework2.2第1題Thefrequencybandisaprimaryfactortotakeintoaccountwhenassessingeffectivenessofradiocommunicationlinks.homework2.3第1題Scatteringoccurswhenthesurfaceoftheobjectbetweenthetransmitterandreceiverisirregularorcoarse.homework2.4第1題TheHatamodelisanotherempiricalmodelusingthegraphicalpathlossdataprovidedbyOkumura.Inwhatfrequencyrangeisiteffective?A150-1500MHzB180-1920MHzC200-2020MHzD240-2100MHzhomework2.5第1題TheminimumtransmissionqualityisnotcorrespondingtoaminimumSignal-to-NoisepowerRatio(SNR)atthereceiver.Testforchapter2第1題Whatcancausepowervariationinthereceivedsignaloverthedistance?Afree-spacepropagationBconstantsignalsourcepowerCpathlossDshadowingeffects正確答案：CD第2題Whichfrequencybandisusedfortelevisioncommunicationsandradionavigationsystems?A3kHz-30kHzB3MHz-30MHzC30MHz-300MHzD300MHz-3GHz第3題PathlossandShadowingaregenerallyreferredaslargescalepropagationeffects.第4題Fresnelknifeedgediffractionmodeliscommonlyuseddiffractionmodel.第5題Shadowingiscausedbytheamplificationofthepowerradiatedbythetransmitterandthereflectiveeffectsofthepropagationchannel.homework3.1第1題Inthetelephone/cablenetworksystem,whatisthecauseofthemultipathmechanism?AAtmosphericrefractionandreflectionBGroundandbuildingreflectionCReflectionsfromterminationsDMultimodepropagationhomework3.2第1題Themeandelayspread,rmsdelayspread,ordelayspreaddeviationcanbeusedtodescribethedelayspread,andtheseparameterscanbemeasureddirectly.homework3.3第1題Ifthebandwidthofthesignalisfargreaterthanchannelcoherencebandwidth,theeffectofDopplerspreadwouldbenegligibleandthechanneliscalledfastfadingchannel.homework3.4第1題Whenthetimespreadingisfarlessthanthesymboltime,thechannelissaidtobeflatfadingchannel.homework3.5第1題____and

____ofaRayleighfadingsignalaretwoimportantstatisticsandarekeyfactorsinthedesignofchannelcodesanddiversityschemesinmobilecommunications.AThelevelcrossingrateBAveragefadedurationCSignal-to-noiseratioDCarrierfrequency正確答案：ABTestforchapter3第1題Therearemanyphysicalfactorsintheradiopropagationenvironmentinfluencesmall-scalefading，suchas____.AMultipathpropagationBThesignalbandwidthCRelativemotionofthereceiverandtransmitterDRelativemotionofthereceiverandsurroundingobjects正確答案：ABCD第2題Foramodulatedsignal,ifthesignalbandwidthislessthanthechannelcoherencebandwidth,thesignalthatpassesthechannelwillexperience____.Afrequency-selectivefadingBflatfadingCRayleighfadingDmultipathfading第3題TherelativemotionbetweenthereceiverandthetransmitterresultinrandomfrequencymodulationduetodifferentDopplershiftsoneachofthemultipathcomponents.第4題Whenthechannelrmsdelayspreadismuchmorethanthesymbolduration,thechannelisregardedasfrequency-selectivefadingchannelorwidebandchannel.第5題Inthelinkbudgetofmobilecommunications,fademarginisnotnecessarilyconsidered.homework4.1第1題Thefollowingaresomeofthemainreasonswhydigitalmodulationswereintroduced.AHighordermodulationtechniquescanbeused.BPowerfulchannelcoding,equalizationormulticarriertechniquescanbeusedtomitigatetheISIeffect.CSpreadspectrumtechniquesmodulationscanbeusedtoremoveorcombinemultipath,resistinterference,anddetectmultipleuserssimultaneously.D

Encryptioncanalsobeapplied.正確答案：ABCDhomework4.2第1題Thefundamentalofdemodulationistoconverttheconstellationpointintoasignalvectorinthesignalspaceandfindthenearestconstellationpointtothisvector.

homework4.3第1題TheprobabilityoferrorassociatedwithconstellationsattheminimumdistancedminmultipliedbythenumberofneighborsatthisdistanceMdminis____.A

theupperboundB

thenearneighborapproximationCthelooserupperboundDtheexactsolution.homework4.4第1題In__,theinformationiscarriedinamplitude.AMPAMBMPSKCMQAMDMFSKhomework4.5第1題Inπ/4-DQPSK,thein-phaseandthequadrature-phasecomponentsoccuratatimedifferenceofT/2,whereTisthesymboltime,andthis

mitigatetheamplitudefluctuationsofa180degreephaseshift.

homework4.6第1題In__,theinformationiscarriedinphaseandamplitude.

AMPAMBMPSKCMQAMDMFSKhomework4.7第1題

ForMFSK,theminimumfrequencyseparationis__toguaranteethatthebasisfunctionsondifferentfrequencyareorthogonal.A2△f

c.=1/(2Ts)B

2△f

c.=1/TsC2△f

c.=0.5/TsD

△f

c.=1/Tshomework4.8第1題__donotsatisfytheheprincipleofpulseshapingthatinter-symbolinterference(ISI)betweenpulsesinthereceivedsignalisnotintroduced.

AThe

rectangularpulseBThecosinepulseCTheraisedcosinepulsesDThe

Gaussianpulsehomework4.9第1題Assumethatthesymbolenergyisdividedequallyamongallbits,ifGrayencoding

isusedandthesystemisunderareasonableSNRsandthesizeofsymbolsetisM,thenrs=rblog2Mandps.=pblog2M

homework4.10第1題__applieswhenTs≈Tc,whichmeanstheSNRpersymbolγsisroughlyconstantoverasymboltimesothatonecanintegratetheerrorprobabilityinAWGNoverthefadingdistributiontoobtaintheaverageerrorprobability.

ABERB

Theoutageprobability,PoutCTheaverageerrorprobabilityDTheoutageandaverageerrorprobabilitycombinedhomework4.11第1題TheirreducibleerrorforDPSKRayleighfadingchannelisapproximatedas0.5*(πfdTb)2.IftheDopplershiftisdetermined,alargebittime,orequivalently,alowerbitratecanguaranteealowererrorfloor.Testforchapter4第1題Thefollowingarecomponentsofthetransmitterofacommunicationsystem.AsourcecoderBchannelcoderCmodulatorDequalizer正確答案：ABC第2題Atreceiver,thelocaloscillator(LO)whichisgeneratedandtrackedbyacarrierfrequencyrecoverycomponentprovidesanunmodulatedsinusoidalsignal,toconverttheradiofrequencysignalintoabasebandsignal.第3題IfthereareMsymbolandeachsymbolhasKbits,i.e.M=2K.AssumethesymboldurationisT,thedatarateofthesystemis__.AM/TBK*TClog2M/TbpsDK/Tbps正確答案：CD第4題Indemodulation,minimizingthesymbolerrorprobabilitycorrespondstofindtheconstellationsithatmaximizesp(si|r),whereristhereceivedvector.第5題___are

performancecriteriawhichareusedtodescribetheperformanceofdigitalmodulationsoverfadingchannelsdependsontherateofchangeoffading.ABERBTheoutageprobability,PoutCTheaverageerrorprobabilityDTheoutageandaverageerrorprobabilitycombined正確答案：BCDhomework5.1第1題ForDiversity,theindependentpathsmaybeimplementedinthe_domain.

A

polarizationBtimeC

spaceD

frequency正確答案：BCDAhomework5.2第1題WhatisMaximalRatioCombining(MRC)?AAsystemthatcombinessignalsfrommultiplebranchesbyoptimallyweightingtheiramplitudesandphases.BAsystemthatonlyoutputsonebranchofsignalstothedemodulator.CAsystemthatswitchesbetweenbranchesbasedonRSSI.D

Asystemthatcombinessignalsfrommultiplebranchesbyequallyweightingthem.homework5.3第1題ChannelcodingreducethebandwidthefficiencyinhighSNRconditions.

homework5.4第1題Whatisthepurposeoftheparitycheckbitsinasystematiccode?

A

Toensurethatthecodewordisunique.B

Todetecterrorsinthecodeword.CToincreasethestorageefficiencyofthecode.DTomaptheinformationbitstothecodeword.homework5.5第1題Inthedecodingprocedureofblockcoding,thefirststepistocheckifareceivedcodewordisvalidornot.homework5.6第1題Theoutputofaconvolutionalencoderdependsonlyonthecurrentinputandnotonthepreviousinputs.homework5.7第1題Whichofthefollowingstatementsaboutblockcodingwithinterleavingistrue?A

Theinterleaverisappliedbeforethechannelencoder.BThebitsareputintothedemodulatorafterde-interleaver.CDe-interleaverisappliedafterdemodulator,theresultisthenputintothechanneldecoder.D)Theinterleaverisappliedafterthemodulator.DTheinterleaverisappliedafterthemodulator.homework5.8第1題Whatisthemainpurposeofequalizationinwirelesscommunications?(A)Toreducenoise(B)Toincreasesignalstrength(C)ToalleviateInterSymbolInterference(ISI)(D)ToimprovemodulationefficiencyAToreducenoiseBToincreasesignalstrengthCToalleviateInterSymbolInterference(ISI)DToimprovemodulationefficiencyhomework5.9第1題Thecomplexityoftimedomainequalizergrowasthedatarateincreases.Testforchapter5第1題_，_and_aretechniqueswhichcanbeusedtoimprovethelinkqualityofwirelesschannelsASourcecodingBDiversityCChannelcodingDEqualization正確答案：BCD第2題__selectsthebranchwiththehighestSNRastheresultdiversityoutputanddiscardsotherbranches.ASelectioncombiningBThresholdcombiningCMaximalRatiocombiningDEqualgaincombing第3題Whichofthefollowingstatementsistrueaboutchannelcoding?AItcanonlydetecterrors,notcorrectthem.BItcanonlycorrecterrors,notdetectthem.CItcanbothdetectandcorrecterrors.DIthasnoeffectonerrorcorrectioninwirelessfadingchannels.第4題Inthedecodingprocessofblockcoding,ifthesyndromevectorhasall-zeroentries,thereceivedcodewordisalwaysvalid.第5題Whatarethetwomaincategoriesoftimedomainequalization?ALinearandnonlinearBFrequencydomainandtimedomainCDecision-feedbackandmaximumlikelihoodsequenceestimationDSimpleandcomplexhomework6.1第1題ThefundamentalofspreadspectrumcommunicationcanbeexplainedbythefamousShannoncapacityformula.homework6.2第1題Forthepseudorandomsequenceinthespreadspectrumsystem,themostimportantthingisthecorrelationproperties,including:____.AautocorrelationBcrosscorrelationCpartialcorrelationDVariance正確答案：ABChomework6.3第1題Inspreadspectrumsystems,thestructureofmsequencegeneratorgenerallyhastwoforms:____and____.

ADSSSBMSRGCSSRGDFHSS正確答案：BChomework6.4第1題ARAKEreceiverisaclassicaldiversityreceiverdesignedfortheCDMAsystem.Testforchapter6第1題Inspreadspectrumcommunications,thesignalisspreadbyaPNcodeatthetransmitteranditiscorrelatedbythesamePNcodeatthereceiver,whichhasmanyadvantages,including:____.AStronganti-interferencecapabilityBStrongresistancetomultipathinterferenceCHighcapabilityofanti-fadingDLowprobabilityofinterception正確答案：ABCD第2題Toguaranteethespreadingcodegeneratedinthereceivercansynchronizewiththespreadingcodeinthereceivedsignal,____isneeded.AphasesynchronizationBfrequencysynchronizationCtimesynchronizationDpowersynchronization第3題Spreadspectrumcanbetakentoimproveperformanceofwirelesscommunications.第4題Spreadspectrumcommunicationisasingle-accesscommunicationmethodthatdistinguishescommunicationaddressesbyfrequencydifferences.第5題Awaytoimprovetheworkingspeedofpseudo-randomsequenceistoadoptMSRGstructure.homework7.1第1題WhatisthedifferencebetweentraditionalFDMandOFDMintermsofhowtheydividethefrequencyband?ATraditionalFDMdividestheentirefrequencybandintonon-overlappingsub-channels,whileOFDMdividesitintooverlappingsub-channelswithorthogonalcharacteristics.BTraditionalFDMdividestheentirefrequencybandintooverlappingsub-channels,whileOFDMdividesitintonon-overlappingsub-channels.C

TraditionalFDMdividesthefrequencybandintoequalparts,whileOFDMdividesitintounequalparts.

D

TraditionalFDMusescoherentdemodulation,whileOFDMusesnon-coherentdemodulation.homework7.2第1題WhatisthepurposeofaddingaguardintervalinanOFDMsystem?AToincreasethedatarateBToreducepowerconsumptionCTominimizeISIandmultipathinterferencecausedbydelayspreadofthechannelDToimprovesignalqualityhomework7.3第1題Whatisthetermusedtodescribemultipleantennasatbothtransmitterandreceiverinacommunicationsystem?AMultipleInputSingleOutput(MISO)BMultipleInputMultipleOutput(MIMO)CSingleInputSingleOutput(SISO)DSingleInputMultipleOutput(SIMO)homework7.4第1題WhatarethetwomainapplicationsofMIMOsystem?ASpatialmultiplexingandspatialdiversityBTimemultiplexingandfrequencydiversityCFrequencymultiplexingandtimediversityDChannelmultiplexingandsignaldiversityhomework7.5第1題Whenthenumberofantennaelementstendstobeverylarge(infinite),whathappenstothechannelsofMassiveMIMO?ATheybecomemorerandom.BTheybecomelesscertain.CTheytendtobeorthogonal.DTheybecomemorecertain.TestforChapter7第1題Whatisthepurposeofmulticarriermodulation?ATodivideahighspeeddatastreamintomanylowspeedsubstreamsBToimprovetheperformancethroughdiversityCTochangefrequencyselectivefadingintoflatfadingDToovercomeDopplershiftproblem正確答案：ABC第2題WhereisthecyclicprefixaddedinanOFDMsystem?ABeforetheOFDMsignalissenttothechannelfortransmissionBAftertheOFDMsignalisreceivedatthereceiverCDuringtheDFTdemodulationprocessDBeforetheIDFTmodulationprocess第3題WhatisthematrixHusedtorepresentinaMIMOchannelmodel?AThecomplexgainfactorfromeachtransmitantennatoreceiveantennapairBThechannelgainfromeachtransmitantennatoreceiveantennapairCThenumberoftransmittingandreceivingantennasinaMIMOsystemDTheestimatedaccuracyofthechannelatthereceiver第4題WhenboththereceiverandtransmitterknowtheCSI,howcanthecorrespondingpowerallocationpolicybeobtainedforthemaximumchannelcapacity?AItisobtainedbyaveragingthepowerallocationonthetransmittingantenna.BItisobtainedbyusingwaterfillingalgorithm.CItisobtainedbyequallyallocatingthepowerPi.DItisobtainedbyusingSVD.第5題WhatisthemainideaofspatialdiversityinMIMO?AToincreasethereliabilityofcommunicationbyusingspatialredundancytotransmitdatacontainingthesameinforma