2025年无线通信专业题库

名词解释

1.Explainthedifferencebetweenhardandsofthandoff.

Answers：Thehardhandoffisthatwhenthesignalstrengthofaneighboringcell

exceedsthatofthecurrentcell,plusathreshold,themobilestationisinstructedto

switchtoanewfrequencybandthatiswithintheallocationofthenewcell.

Thesofthandoffisthatamobilestationistemporarilyconnectedtomorethanone

basestationsimultaneously.Amobileunitmayscanoutassignedtoasinglecell.If

theunitentersaregioninwhichthetransmissionsfromtwobasestationsare

comparable,themobileunitentersthesofthandoffstateuntilwhichitisconnectedto

thetwobasestations.

2.WhatarethecorestechniquesofWCDMA?

Answers:TheWCDMAkeytechniquesmostlyconsistofthepowercontrol

technique,PNcodetechnique,RSKE,SoftHandoff,andSpeechcoding.

3.Whatisattenuation?

4.What(wofunctionsareperformedbyanantenna?

5.Whatare(headvantagesofusingCDMAforacellularnetwork?

Answers：(1)Frequencydiversity;(2)Multipathresistance;(3)Privacy;(4)Gra^efue

degradation.

6.Whatarethekeydifferencesbetweenfirstandsecondgenerationcellularsystem?

Answers:Thekeydifferencesbetweenthetwogenerations:

(1).Digitaltrafficchannels;(2).Encryption;(3).Errordetectioncorrection;

(4).Channelaccess.

7.WhatarethecorestechniquesofTD-SCDMA?

Answers:ThecorestechniquesofTD-SCDMAaresmartantenna(intelligentantenna),joint

examinationtechnique,SCDMAtechnique,softwarewirelesstechnique,anddynamicchannel

allocationtechnique

8.Whatisdirectbroadcastsatellite(DBS)?

Answers:Thesatellitevideosignalsaretransmissiondirec:lytothehomeuser.

9.Whatisanisotropicantenna?

Answers:Anisotropicantennaisapointinspacethatradiatespowerinalldirectionequally.

10.WhatisCDMA?

Answers:CDMAisamultiplexingtechniqueusedwithspreadspectrum

11.Whatisfrequencyhoppingspreadspectrum?

Answers:Thesignalisbroadcastoveraseeminglyrandemseriesofradiofrequency,hopping

fromfrequencytofrequencyatfixedintervals

12.Whataretheprimarycausesofatmosphericattenuationforsatellitecommunications?

Answers:Theprimarycausesofatmosphericattenuationareoxygenandwater

13.WhatisaSIR?

Answers:Thisratioisdefinedtobetheratioofthedesiredaveragesignalpowerat

areceivertothetotalaverageinterferencepower.

14.WhatarefeaturesofCDMA?

Answers:(l)Highspectrumefficiency(2)Releasefromfrequencymanagement

(3)Lowmobilestationtransmitpower(4)Soft-handover(5)PathDiversity(RAKE

Fingers)(6)Security(7)Anti-jammingcapability

15.Ingeneral,physicalmodelsincludethreebasicmodesofpropagation.

Answers：(1)Free-spaceorlink-of-signaltransmission;(2)Reflection：(3)Diffraction.

16.Intime,asmorecustomersuse(hethesystem,trafficmaybuildupsothattherearenot

enoughfrequencybandsassignedtoacelltohandleitscalls.Anumberofapproacheshavebeen

usedtocopewiththissituation,includingthefollowing。

Answers:(l)Addingnewchannels；(2)Frequencyborrowing；(3)Cellsplitting；

(4)Cellsectoring；(5)MicrocellSo

17.Explainthedifferencebetweenopen-loopandclosed-lcoppowercontrol.

Answers:Open-looppowercontroldependssolelyonthemobileunit,withno

feedbackfromtheBS.

Closed-looppowercontroladjustssignalstrengthinthereversechannelbasedon

somemetricofperformanceinthatreversechannel.

18.Definechannelcapacity.

Answers:Themaximumrateatwhichdatacanbetransmittedoveragiven

communicationpath,orchannel,undergivenconditionsisreferredtothechannel

capacity.

填空题

1.Antennacharacteristicsareessentiallythesamewhetheranantennaissending

orreceivingelectromagneticenergy.

2.Thebasisforanalogsignalingisaconthiuousconstantfrequencysignalknownasthe

carriersignal.

3.NikolaTeslainventedthewirelesstelegraphin1893.

4.Atransmissionfromearthstationtosatelliteisreferredtoasuplinkinthesatellite

communication.

5.Theessenceofacellularnetworkistheuseofmultiplelow-powertransmitters,onorder

of100Worless.

6.ThirdgenerationsystemgenerallycallWTDMAorUMTS.

7.Adjacentcellsarcassigneddifferentfrequenciestoavoidinterferenceorcrosstalk.

8.Viewedasafunctionof,anelectromagneticsignalcanbeeitheranalogordigital.

Ananalogsignalisoneinwhichthesignalintensityvariesinasmoothfashionovertiire.

9.Thedatasignalingrate,orjustdatarate,ofasignalistherate,inbitspersecond,thatdata

aretransmitted.

1OTheTD-SCDMAisamultipleconnectintoincludetheFCDMA/TDMA/CDMA

1i.NikolaTeslainventedthewirelesstelegraphin1893.

12.Adigitalsignalisoneinwhichthesignalintensitymaintainsaconstantlevelforsome

periodoftimeand(henchangestoanotherconstantlevel.

13.Reflectionoccurswhenanelectromagneticsignalencountersasurfacethatislarge

relativetothewavelengthofthesignal.

14.Ifthesizeofanobstacleisontheorderofthewavelengthofthesignalor

lessscatteringoccurs.

15.ForadataofR,thedurationofabitisT=—secondsandthedurationofasignalelement

isTs=LTseconds.IfTcisgreaterthenortoTs,thespreadingmodulationisreferredtoas

slow-freaucncv-hopspreadspectrum;otherwiseitisknownasfast-frraucncy-hopspread

spectrum.

16.Atransmissionfromsatellitestationtoearthisreferredtoasdownlinkinthesatellite

communication.

17.Thecellssufficientlydistantfromeachothercanusethesamefrequencyband

18.Codedivisionmultipleaccessisaspreadspectrumbasedtechniqueformultiplexing.

19.Theobjectiveofthethirdgenerationofwirelesscommunicationistoprovidefairlyhighspeed

wirelesscommunicationstosupportmultimedia,data,andvideoinadditiontovoice.

20.PowercontroltechniqueiscoreintheCDMA.

21.Onepurposeofthedata-layeristoperforinerrorcorrectionordetection.

22.Thechannelprovidesthephysicalmeansfortransportingthesignalproducedbythe

transmitteranddeliveringittothereceiver.

24.Thekeyphysicalresourceistheradiospectruminwirelesssystem.

24.Adigitalsignalisoneinwhichthesignalintensitymaintainsaconstantlevelforsome

periodoftimeandthenchangestoanotherconstantlevel.

25.Thefrequencyistherateatwhichthesignalrepeats.

26.Anantennathattransmitsequallyinalldirectionscalledtheisotropicradiatiu.

27.Noisecanbedefinedasunwantedeleclricalsignalsinterferencewiththedesired

signal.

28.Thebasicideawithcellularsystemistoreusechannelindifferentcell,increasingthe

capacity

29.Duringtheperiodfrom1895to1901.GuglielmoMarconidevelopedanapparatusfor

transmittingradiowavesoverlongerdistances.

30.Anelectromagneticsignalcanbeeitheranalogordigital.Ananalogsignal

isoneinwhichthesignalintensityvariesinasmoothfashionovertime.

31.Thespectrumofasignalistherangeoffrequenciesthatitcontains.

1.32.Thesamefrequencyassignmentscannotbemadeinadjacentcellbecauseof

inter-channelinterference.

33.Handoffmaybenetworkinitiated.

34.ThateachuseroccupiesacyclicallyrepeatingtimeslotintheTDMAsystem.

35.AllusersinaCDMA、usethesamecarrierfrequencyandmaytransmitsimultaneously.

36.Self-jammingisaprobleminCDMAsystem.

37.TheGSMkeytechniqueconsistofeightparts

38.Reflectionoccurswhenanelectromagneticsignalencountersasurfacethatislargerelative

tothewavelengthofthesignal.

判断题

I.Thermalnoisecanbeeliminated.(N)

2.Thetime-selectivechannelsaretime-invariantchannels.(N)

3.AhighSNRwillmeanahigh-qualitysignal.(Y)

4.Free-spacepropagation,inwhichthereceivedpowerdecreasesasthesquareofthedistance

fromthetransmitter.(Y)

5.Fastfadingistherapidvariationofsignallevelswhentheuserterminalmovesshortdistances.

(Y)

6.Trafficchannelsareusedtoexchangeinformation.(N)

7.Multipleaccessschemesareusedtoallowmanymobileuserstosharesimultaneouslyafinite

amountofradiospectrum.(Y)

8.Directsequencemultipleaccessisalsocalledcodedivisionmultipleaccess(CDMA).

(Y)

9.ThemostpopularsecondgenerationstandardsincludethreeTDMAstandardsandoneCDMA

standard.(Y)

10.TheNScontrolshandoffbetweencellindifferentBSSs,authenticatesusersandvalidatestheir

accounts,andincludesfunctionsforenablingworldwideroamingofmobileusers.

(Y)

11.Thermalnoisecannotbeeliminated.(Y)

12.Frequency-SelectiveChannelsistime-invariantchannels.(N)

13.Thegreater(hebandwidth,(hehighertheinformation-carryingcapacity..(Y)

14.Reflection,wherein,fortheplane-Earthmodel,thereceivedpowerdecreasesasthefourth

powerofdistance.(Y)

15.Slowfadingarisesfromthefactthatmostofthelargereflectorsanddiffractingobjectsalong

thetransmissionpatharedistantfromtheterminal.(Y)

16.Controlchannelsareused(oexchangeinformation.(Y)

17.ThateachuseroccupiesacyclicallyrepeatingtimeslotintheFDMAsystem.(N)

18.ManyusersofaCDMAsystemsharethesametime-slot.(N)

19.LikeTDMAorFDMA,CDMAhasasoftcapacitylimit..(N)

20.TheNScontrolshandoffbetweencellindifferentBSSs,authenticatesusersandvalidatestheir

accounts,andincludesfunctionsforenablingworldwideroamingofmobileusers.

(Y)

选择题

Foreachsentencethereare(burchoices.ChoosetheONEanswerthatbestcompletesthe

sentence.

1.Ageneralsinewavecanberepresentedbythreeparameters,theyare(A).

A.peakamplitude,frequency,andphase;B.speed,frequency,andphase;

C.peakamplitude,speed,andphase;D.peakamplitude,frequency,andspeed.

2.Transmissionmediacanbeclassifiedas(C).

A.guided;B.unguided;C.guidedandunguided;D.wiredandwireless.

3.Fadingeffectsinamobileenvironmentcanbeclassifiedaseither(A).

A.fastorslow;B.fastandslow;C.fast;D.slow.

4.(D)istheprocedureforchangingtheassignmentofamobileunitfromoneBStoanother

asthemobileunitmovesfromonecelltoanother.

A.Transmission;B.change;C.divert;D.Handoff;

5.TheboundariesatUm,Abis,andArefertointerfacesbetweenfunctionalelementsthatarc

standardizedinthe(B)documents.

A.AMPS;B.GSM;C.GPRS;D.CDMA.

6.WhichofthefollowingisnotcoretechniqueoftheCDMA?(A)

A.Powercontrol;B.PNcode;C.RAKE;D.transfers.

7.GSMkeytechniqueconsistof(C)parts.

A.6;B12;C.8;D.10.

8.TheGSMspectralallocationis25MHzforbasetransmission(D)and25MHzforir.obile

transmission(890—915MHz).

A.1805—1880MHz;B.1710—1785MHz;C.890—915MHz;D.935—960MHz.

9.Thirdgenerationsystemmostlycomprisethe(A).

A.RANandCN;B.MSandBS;C.MSandCN;D.RANandBS.

10.Thecellularmobilecommunicationsystemconsistofthreeparts,theyare(B)

A.TDMA,FDMAandCDMA;B.BS,NSandMS;

C.CDMA,WCDMAandCDMA;D.FDD,TDDandFHSS.

11.Thereisdirectrelationshipbetweentheinformation-cardingcapacityofasignaland

bandwidth:(D)

A.Thenarrowthebandwidth,thelow(heinformation-carryingcapacity;

B.Thegreaterthebandwidth,thehighertheinformation-carryingcapacity;

C.Thenarrowthebandwidth,thelowtheinformation-carryingcapacity;

D.Thenarrowthebandwidth,thehighertheinformation-carryingcapacity;

12.Twotechniquesformultiplexingintelecommunicationsnetworkareincommonuse,theyare

(D).

A.CDMAandTDMA;B.FDMAandTDMA;FDMAandCDMA;D.TDMandFDM.

13.Fordirectsequencespreadspectrum(DSSS),eachbitintheoriginalsignalisrepresentedby

multiplebitsinthetransmittedsignal,usinga(B).

A.code;B.spreadingcode;C.FHSS;D.DSSS.

14.ThenumberofsubchannelsprovidewithinasatellitechannelviaFDMAislimitedby(C)

factors.

A.Thermal;B.Intcrmcdulationnoise;C.Thermal,IntermodulationnoiseandCrosstalk;

D.Crosstalk;

15.Cellularsystemusethetwokindsofpowercontrol,theyare(A).

A.Open-looppowercontrolandclosed-looppowercontrol;B.MSandBS;

C.Open-looppowercontrolandMS;D.closed-looppowerandcontrol.

16.Amobilestationcommunicationacrossthe(C)interface,alsoknownastheairinterface.

A.Abis;B.A;C.Um;D.lu.

17.WhichofthefollowingisnotcoretechniqueoftheWCDMA?(A)

A.Transfers;B.PNcode;C.RAKE;D.Powercontrol.

18.WhichofthefollowingiscoretechniqueoftheTD-SCDMA?(B)

A.Transfers;B.Smartantennas;C.Encoding;D.Errorcontrol.

19.TheGSMspectralallocationis25MHzforbasetransmission(935—960MHz)and25MHzfor

mobiletransmission(D).

A.935—960MHz;B.1805—1880MHz;C.1710—1785MHz;D.890—915MHz.

20.Thirdgenerationsystemmostlycomprisethe(A).

A.UTRAN,CNandUE;B.MS,MSCandBS;C.MS,RANandCN;D.RAN,CNandBS.

21.Abasestationsubsystem(BSS)consistsof(B).

A.abasestation;B.abasestationcontrollerandoneormorebasetransceiverstations;

C.abasestationcontrollerandaradioantenna;D.oneormorebasetransceiverstations.

22.Fadingeffectsinamobileenvironmentcanbeclassifiedaseither(D).

A.fastorslow;B.fastandslow;C.fast;D.slow.

23.(D)istheprocedureforchangingtheassignmentofamobileunitfromoneBStoanother

asthemobileunitmovesfromonecelltoanother.

A.Transmission;B.change;C.divert;D.Handoff.

24.Fastfadingisduetoreflectionsoflocalobjectsandthe(D)oftheterminalrelativeto

thoseobjects.

A.multipath;B.environment;C.largereflectors;D.motion.

25.Thirdgenerationsystemmostlycomprisethe(A).

A.RANandCN;B.MSandBS;C.MSandCN;D.RANandBS.

26.Thecellularmobilecommunicationsystemconsistofthreeparts,theyare(B).

A.TDMA,FDMAandCDMA;B.BS,NSandMS;C.CDMA,WCDMAandCDMA;

D.FDD,TDDandFHSS.

27.Secondgenerationstandardsusedigitalmodulationformatsand(A)andCDMA/FDD

multipleaccesstechniques.注意；A和B答案相似

A.TDMA/FDD;B.TDMA/FDD；C.SCDMA/FDD；D.TDMA/TDD

28.Twotechniquesformultiplexingintelecommunicationsnetworkareincommonuse,theyare

(D).

A.CDMAandTDMA;B.FDMAandTDMA;C.FDMAandCDMA;

D.TDMandFDM.

29.AGSMcellcanhavearadiusofbetween(B),dependingontheenvironment.

A.100mand5km

B.100mand35km;

C.100mand50km;

D.100mand100km.

30.Asageneralruleofthumb,wemustkeepthe"(A)Fresnelzone"freeofobstructionsin

ordertoobtaintransmissionunderfrcc-spaccconditions.

A.first;B.secondly;C.thirdly;D.fourthly.

31.Thermalnoi