IT专业英语UNIT19 3G Network.ppt

UNIT193GNetwork,19-1TechnicalPart19-2ReadingMaterial,19-1TechnicalPart19-1-1Definition3Gor3rdgenerationmobiletelecommunicationsisagenerationofstandardsformobilephonesandmobiletelecommunicationservicesfulfillingtheInternationalMobileTelecommunications-2000(IMT-2000)specificationsbytheInternationalTelecommunicationUnion.Applicationservicesincludewide-areawirelessvoicetelephone,mobileInternetaccess,videocallsandmobileTV,allinamobileenvironment.,19-1-2IntroductionsSeveraltelecommunicationscompaniesmarkethaveextendedtowirelessmobileInternetservicesas3G,indicatingthattheadvertisedserviceisprovidedovera3Gwirelessnetwork.Servicesadvertisedas3GarerequiredtomeetIMT-2000technicalstandards,includingstandardsforreliabilityandspeed(datatransferrates).,TomeettheIMT-2000standards,asystemisrequiredtoprovidepeakdataratesofatleast200kbit/s(about0.2Mbit/s).However,manyservicesadvertisedas3Gprovidehigherspeedthantheminimumtechnicalrequirementsfora3Gservice.Recent3Greleases,oftendenoted3.5Gand3.75G,alsoprovidemobilebroadbandaccessofseveralMbit/stosmartphonesandmobilemodemsinlaptopcomputers.,1.ConceptofUMTSTheUMTS(UniversalMobileTelecommunicationsSystem)firstofferedin2001,standardizedby3GPP,usedprimarilyinEurope,Japan,China(howeverwithadifferentradiointerface)andotherregionspredominatedbyGSM2Gsysteminfrastructure.ThecellphonesaretypicallyUMTSandGSMhybrids.Severalradiointerfacesareoffered,sharingthesameinfrastructure:ThelatestUMTSrelease,HSPA+,canprovidepeakdataratesupto56Mbit/sinthedownlinkintheory(28Mbit/sinexistingservices)and22Mbit/sintheuplink.Thefollowingstandardsaretypicallybranded3G:,TheTD-SCDMA(TimeDivisionDuplexSynchronousCodeDivisionMultipleAccess)radiointerfacewascommercializedin2009andisonlyofferedinChina.Thesystembandwidthis1.6MHz,chiprateis1.28Mbps.TD-SCDMAisanimportantfeatureof3GPPR4standardsandadmittedtotheUTRATDDstandardby3GPPin1999.,TheoriginalandmostwidespreadradiointerfaceiscalledW-CDMA(WidebandCodeDivisionMultipleAccess).Thesystembandwidthis5MHz,chiprateis3.84Mbps.TheFigure19-1showsthenetworkarchitectureofWCDMA.,Figure19-1ThenetworkarchitectureofWCDMAtelecommunicationsindustry,TheCDMA2000system,firstofferedin2002,standardizedby3GPP2,usedespeciallyinNorthAmericaandSouthKorea,sharinginfrastructurewiththeIS-952Gstandard.ThecellphonesaretypicallyCDMA2000andIS-95hybrids.ThelatestreleaseEVDORevBofferspeakratesof14.7Mbit/sdownstream.TheFigure19-2showsthedeploymentofCDMA20001XEVDO.,Figure19-2NetworkdeploymentofCDMA20001XEVDO,Theabovesystemsandradiointerfacesarebasedonspreadspectrumradiotransmissiontechnology.WhiletheGSMEDGEstandard(“2.9G”),DECT(DigitalEnhancedCordlessTelecommunication)cordlessphonesandMobileWiMAXstandardsformallyalsofulfilltheIMT-2000requirementsandareapprovedas3GstandardsbyITU,thesearetypicallynotbranded3G,andarebasedoncompletelydifferenttechnologies,2.IntroductionsofTD-SCDMATD-SCDMAstandard,developedbytheChinaindependently,hasbecomeoneofthethreemainstream3G,andhasanimportantpositioninChinaorevenininternational,TD-SCDMAusesTDD,smartantenna,jointdetection,dynamicchannelallocation,uplinksynchronization,batonhandoverandotherkeytechnologies.AllofthesehaveTF-SCDMAsystemperformancebeengreatlyimproved,thefollowingwilldescribeeachofthekeytechnologyofTD-SCDMA.,IntroductionstoTDD3Gsystemisdividedintotimedivisionduplex(TDD)andfrequencydivisionduplex(FDD)modes.FDDisusedinWCDMAandCDMA2000,datasreceivingandtransmissionoccurintwosymmetric,separatedfrequencychannel.TDDisusedinTD-SCDMA,whichmeansthereceivingandtransmissionoccurinthesamefrequency.,Throughperiodicconversiondirection,alternationuplinkanddownlinktransmissioninthesamecarrier,withaguaranteedtimetoseparatethereceivingandtransmissionchannel.TD-SCDMAsystemisdividedintotheCoreNetwork,RadioAccessNetworkandUserEquipmentfromthefunctions.ThedesigncombinewithFDMA,TDMA,CDMAandSDMAasawhole,hashighspectrumefficiencyandlowemissionpower.,Theuplinkanddownlinkcanbeasymmetricisalsoitsadvantage.TD-SCDMAmaintainbackwardcompatibilitywithGSM,whichisthesecondgenerationmobilecommunicationsystemcurwidelyusedinChinaandtheworld,allowingsmoothtransitionfromGSMto3Gsystems.,AdvantageofTDD:1)Nosymmetricband.ItcanusetheasymmetricbandflexiblywhichFDDcantuse.Itcanadjustthenumberofupanddowntimeslotstosupportasymmetricdatasevices.2)Uplinkanddownlinkhasthesamefrequency,sothepropagationcharacteristicscanbeconsideredthesameundercertainconditions.Itsbeneficialusingsmartantennasandothernewtechnologies.3)EquipmentcostsaregenerallylowerthantheFDDsystem.,3.AdvantagesanddisadvantagesofTD-SCDMAAdvantages1)Highspectrumefficiency,TD-SCDMAusesTDDmode,applicateFDMA,CDMA,TDMAmultipleaccesstechnologiessynthetically,tofacilitatesetuplingkanddownlinkswitchpointinthetransmissionfordifferentkindsofservices,thusincreasingspectrumefficiency.,2)Supportavarietyofcommunicationinterfaces:TD-SCDMAmeetavarietyofinterferencerequirementsincludelub,A,Gb,Iu,IuR.Basestationsubsystemcanbebothasaexpansionof2G,2.5GGSMandabasestationsubsystemof3G.,3)Spectrumflexibility:TD-SCDMAhasaflexiblefrequencyspectrum.Onlyabandof1.6Mcanprovidetheserviceof3Gwith2Mspeed,whichisveryidealforthetransmissionofasymmetricoperations.4)Systemperformancestable:TD-SCDMAismoresuitablefortheemergingsmartantennatechnologyandjointdetectiontechnology.Allofthesetechnologiescanreduceinterferenceandincreasethestabilityofsystem.,5)Compatibilitywithlegacysystems:ItadapttoavarietyofUEs(UserEquipment)oftheenvironment,canimplementasmoothtransitionfromexistingcommunicationssystemtothenextgenerationmobilecommunicationsystem.,Disadvantage1)TD-SCDMAisfallingbehindWCDMAandCDMA2000incommercialprogress,technologicaldevelopmentandindustrialscale.TD-SCDMAhasanarrowbandwidthandcannottakefulladvantageofmultipath,whichreducethesystemefficiency.2)Abilityinhigh-speedmobileenvironmentisfallingbehindWCDMAandCDMA2000.3)TD-SCDMAsystemrequiresdistrictkeepsynchronously,whichneedprecisetiming.Sothereisahighrequirementonthetimingsystem.,19-1-3ApplicationCaseorExample1.Case1:ApplicationinstreammediaserviceWCDMAequipmentsupportingstreammediabusiness,whichsupportsthestandardRTP/RTCPprotocol,providesthehighperformanceadaptivebandwidthandtheindustryswidelyusedMPEG-2/4technologies,alsoappliedtoaudio,videocodec,andprovideawealthofoperationalinterface,accesstovarioustypesofmedia.,Itcansupportunicast,multicastserviceandvarietychargingpolicywithstreammediatechnology,providingacompletedigitalrightsmanagement.Figure19-3showslogicalnetworkdiagramofstreammediaasbelow.,Figure19-3Logicalnetworkdiagramofstreammedia,HTTPAccelerator:Webbrowsingisthemostwidelyuseddataservice.Usersexpecttobeabletoquicklyloadwebpagesatanytimeorplace.Intraditionalmobiletelecommunicationsystems,however,multipleservicescoexistandequallycompeteforlimitedbandwidthresources.Bandwidthisnotallocatedpreferentiallytowebpageaccess,makingitdifficultforuserstoenjoyhigh-quality,low-delaywebbrowsing.Duringhigh-traffichours,webaccessisfrequentlyimpactedbyotherservicesandusersexperiencehighlevelsofdelay.,Thisfeaturereliesonpacketanalysistorecognizewebpageaccessesandthenpreferentiallyallocateshigherbandwidthtotheseservices,thusreducingaccesstimeandimprovingtheuserexperience.ThisfeatureisonlyapplicableforHSDPAusers.,P2PSlowdown:Withthecurrentrapidgrowthofhighbandwidthmobiletelecommunicationsystems,moreandmoreusersareusingP2Ptodownloadcontentsuchasmusicandvideos.Duetoitshighvolumeandlongduration,P2Ptrafficconsumesalargeamountofsystemresources.Thissignificantlyincreasesoperatorcostsandadverselyaffectstheuserexperienceofothertimesensitiveservices.Therefore,tosolvethisproblem,thisfeatureisintroduced.,ThebelowFigure19-4showstheHTTPAcceleratorandP2PDownloadRateRestriction.ThisfeaturerestrictsP2Ptrafficduringbusyperiods,reducingoperatorcostandimprovingtheuserexperienceofothertimesensitiveservices.High-speedP2Pdownloadsarenotrestrictedduringidleperiods,whichallowsP2Puserstoachievegoodperformanceandhelpsuserstakeadvantageofnetworkresources.,Figure19-4HTTPAcceleratorandP2PDownloadRateRestriction,19-2ReadingMaterial19-2-1ReadingComprehensionIntroductionto3GTheInternationalTelecommunicationsUnion(ITU)definedthethirdgeneration(3G)ofmobiletelephonystandardsIMT-2000tofacilitategrowth,increasebandwidth,andsupportmoredevicesapplications.Forexample,GSM(thecurrentmostpopularcellularphonestandard)coulddelivernotonlyvoice,butalsocircuit-switcheddataatdownloadspeedsupto14.4kbps.Buttosupportmobilemultimediaapplications,3Ghadtodeliverpacket-switcheddatawithbetterspectralefficiency,atfargreaterspeeds.,InternationalMobileTelecommunications-2000(IMT-2000),betteras3Gor3rdGeneration,isafamilyofstandardsforwirelesscommunicationsdefinedbytheInternationalTelecommunicationsUnion,whichincludesGSMEDGE,UMTS,andCDMA2000aswellasDECTandWiMAX.Servicesincludewide-areawirelessvoicetelephone,videocalls,andwirelessdata,allinamobileenvironment.Comparedto2Gand2.5Gservices,3Gallowssimultaneoususeofspeechanddataservicesandhigherdatarates(upto14.4Mbit/sonthedownlinkand5.8Mbit/sontheuplinkwithHSPA+).,Thus,3Gnetworksenablenetworkoperatorstoofferusersawiderrangeofmoreadvancedserviceswhileachievinggreaternetworkcapacitythroughimprovedspectralefficiency.Both3GPPand3GPP2arecurrentlyworkingonfurtherextensionsto3Gstandards,namedLongTermEvolutionandUltraMobileBroadband,respectively.Beingbasedonanall-IPnetworkinfrastructureandusingadvancedwirelesstechnologiessuchasMIMO,thesespecificationsalreadydisplayfeaturescharacteristicforIMT-Advanced(4G),thesuccessorof3G.However,fallingshortofthespeedrequirementsfor4G(whichis1Gbit/sforstationaryand100Mbit/sformobileoperation),thesestandardsareclassifiedas3.9GorPre-4G.3GPPplanstomeetth4GgoalswithLTEAdvanced,whereasQualcommhashalteddevelopmentofUMBinfavouroftheLTEfamily.,Words&ExpressionsInternationalTelecommunicationsUnion国际电信联盟facilityvt.使便利，减轻的困难GSM全球移动通信系统，俗称全球通EDGE是一种基于GAM/GPRS网络的数据增强型移动通信技术，通常被称为“2.75代技术”UMTS通用移动通信技术CDMA2000一种3G移动通信标准,DECT先进数字式无线通信系统WiMAX微波存取全球互通，是一项新型的宽带无线接入技术simultaneousadj.同时发生的，同时存在的uplink向上传输HSPA+是HSPA(3GPPR6)的向下演进版本，是上下行能力增强的技术,UMB是CDMA2000系列标准的演进升级版本LTE3GPP长期演进(LTE)项目，被看做准4G标准infrastructuren.基础设施，基础结构MIMO多输入多输出技术haltvt&vi.使停下来,19-2-2ExercisesI.MultipleChoices.1.Accordingtothepassage,3Grefersto_.A.3gamesB.3gradesC.3generationsD.3ndgenerations,2.About3G,whichofthefollowingisNOT