《专业英语》-Lesson 13 The 4th Generation mobile comm教学材料

■工作任务：通过4G体验高速互联网给生活工作带来的改变。■学习目标：掌握4G的基本概念、标准、特点及意义。■

重点难点：TD和FDD两种网络制式的异同。■

推荐学时：6学时1.Whatis4G？

4Gisthefourthgenerationofbroadbandcellularnetworktechnology,succeeding3G.4Gisanewgenerationofmobilecommunicationtechnologythatintegrates3GandWLANtechnology.Itcantransmitdata,images,audioandvideoquicklyandwithhighquality.Comparedtotheservicesprovidedby1G,2G,and3G,4Gcanprovidefasterdataservices.2.4GstandardBasedontheOFDMA(OrthogonalFrequencyDivisionMultipleAccess)technology,theglobalstandardformulatedby3GPP(The3rdGenerationPartnership)iscalledLTE(long-termevolution).Thefirst-releaseLongTermEvolution(LTE)standard(a4Gcandidatesystem)hasbeencommerciallydeployedinOslo,Norway,andStockholm,Swedensince2009.The4GtechnologyincludesTD-LTE(TimeDivisionLongTermEvolution)andFDD-LTE(FrequencyDivisionDuplexingLongTermEvolution).TheessenceofTD-LTEandFDD-LTEisthesame,withasimilarityofupto90%.(1)FDD-LTETheupanddowndataofFDD-LTEaretransmittedatthesametime,liketwolanerunning.Uplinkanddownloadingcanbecarriedoutsimultaneously.(2)TD-LTETheupanddowndataofTD-LTEaretransmittedseparately,likesinglelanerunning.Throughthe"signallight"controlchannelforuploadingordownloading,uploadanddownloadcannotrunatthesametime.Thisarticlerefersto4GusingIMT-Advanced(InternationalMobileTelecommunicationsAdvanced),asdefinedbyITU-R.AnIMT-Advancedcellularsystemmustfulfillthefollowingrequirements:• Bebasedonanall-IPpacketswitchednetwork.• Havepeakdataratesofuptoapproximately100Mbit/sforhighmobilitysuchasmobileaccessanduptoapproximately1Gbit/sforlowmobilitysuchasnomadic/localwirelessaccess.• Beabletodynamicallyshareandusethenetworkresourcestosupportmoresimultaneoususerspercell.• Usescalablechannelbandwidthsof5–20MHz,optionallyupto40MHz.• Havepeaklinkspectralefficiencyof15-bit/s/Hzinthedownlink,and6.75-bit/s/Hzintheuplink(meaningthat1Gbit/sinthedownlinkshouldbepossibleoverlessthan67MHzbandwidth).• Systemspectralefficiencyis,inindoorcases,3-bit/s/Hz/cellfordownlinkand2.25-bit/s/Hz/cellforuplink.• Smoothhandoversacrossheterogeneousnetworks.3.Advantage

EncodingSpeed（theoretical

value/bps）TechnologyTypicalservice1GAnalog2.4KFDMAvoice

communication2GDigital64KTDMA、CDMAvoice

communication,shortmessageservice,video3GDigital2MWCDMA、SCDMAvoice

communication,data

traffic4GDigital100MOFDM、IMT-AdvancedHighdefinitionvideotransmission、Cloudgaming(1)FastcommunicationspeedThetransmissionspeedof4Gcommunicationcanbeachievedby20Mbps,thehighestoreven100Mbps,whichis50timesthespeedof3G.(2)WidenetworkspectrumComparedwiththebandwidthofthecellularnetworkof3Gnetwork,4Gnetworkismuchhigherincommunicationbandwidth.Thespectrumof4Gchannelisupto100MHz,whichisequivalentto20timesthatoftheW-CDMA3Gnetwork.(3)Flexiblecommunication4Gcommunicationhasmanyservices,suchastransmittingvoicedata,two-waydownloadingandtransmittinginformation,imagesandpicturesatanytimeandanywhere,onlinevideochat,cloudgaming,andsoon.(4)HighintelligentperformanceThedesignandoperationof4Gcommunicationterminalequipmentishighlyintelligent.Itcanachieveintelligentcommunicationandworkwithusersatdifferenttime,environmentandothersettingsfactors.(5)Lowcost4Gcommunicationsolvesthecompatibilityproblemof3Gcommunication,anddirectlybuildsontheinfrastructureof3Gcommunicationnetwork,soastoreducethecostofoperatorsandusers.4.Significanceof4G(1)After4Giscommercialized,investmentandconstructionofnetworkinfrastructurewillbeaccelerated,andcompetitionpatternofcommunicationequipmentmanufacturerswillchange.(2)Thepurchaseandsaleofterminalequipmentwillalsohelpdomesticterminalmanufacturerstodeveloptheglobal4Gmarket.(3)After4Gserviceiscarriedout,theperformanceofoperatorswillbeimproved,whichisconducivetothetransformationandinnovationofoperators.(4)Theconstructionof4Gnetworkandthedevelopmentof4Gserviceswillal