第1页共11页编号：时间：2021年x月x日书山有路勤为径，学海无涯苦作舟页码：第1页共11页名词解释1．Explainthedifferencebetweenhardandsofthandoff.Answers：Thehardhandoffisthatwhenthesignalstrengthofaneighboringcellexceedsthatofthecurrentcell,plusathreshold,themobilestationisinstructedtoswitchtoanewfrequencybandthatiswithintheallocationofthenewcell.Thesofthandoffisthatamobilestationistemporarilyconnectedtomorethanonebasestationsimultaneously.Amobileunitmaystartoutassignedtoasinglecell.Iftheunitentersaregioninwhichthetransmissionsfromtwobasestationsarecomparable,themobileunitentersthesofthandoffstateuntilwhichitisconnectedtothetwobasestations.2．WhatarethecorestechniquesofWCDMA?Answers:TheWCDMAkeytechniquesmostlyconsistofthepowercontroltechnique,PNcodetechnique,RSKE,SoftHandoff,andSpeechcoding.3．Whatisattenuation?4．Whattwofunctionsareperformedbyanantenna?5．WhataretheadvantagesofusingCDMAforacellularnetwork?Answers:(1)Frequencydiversity;(2)Multipathresistance;(3)Privacy;(4)Gracefuedegradation.6.Whatarethekeydifferencesbetweenfirstandsecondgenerationcellularsystem?Answers:Thekeydifferencesbetweenthetwogenerations:(1).Digitaltrafficchannels;(2).Encryption;(3).Errordetectioncorrection;(4).Channelaccess.7.WhatarethecorestechniquesofTD-SCDMA?Answers:ThecorestechniquesofTD-SCDMAaresmartantenna(intelligentantenna),jointexaminationtechnique,SCDMAtechnique,softwarewirelesstechnique,anddynamicchannelallocationtechnique8.Whatisdirectbroadcastsatellite(DBS)?第2页共11页第1页共11页编号：时间：2021年x月x日书山有路勤为径，学海无涯苦作舟页码：第2页共11页Answers:Thesatellitevideosignalsaretransmissiondirectlytothehomeuser.9.Whatisanisotropicantenna?Answers:Anisotropicantennaisapointinspacethatradiatespowerinalldirectionequally.10.WhatisCDMA?Answers:CDMAisamultiplexingtechniqueusedwithspreadspectrum11.Whatisfrequencyhoppingspreadspectrum?Answers:Thesignalisbroadcastoveraseeminglyrandomseriesofradiofrequency,hoppingfromfrequencytofrequencyatfixedintervals12．Whataretheprimarycausesofatmosphericattenuationforsatellitecommunications?Answers:Theprimarycausesofatmosphericattenuationareoxygenandwater13．WhatisaSIR?Answers:Thisratioisdefinedtobetheratioofthedesiredaveragesignalpoweratareceivertothetotalaverageinterferencepower.14．WhatarefeaturesofCDMA?Answers:(1)Highspectrumefficiency(2)Releasefromfrequencymanagement(3)Lowmobilestationtransmitpower(4)Soft-handover(5)PathDiversity(RAKEFingers)(6)Security(7)Anti-jammingcapability15．Ingeneral,physicalmodelsincludethreebasicmodesofpropagation.Answers：（1）Free-spaceorlink-of-signaltransmission;（2）Reflection；（3）Diffraction.16．Intime,asmorecustomersusethethesystem,trafficmaybuildupsothattherearenotenoughfrequencybandsassignedtoacelltohandleitscalls.Anumberofapproacheshavebeenusedtocopewiththissituation,includingthefollowing。Answers:(1)Addingnewchannels；(2)Frequencyborrowing；(3)Cellsplitting；(4)Cellsectoring；(5)Microcells。17．Explainthedifferencebetweenopen-loopandclosed-looppowercontrol.Answers:Open-looppowercontroldependssolelyonthemobileunit,withnofeedbackfromtheBS.第3页共11页第2页共11页编号：时间：2021年x月x日书山有路勤为径，学海无涯苦作舟页码：第3页共11页Closed-looppowercontroladjustssignalstrengthinthereversechannelbasedonsomemetricofperformanceinthatreversechannel.18．Definechannelcapacity.Answers:Themaximumrateatwhichdatacanbetransmitte...
