IT专业英语UNIT21 4G Network.ppt

UNIT214GNetwork,21-1TechnicalPart21-2ReadingMaterial,21-1TechnicalPart21-1-1Definition4Gisthefourthgenerationofcellphonemobilecommunicationsstandards.Itisasuccessorofthethirdgeneration(3G)standards.A4Gsystemprovidesmobileultra-broadbandInternetaccess,forexampletolaptopswithUSBwirelessmodems,tosmartphones,andtoothermobiledevices.Conceivableapplicationsincludeamendedmobilewebaccess,IPtelephony,gamingservices,high-definitionmobileTV,videoconferencingand3Dtelevision.,Two4Gcandidatesystemsarecommerciallydeployed:TheMobileWiMAXstandard(atfirstinSouthKoreain2006),andthefirst-releaseLongtermevolution(LTE)standard(inScandinaviasince2009).Ithashoweverbeendebatedifthesefirst-releaseversionsshouldbeconsideredas4Gornot.Seetechnicaldefinition.IntheU.S.,SprintNextelhasdeployedMobileWiMAXnetworkssince2008,andMetroPCSwasthefirstoperatortoofferLTEservicein2010.USBwirelessmodemshavebeenavailablesincethestart,whileWiMAXsmartphoneshavebeenavailablesince2010andLTEsmartphonessince2011.Equipmentmadefordifferentcontinentsarenotalwayscompatible,becauseofdifferentfrequencybands.MobileWiMAXandLTEsmartphonesarecurrently(April2012)notavailablefortheEuropeanmarket.,21-1-2Introductions1.OriginofLTEInMarch2008,theInternationalTelecommunicationsUnion-Radiocommunicationssector(ITU-R)specifiedasetofrequirementsfor4Gstandards,namedtheInternationalMobileTelecommunicationsAdvanced(IMT-Advanced)specification,settingpeakspeedrequirementsfor4Gserviceat100megabitspersecond(Mbit/s)forhighmobilitycommunication(suchasfromtrainsandcars)and1gigabitpersecond(Gbit/s)forlowmobilitycommunication(suchaspedestriansandstationaryusers).,Sincetheabovementionedfirst-releaseversionsofMobileWiMAXandLTEsupportmuchlessthan1Gbit/speakbitrate,theyarenotfullyIMT-Advancedcompliant,butareoftenbranded4Gbyserviceproviders.OnDecember6,2010,ITU-Rrecognizedthatthesetwotechnologies,aswellasotherbeyond-3GtechnologiesthatdonotfulfilltheIMT-Advancedrequirements,couldneverthelessbeconsidered“4G”,providedtheyrepresentforerunnerstoIMT-Advancedcompliantversionsand“asubstantiallevelofimprovementinperformanceandcapabilitieswithrespecttotheinitialthirdgenerationsystemsnowdeployed”.,MobileWiMAXRelease2(alsoknownasWirelessMAN-AdvancedorIEEE802.16m)andLTEAdvanced(LTE-A)areIMT-Advancedcompliantbackwardscompatibleversionsoftheabovetwosystems,standardizedduringthespring2011,andpromisingpeakbitratesintheorderof1Gbit/s.Servicesareexpectedin2013.,Asopposedtoearliergenerations,a4Gsystemdoesnotsupporttraditionalcircuit-switchedtelephonyservice,butall-internetprotocol(IP)basedcommunicationsuchasIPtelephony.Asseenbelow,thespreadspectrumradiotechnologyusedin3Gsystems,isabandonedinall4GcandidatesystemsandreplacedbyOFDMAmulti-carriertransmissionandotherfrequency-domainequalization(FDE)schemes,makingitpossibletotransferveryhighbitratesdespiteextensivemulti-pathradiopropagation(echoes).Thepeakbitrateisfurtherimprovedbysmartantennaarraysformultiple-inputmultiple-output(MIMO)communications.,2LTEAdvancedLTEAdvanced(Long-term-evolutionAdvanced)isacandidateforIMT-Advancedstandard,formallysubmittedbythe3GPPorganizationtoITU-Tinthefall2009,andexpectedtobereleasedin2012.Thetargetof3GPPLTEAdvancedistoreachandsurpasstheITUrequirements.,LTEAdvancedisessentiallyanenhancementtoLTE.ItisnotanewtechnologybutratheranimprovementontheexistingLTEnetwork.ThisupgradepathmakesitmorecosteffectiveforvendorstoofferLTEandthenupgradetoLTEAdvancedwhichissimilartotheupgradefromWCDMAtoHSPA.LTEandLTEAdvancedwillalsomakeuseofadditionalspectrumandmultiplexingtoallowittoachievehigherdataspeeds.CoordinatedMulti-pointTransmissionwillalsoallowmoresystemcapacitytohelphandletheenhanceddataspeeds.Release10ofLTEisexpectedtoachievetheLTEAdvancedspeeds.Release8currentlysupportsupto300Mbit/sdownloadspeedswhichisstillshortoftheIMT-Advancedstandards.,3.DevelopmentofLongTermEvolution(LTE)Thepre-4Gtechnology3GPPLongTermEvolution(LTE)isoftenbranded“4G-LTE”,butthefirstLTEreleasedoesnotfullycomplywiththeIMT-Advancedrequirements.LTEhasatheoreticalnetbitratecapacityofupto100Mbit/sinthedownlinkand50Mbit/sintheuplinkifa20MHzchannelisusedandmoreifmultiple-inputmultiple-output(MIMO),i.e.antennaarrays,areused.ThebelowFigure21-1showsthe4Gwirelessdevices.,Figure21-14Gwirelessdevices,ThephysicalradiointerfacewasatanearlystagenamedHighSpeedOFDMPacketAccess(HSOPA),nownamedEvolvedUMTSTerrestrialRadioAccess(E-UTRA).ThefirstLTEUSBdonglesdonotsupportanyotherradiointerface.,TheworldsfirstpubliclyavailableLTEservicewasopenedinthetwoScandinaviancapitalsStockholm(EricssonandNokiaSiemensNetworkssystems)andOslo(aHuaweisystem)on14December2009,andbranded4G.TheuserterminalsweremanufacturedbySamsung.Currently,thethreepubliclyavailableLTEservicesintheUnitedStatesareprovidedbyMetroPCS,VerizonWireless,andATupto5frequenciespersiteOnesingleplatformtosupportGSM/UMTS/LTEandFDD/TDDsimultaneouslyTheplatform:commonHW&upgradeableSWforconvergence&evolution,Oneutilityset:Co-RRM,Co-TRM,Co-OAM,Co-RNP/RNO,Co-Site/Antenna/FeederThecombinationofradiowirelessequipmentfrequencyThebelowslide(Figure21-2)showsthetransformationandevolutionfromthecurrentGSM/3GnetworktoLTE/4Gnetwork.,Figure21-2Evolutionof2G/3Gto4G,21-2ReadingMaterial21-2-1ReadingComprehensionThePathto4GWillTakeManyTurnsAraceisgoingonrightnowanditsaheatedone.Itsaracetothenextgenerationofuntetheredcommunications4Gmobilebroadbandwireless.Theprizeforreachingthefinishlinefirstorevenfinishingatallcouldbehuge.,Yetthatfinishlinekeepsmoving,asthefourthgeneration(4G)isntyetfullydefined.Infact,spectrumwontbeallocateduntil2007.Standardsprobablywontbecompleteuntiltheyearafterthat.Rightnow,thought,manyteamsacrosstheglobeareinvestingalotoftime,effort,money,andtalenttomakesurethattheyareintherace.,Anyroadracehasthreebasicfundamentals:atrack,acar,andacrew.Theworldwideefforttodevelop4Gsystemanddevicescouldbeconsideredarace.Justasthetrackitselfsetstheboundaryconditionsfortherace,standardssettheboundariesfortelecommunications.,Thefirsttopicofthisarticleisstandardsdevelopmentfor4G,whichrangesfromtheInternationalTelecommunicationsUnion(ITU)tonationalandregionalstandardsdevelopmentorganizations(SDOs).Thepeoplewhoaretollingawaydayinanddayouttomakesuretheirteamwinstherace-the“pitcrew”of4Gresearcharetheengineersworkinginindustrypartnerships,high-techcorporations,anduniversityresearchlabs.Thesecondsectionofthisarticlewillfocusontheirefforts.,Lastly,everyteamneedsavehicletopropelthemtothefinalgoalthefinishline.Intheraceto4G,theracecarsaretheunderlyingtechnologiesthatenablecommunicationstobemoreseamless,useful,andpowerful.,Words&Expressionsuntetheredcommunications无线通信broadbandn.宽带spectrumn.波谱；范围，系列allocatevt.分配，分派investvt&vi.投资，花费fundamentaln.基本原则，基本法则crewn.一队(或一组)工作人员,boundaryn.分界线；界限，范围telecommunication电信InternationalTelecommunicationsUnion国际电信联盟toilaway长时间辛苦的工作corporationn.公司vehiclen.交通工具，车辆；传播媒介，手段propelvt.推进，推动seamlessadj.准确无误的，完全符合逻辑,21-2-2ExercisesI.MultipleChoices.1.Accordingtothepassage,thespectrumwillbeallocatedbytheyearof_.A.2006B.2007C.2008D.2009,2.Accordingtothe2ndParagraph,itisessentialforarealroadracetohave_.A.atrack,acarandabounfaryB.atrack,acarandastandardC.atrack,acrewandabounfaryD.atrack,acrewandacrew,3.Itcanbelearnedfromthepassagethat,the“ITU(Para.3)”referto_.A.InternationalTechnologyUnionB.InternationalTelecommunicationsUnitC.InternationalTelephonesUnionD.InternationalT