TD-SCDMA Principle and Development(大唐李世鹤博士的讲座)

TD-SCDMAPrincipleandDevelopmentDr.ShiheLie-mail:[e-mail]s•Background•PrincipleofTD-SCDMA•Developing•ConclusionHistoryofMobileCommunication•Earlyperiod:fromearly50’s:–Militaryapplication–Withoutsystemconcept–Analogvoiceandsignaling–SingleBSoperation•Conceptofcellularin70’s–Cellularconcept–FrequencyReuse•The1G:Analogsystemin80’s–Differentstandardineachcountry•The2G:Digitalsystemin90’s–GSM/CDMA(IS-95)–Universalstandard•Duplexis1G/2G:FDDCellularConceptMobileNetwork___1stgenerationMobileSWPSTNBSHSorMSOAMMobileNetwork___2ndgenerationMobileSWWithdataPSTNBSHSorMSOAMACUBSCPDNMobileNetwork___3rdgenerationMobileSWCircuitandPacketPSTNNode_BUEOAMACURNCInternetPDNCNandRadioAccess•Network:–Slowprogress,from1Gto3G,circuitswitchtakethesametechnology–Needlongerperiodtostable–Lowrevenueandhighprofit(3%ofmarketinmobile,buthighmargin)•RadioAccess:–Fastchangetechnologies–Keyissueinmobilesystemanduserterminals–Mainpartinequipmentmarket,mobilecommunications•IMT-2000askedproposalforRTT•3mainstreamstandardsare3differentRadioTransmissionTechnologyBasicRequirementforRTT•Q&S–BERrequirementfordifferentserviceindifferentenvironment•Spectrumefficiency–Quantitiesofservicesprovidedinunitbandwidth•Complexity–cost•E&Mcompatibility–Interferencetoothersystem–RejectinterferencefromothersystemsContentsofPhysicallayer–Multipleaccesstechnology–Duplexing–Framestructure–Datamultiplexing–Modulation–Channelcoding/Interleaving–Signaldetection–Antennatechnologies–Randomaccess–Cellsearch–Handover–OtherkeytechnologiesOneGenerationper10years7080900010R/D1G(FDMA)2G(TDMA)3G(CDMA)4G？StandardWidelyapplicationProductDevelopmentWhatisMultiplexmeans•Multipleusersshareasamefrequencyband•Possiblewayformultipleaccess–FrequencyDivisionMultipleAccess(FDMA)•Separatinguserbydifferentcarrierfrequency•Mostpopularwaytobeusedinallmobilesystem–TimeDivisionMultipleAccess(TDMA)•Separatinguserbydifferenttimeslotinsamecarrierfrequency•Commonusedindigitalsystem–CodeDivisionMultipleAccess(CDMA)•Separatinguserbydifferentcodeinsametimeandcarrierfrequency•Wideadoptedin3Gtechnology–SpaceDivisionMultipleAccess(SDMA)•Separatinguserbydifferentlocation(direction)insametime,code,andcarrierfrequency•FuturetechnologybasedonsmartantennaFrequencyPlan•BothFDMAandTDMAneedfrequencyplan__Interferenceinadjacentcarrier•Frequencyre-usefactor•FDMA:samecarriershallbeseparatedbytwocells:re-usefactor=11•TDMA:samecarriershallbeseparatedbyonecells:re-usefactor=7•CDMA:Adjacentcellcanusesamecarrier,re-usefactor=1SpectrumEfficiencyforvoiceservicesin1/2Gsystems•1GFDMA(TACS)–2x25kHzfor1voicech.,frequencyre-usefactor=11–Spectrumefficiency=1/0.05/11=1.8ch/cell/MHz•2GTDMA(GSM)–2x200kHzfor8voicech.,frequencyre-usefactor=7–Spectrumefficiency=8/0.4/7=2.8ch/cell/MHz•2GCDMA(IS-95)–2x1.25MHzfor20voicech.,frequencyre-usefactor=1–Spectrumefficiency=20/2.5/1=8ch/cell/MHz•Theoretically,ifallcodecanbeused,thespectrumefficiencymayreach64/2.5/1=25.8ch/cell/MHz,whichisnearly14timesofFDMAand8timesofTDMA.BasicCDMAconcept•SpectrumSpreadingisatechnologyusedinmilitarycommunicationsince60’s•Basicconcept–Spreadingcode:Walshcode,itisanorthogonalcodewhensynchronized–CDMAisaself-interferencesystem:•Multiplexinterference:betweencodechannels•Multi-pathandDoppler•Interferencefromothersystemandusersinadjacentcell–Near-fareffect–CapacityofaCDMAsystemislimitedbytotalinterferencelevelBasicCDMAIS-95concept•IS-95isaFDDCDMAsystem–OperatedinAMPSfrequencyband(takingBWof41AMPScarriers)–Chiprate1.2288Mcps–Carrierseparation1.23MHz–Channelcodeandinterleaving–Spreadingfactor:64•Studyinginlate80’forpublicmobilecommunication,themainlycontributionsbyQualcommareasfollows–Twosetsofcode:shortcode(Walsh)fordistinguishuserinthecellandlongcode(PNcode)fordistinguishcell–Strictup-linkpowercontrol:toovercomenear-fareffect–Receiver:Rakereceivertoovercomemulti-path–Macro-diversityandsoft-handover:toenhancecapacityandhandoverwithoutinterrupt(suitablefordatatransmission)–VariableratevoicecodertoenhancecapacityCapacityinCDMAsystem:Generalsituation•Basicconsumption:–Idealpowercontrol,receivedpowerlevelfromeachactiveUEisthesame:Eb–Userdistribution:uniform•WhenNusersareactive,thentheinterferencefromthesamecellwillbe(N-1)Eb.Thetotalinterferencefromtheadjacentcells(1stand2ndlayers)willbethesameasthatfromthesamecell.•requiredEb/N0≤lg(SF)+Eb/(N0+2*(N-1)Eb)~lg(SF)-lg(2N)N≤(10lg(SF)-Eb/N0)/2•ReduceinterferenceTechnologiesrelatedtocapacity•Macrodiversity–UEgetdown-linkfrom2to3BSs–EachBSmaytransmitlesspower,lessinterferencetoenhancedown-linkcapacityabout2dB•Powercontrol–Powercontrolerror:usually2to3dB–Becauseoffastfadingandmulti-path–Capacityloss:2dBThepossiblewaytoimproveCDMAsystem•Variablecoderate(byQualcominIS-95)–Basedonvoiceperformance,reducecodingrate.–Maydoublecapacity(halfinterference)forCDMA–KeyIPRforQualcom–UselessinDataservice•SmartAntenna(byTD-SCDMA)–Mostefficienttech–CapacityenhancebyNtimes(Nisthenumberofantennaelements)BasicconceptofDuplex•Duplex:communicationbetweenUEandBSsimultaneously•Traditionaltech:dividedbyfrequency:FDD•TimeDivisi