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1、Summaryof4GcommunicationsMobilecommunicationtechnologyhasundergonethreemajorstagesofdevelopment.Thedevelopmentofeachgenerationistheconceptoftechnologicalbreakthroughsandinnovation.Originatedinthe20thcentury,thefirstgenerationof80years,mainlyinsimulationandfrequencydivisionmultipleaccess
2、(FDMA)technology.Thesecondgeneration(2G)originatedintheearly90s,mainlyintimedivisionmultipleaccess(TDMA)andCodeDivisionMultipleAccess(CDMA)technology.Thirdgenerationmobilecommunicationsystem(3G)canprovidewiderbandwidth,notonlytransmitvoice,butalsohigh-speeddatatransmission,providingfast
3、andconvenientwirelessapplications.However,thethirdgenerationmobilecommunicationsystemisstilldifferentstandardsbasedonregionalgroundcommunicationssystems,althoughitstransmissionspeedofupto2Mb/s,butstillcannotmeettherequirementsofmultimediacommunication,therefore,thefourthgenerationmobile
4、communicationsystems(4G)withattendantcameintobeing.First,4Gcommunicationconcept4Gisstilltobeclearlydefinedsofar,itstechnicalparameters,internationalstandards,networkarchitecture,aswellasbusinesscontentnoclearview.Theendof2002Wi-Fiboom,Wi-Fiwasseenas4Gtechnology.Butadvocatesof4Gtechnolog
5、ythat,4GandWi-Fiaredifferent.June2004,themarketresearchfirmForresteranalystforecasts,4G3GmobileserviceswillbecombinedwiththeWiMaxtechnology.4GwillofferaccessspeedsofEthernet(eg10Mb/s),andthroughacellphoneinthe3GandWiMaxtechnologiestogethertoprovideintegratedwirelessLANandWANservices.WiM
6、ax(ora802.16standard)toprovidewirelessbroadbandservices,themostdistant30miles,therateisabout10Mb/s.In2004,Fujitsureleasedthewhitepaper,theWiMAXreferstothe"4G”wirelesstechnology.Inaddition,therearemanyexpertsontheLAS-CDMAisveryoptimisticthattheLAS-CDMAstandsfor4Gstandards.Whatintheend4Gt
7、echnology?Nowgenerallydescribedasfollows:3Gand4GisaWLANinone,andbeabletotransmithighqualityvideoimages,itsimagequalityandhighdefinitiontelevisiontransmissionpar.4Gsystemisableto100Mb/sdownloadrate,fasterthancurrentdial-up2000timesthespeeduploadcanreach20Mb/s,andbeabletomeetalmo
