UNIT19

3GNetwork

19-1TechnicalPart19-2ReadingMaterial

19-1TechnicalPart

19-1-1Definition

3Gor3rdgenerationmobiletelecommunicationsisagenerationofstandardsformobilephonesandmobiletelecommunicationservicesfulfillingtheInternationalMobileTelecommunications-2000(IMT-2000)specificationsbytheInternationalTelecommunicationUnion.Applicationservicesincludewide-areawirelessvoicetelephone,mobileInternetaccess,videocallsandmobileTV,allinamobileenvironment.19-1-2Introductions

SeveraltelecommunicationscompaniesmarkethaveextendedtowirelessmobileInternetservicesas3G,indicatingthattheadvertisedserviceisprovidedovera3Gwirelessnetwork.Servicesadvertisedas3GarerequiredtomeetIMT-2000technicalstandards,includingstandardsforreliabilityandspeed(datatransferrates).

TomeettheIMT-2000standards,asystemisrequiredtoprovidepeakdataratesofatleast200kbit/s(about0.2Mbit/s).However,manyservicesadvertisedas3Gprovidehigherspeedthantheminimumtechnicalrequirementsfora3Gservice.Recent3Greleases,oftendenoted3.5Gand3.75G,alsoprovidemobilebroadbandaccessofseveralMbit/stosmartphonesandmobilemodemsinlaptopcomputers.

1.?ConceptofUMTS

TheUMTS(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-SCDMA

TD-SCDMAstandard,developedbytheChinaindependently,hasbecomeoneofthethreemainstream3G,andhasanimportantpositioninChinaorevenininternational,TD-SCDMAusesTDD,smartantenna,jointdetection,dynamicchannelallocation,uplinksynchronization,batonhandoverandotherkeytechnologies.AllofthesehaveTF-SCDMAsystemperformancebeengreatlyimproved,thefollowingwilldescribeeachofthekeytechnologyofTD-SCDMA.

IntroductionstoTDD

3Gsystemisdividedintotimedivisionduplex(TDD)andfrequencydivisionduplex(FDD)modes.FDDisusedinWCDMAandCDMA2000,data’sreceivingandtransmissionoccurintwosymmetric,separatedfrequencychannel.TDDisusedinTD-SCDMA,whichmeansthereceivingandtransmissionoccurinthesamefrequency.

Throughperiodicconversiondirection,alternationuplinkanddownlinktransmissioninthesamecarrier,withaguaranteedtimetoseparatethereceivingandtransmissionchannel.TD-SCDMAsystemisdividedintotheCoreNetwork,RadioAccessNetworkandUserEquipmentfromthefunctions.ThedesigncombinewithFDMA,TDMA,CDMAandSDMAasawhole,hashighspectrumefficiencyandlowemissionpower.

Theuplinkanddownlinkcanbeasymmetricisalsoitsadvantage.TD-SCDMAmaintainbackwardcompatibilitywithGSM,whichisthesecondgenerationmobilecommunicationsystemcurwidelyusedinChinaandtheworld,allowingsmoothtransitionfromGSMto3Gsystems.

AdvantageofTDD:

1)Nosymmetricband.ItcanusetheasymmetricbandflexiblywhichFDDcan’tuse.Itcanadjustthenumberofupanddowntimeslotstosupportasymmetricdatasevices.

2)Uplinkanddownlinkhasthesamefrequency,sothepropagationcharacteristicscanbeconsideredthesameundercertainconditions.It’sbeneficialusingsmartantennasandothernewtechnologies.

3)EquipmentcostsaregenerallylowerthantheFDDsystem.

3.?AdvantagesanddisadvantagesofTD-SCDMA

Advantages

1)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.

Disadvantage

1)TD-SCDMAisfallingbehindWCDMAandCDMA2000incommercialprogress,technologicaldevelopmentandindustrialscale.TD-SCDMAhasanarrowbandwidthandcannottakefulladvantageofmultipath,whichreducethesystemefficiency.

2)Abilityinhigh-speedmobileenvironmentisfallingbehindWCDMAandCDMA2000.

3)TD-SCDMAsystemrequiresdistrictkeepsynchronously,whichneedprecisetiming.Sothereisahighrequirementonthetimingsystem.19-1-3ApplicationCaseorExample

1.?Case1:Applicationinstreammediaservice

WCDMAequipmentsupportingstreammediabusiness,whichsupportsthestandardRTP/RTCPprotocol,providesthehighperformanceadaptivebandwidthandtheindustry’swidelyusedMPEG-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.Figure19-4HTTPAcceleratorandP2PDownloadRateRestriction19-2ReadingMaterial

19-2-1ReadingComprehension

Introductionto3G

TheInternationalTelecommunicationsUnion(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&Expressions

InternationalTelecommunicationsUnion國際電信聯(lián)盟

facilityvt.使便利，減輕……的困難

GSM全球移動通信系統(tǒng)，俗稱全球通

EDGE是一種基于GAM/GPRS網絡的數據增強型移動通信技術，通常被稱為“2.75代技術”

UMTS通用移動通信技術

CDMA2000一種3G移動通信標準

DECT先進數字式無線通信系統(tǒng)

WiMAX微波存取全球互通，是一項新型的寬帶無線接入技術

simultaneousadj.同時發(fā)生的，同時存在的

uplink向上傳輸

HSPA+是HSPA(3GPPR6)的向下演進版本，是上下行能力增強的技術

UMB是CDMA2000系列標準的演進升級版本

LTE3GPP長期演進(LTE)項目，被看做準4G標準

infrastructuren.基礎設施，基礎結構

MIMO多輸入多輸出技術

haltvt&vi.使停下來19-2-2Exercises

I.?MultipleChoices.

1.Accordingtothepassage,3Grefersto______.

A.3games

B.3grades

C.3generations

D.3ndgenerations

2.?About3G,whichofthefollowingisNOTTRUE?

A.3GisbetterknownasInternationalMobile

Telecommunicatio