Historicalsummary
Inhistory,theEuropeanTelecommunicationsStandardsInstitute(ETSI)begantostudy3GstandardsafterGSM,andthereareseveralalternatives.Itisbasedondirectserialspreadspectrumcodedivisionmultipleaccess,andthethird-generationresearchinJapanalsouseswidebandcodedivisionmultipleaccesstechnology.Afterwards,thetwoareledtomergeanddevelopedintothethirdgenerationinthe3GPPorganization.ThemobilecommunicationsystemUMTSwassubmittedtotheInternationalTelecommunicationUnion(ITU-T).
TheInternationalTelecommunicationUnionfinallyacceptedW-CDMAaspartoftheIMT-20003Gstandard.
IntroductiontoWCDMA
WCDMAmainlyoriginatedfromearlythird-generationwirelessresearchactivitiesinEuropeandJapan.ThegreatsuccessofGSMhasasignificantimpactonthestandardizationofthird-generationsystemsinEurope.EuropelaunchedtheRACEI(ResearchonAdvancedEuropeanCommunicationsTechnology)programin1988andcontinueduntilJune1992.Itrepresentedthebeginningofthethirdgenerationofwirelessresearchactivities.Between1992and1995,EuropestartedtheRACEIIprogram.ACTS(AdvancedCommunicationTechnologyandService)wasestablishedattheendof1995andproposedtheFRAMES(FutureWirelessBroadbandMultipleAccessSystem)solutionforUMTS(UniversalMobileTelecommunicationSystem).Intheseearlystudies,variousaccesstechnologiesincludingTDMA,CDMA,OFDM,etc.wereexperimentedandevaluated.LaidatechnicalfoundationforWCDMA.
Asanemergingtechnology,WCDMAisalsoderivedfromthepracticeandapplicationofCDMAtechnology.WCDMAisrapidlytakingtheworldbystormandhasoccupied80%ofthewirelessmarket.Asof2013,thereweremorethan3.6billionWCDMAusersworldwide,and156operatorsin170countrieshavecommercialized3GWCDMAservices.
WidebandCodeDivisionMultipleAccess, nimittäin WCDMA.
Abstract:ThisarticlemainlyanalyzesthemaintechnicalcharacteristicsofWCDMA,thedevelopmentstatusandthedirectionoffuturenetworkevolution.ThespecificcharacteristicsandmutualevolutionmethodsofWCDMAtechnologyatdifferentstagesareintroducedrespectively,andthemarketandmainbusinessdirectionsthatWCDMAwillfaceinthefutureareintroduced.ThekeytechnologiesinvolvedintherealizationofWCDMAincluderadiofrequency,intermediatefrequency,basebandRAKEprocessingtechnologyandTurboencodinganddecodingtechnology.Thedifficultiesofdifferenttechnologiesarediscussed.Finally,theprinciplesofenhancedtechnologymulti-userdetectionandsmartantennatechnologyareintroduced.
Avainsanat:MobileCommunication,WCDMA,RadioAccessNetwork,The Third Generation Partnership Project
Abstract:Thepaperpresentsthemaintechnologies,currentsituationandevolutionofWCDMA.ThekeyfeaturesandevolutionprocessduringseveralphasesofWCDMAarealsodiscussed.ThefutureservicesandmarketsthatwillbeoccupiedbytheWCDMAsystemareinvolved.Atlastthekeyimplementationissues,handicapsandenhancedtechnologiesinWCDMAreceiverarealsointroduced.
thirdThenextgenerationmobilecommunicationsystem(alsoknownas3G)isthemobilecommunicationmarketthathasexperiencedtheintroductionofthefirstgenerationofanalogtechnologymobilecommunicationservices,andwasintroducedintotheagendaintheboomingdevelopmentofthesecondgenerationofdigitalmobilecommunicationmarket.Intoday'sInternetdatabusinessisconstantlyheatingup,inthecontextofthecontinuousimprovementoffixedaccessrates(HDSL,ADSL,VDSL),thethird-generationmobilecommunicationsystemhasalsoseenthedawnofthemarket,andithasbecomeatelecomoperatorandcommunicationequipmentmanufacturer.Andcommonusersareconcerned.
Mobilecommunicationtechnologybegantodevelopinitsownway.Variouscountriesandtechnicalorganizationsareconstantlydevelopingtheirowntechnologies.TheUnitedStateshasAMPS,D-AMPS,IS-136,IS-95,andJapanhasPHSandPDC.,EuropeisGSM.Thispattern,ontheonehand,mettheneedsofusersintheearlystagesofmobilecommunicationsdevelopmentandopenedupthemobilecommunicationsmarket.Ontheotherhand,italsocausedartificialisolationbetweenregions,triggeringtheneedforaunifiedglobalmobilecommunicationssystem.ItisagainstthisbackgroundthatITUlaunchedthethird-generationmobilecommunicationsystemspecificationworkin1985.
Duringtheconceptevaluationprocessofthethird-generationmobilecommunicationspecificationproposal,widebandcodedivisionmultipleaccess(WCDMA)technologyhasbecomeoneofthemainstream3Gtechnologieswithitsowntechnicaladvantages.HeremainlyintroducestheoriginofWCDMA,themobilecommunicationmarketandbusinessconditionsitfaces,thecharacteristicsofWCDMAtechnology,thecurrentdevelopmentsituationandthedirectionofevolution.
Tekniset ominaisuudet
Vain jotkin avainominaisuudet on lueteltu
Langaton viestintä vie 5 MHz:n kaistanleveyden
Bittinopeus on 3,84 MCirua
Tuetut multipleksointitilat: FDD,TDD
Nopea lähetysmultimediapalveluiden tukemiseen
Sisäympäristö vähintään 2 Mbit/s
Ulkonakävelyympäristö vähintään 384Kbit/s
Ulkoajoneuvoympäristö on vähintään 144 Kbit/s
Misunderstanding
ThenameofW-CDMAisverysimilartoCDMA,andtherelationshipbetweenW-CDMAandCDMAisalsoverysubtle..Botharebasedoncodedivisionmultipleaccesstechnology,andbothusepartofthepatentedtechnologyofQualcomm.ItisgenerallybelievedthattheproposalofW-CDMAwasdevelopedbysomemanufacturersinordertoavoidpatenttraps,andtheirsolutionshaveavoidedQualcommpatentsasmuchaspossible.
Inthefieldofmobilephones,thetermCDMAreferstoseveralrelatedtechnologiesbelongingtothesecondgenerationofmobilephones,includingcodedivisionmultipleaccessspreadspectrummultiplexingtechnology,andQualcommdevelopedincludingcdmaOne(IS-95)andCDMA2000(IS-2000)CDMAstandardfamily.
TheCDMAmultiplexingtechnologyhasexistedforalongtimebeforeQualcommuseditfortheIS-95protocol.However,becausetheCDMAmultiplexingmethodisthemainfeatureoftheIS-95protocolthatdistinguishesitfromotherprotocolssuchasGSM(usingTDMA)atthattime,theprotocolisnowusuallycalledCDMA.
W-CDMAbelongstothethird-generationmobilephonetechnology.ItalsousesCDMAmultiplexingtechnologyanditissimilartotheQualcommstandard.ButW-CDMAisnotjustamultiplexingstandard.Itisacompletespecificationsetthatdefinesindetailhowthemobilephonecommunicateswiththebasestation,howthesignalismodulated,andhowthedataframeisconstructed.
ThetermCDMAinthefieldofmobilecommunicationsusuallyrefersspecificallytotheCDMAstandardfamilydevelopedbyQualcomm.Theydefineasetofmobilecommunicationprotocols.
CDMA-multipleksointitekniikkaa ei käytetä vain W-CDMAairinterface-protokollalle, mutta myös Qualcommin CDMA-protokollalle.
W-CDMA viittaa erityisesti IMT-2000:ssa määritettyyn matkapuhelinprotokollaan.
W-CDMA-protokollalla ei ole mitään tekemistä Qualcommin kehittämän CDMA:n kanssa.
CDMA-standardiperhe(cdmaOnejaCDMA2000)ei ole yhteensopiva W-CDMA-standardiperheen kanssa.
Teknologia
W-CDMA voi käyttää parittomia tai parillisia taajuuskaistoja, vaikka kaikki nykyiset W-CDMA-laitteet (kuten FOMA ja UMTS) käyttävät kahta 5 MHz:n taajuuskaistaa, toista nousevaa linkkiä ja yhtä ylöslinkkiä varten.
Kehitystila
Mobiiliviestintämarkkinat ja WCDMA
Firstofall,theglobalmobilecommunicationisdevelopingveryrapidly.In1999,itexceeded400millionusers,morethanhalfofwhichItisaGSMuser,andtheothersaremainlyPDCandIS-95users.Accordingtothelatestestimates,theglobalmilestoneofreaching1billionuserswillbeinthefirsthalfof2002.ThetimewhenthenumberofInternet-connectedmobilephonesworldwideexceedsthenumberofInternet-connectedPCswillbeadvancedto2002.In2000,themobilephonemarketwithInternetaccessreached60million.Amongthem,mobilephonessupportingWAP(WirelessApplicationProtocol)accountforabout40million.China'smobilecommunicationusershaveexceeded90million.NokiapredictsthatthenumberofInternetmobilephoneswillincreasetoabout200million,including180millionWAPphones.
MobileoperationsmainlyfacetheintroductionofInternetservicesandothervalue-addedservices,suchasbankingservicesandpositioningservices.Inthisregard,Japan’sNTTDoCoMotooktheleadinintroducingtheI-ModemobileInternetserviceandachievedgreatcommercialsuccess.Atpresent,morethan10,000commercialwebsitesareoperatingtheI-Modeservice.Theintroductionofnewservicesputsforwardnewrequirementsonwirelesscommunicationnetworks.GPRS,adatatransmissionschemebasedontheoriginalstandard,isfarfrombeingabletomeetthedemand,andanewbroadbandmobilecommunicationsystemsuitableforbroadbanddataservicesandIPservicesisneeded.
Secondly,theoriginalserviceuseslessspectrum(lessthan100MHz),andthespectrumefficiencyofthesecond-generationtechnologyitselfisrelativelylow,anditcannotevenmeettheneedsofexistingvoice-basedservices..Infact,thereisaseriousshortageofcapacityinthecentralareasofsomecountriesandcities.TheproblemsinJapanandothercountriesandsomecentralcitiesareparticularlyprominent.
ITU:n suunnitellut 120 MHz (1920 MHz - 1 980 MHz, 2 110 MHz - 2 170 MHz) symmetriset spektriresurssit FDD:lle aikaisintaanWRC92-kokouksessa IMT-2000:lle ja 35 MHz:lle (1900 MHz - 1980 MHz - 1900 MHz - 1920 MHz) ymmetriaspektriresursseja käyttää TDD.800 MHz:n taajuuskaista (806–960 MHz), 1,7 GHz:n taajuusalue (1710–1885 MHz) ja 2,5 GHz:n taajuusalue (2500-2690MHz)lisättiinWRC2000-kokoukseen IMT-2000-palveluita varten.Lisäys kahdesta tulevaisuuden 3G-spektri500MHz Ylhäällä on valtava resurssitilavarattu tulevia sovelluksia varten.
Furthermore,theprocessofglobalintegrationurgentlyneedsagloballyunifiedmobilecommunicationsystem.Theexistingmulti-standardairinterfaceandnetworkequipmentofthesecond-generationmobilecommunicationsystemcannotmeetthisrequirement.Therefore,HighhopesareplacedonthenewWCDMA-FDDmobilecommunicationsystem,whichisexpectedtoachieveglobalharmonization.
Finally,mobilecommunicationtechnologyischangingwitheachpassingday.Thestandardizationandindustrializationofthesecond-generationcommunicationsystemhasbeencompletedforalongtime,anditsmainpurposewasonlytosolvetheneedsofvoicecommunicationatthattime.WiththeincreasingmaturityofwirelesscommunicationtechnologiessuchasCDMAandthedevelopmentofwirelessdatacommunicationtechnologies,theoriginalwirelesscommunicationtechnologysystemneedstobeupdatedaccordinglytoimprovetheutilizationefficiencyofspectrumresourcesandincreasethecostandbenefitofoperators.
3Gstandardizationrequirementsaredrivenbybothmarketandtechnology.3Gstandardformulationandsystemdevelopmenthavebeenbasicallycompleted.Thecommercializationof3Gisalsoinprogress.Theearliestcdma2000-1xinSouthKoreastartedcommercializationattheendof2000,andthecommercializationofWCDMA-FDDinJapanisexpectedtobeginaroundJuly2001.ThecommercializationofWCDMAinChinaandEuropeisplannedtobearound2002.
Vuonna 2001 Japan'sNTTDoCoMo'sFOMA oli maailman ensimmäinen kaupallisesti toimiva W-CDMA-palvelu. J-PhoneJapanPhone(nytSoftwareBank) on julkaissutW-CDMA-pohjaisen palvelun väittäen, että"Vodafone"on 2-yhteensopiva UM:n kanssa. 4).Alkuvuodesta 2003 Hutchison, joka otettiin vähitellen käyttöön UMTS-verkkoaan (viitataan 3:ksi) maailmanlaajuisesti.
MostEuropeanGSMoperatorsplantolaunchUMTSservicessometimeinthefuture,althoughseveralhaveputthisserviceontheirschedules,andsomehaveevenstartedoperatingUMTSnetworkssincetheendof2003.VodafonewasputintooperationinmultipleUMTSnetworksinEuropeinFebruary2004.VodafonealsoplanstobuildUMTSnetworksinothercountries(includingAustraliaandNewZealand).AT&TWireless(nowacquiredbyCingularandundertheAT&Tbrand)hasopenedUMTSinsomecities.Althoughtheprogressofthenetworkconstructionhasbeendelayedduetothecompany'smerger,CingularhasannouncedplanstodeployW-CDMAwithHSDPAin2005.
TeliaSonerabegantoprovide384kbpsW-CDMAserviceinFinlandonOctober13,2004.Servicesareonlyavailableinmajorcities.ThecommunicationrateisapproximatelyUS$2permegabyte.
Taiwanin 3G-palvelu alkoi vuoden 2005 neljännellä neljänneksellä. Aasian ja Tyynenmeren Telecomin lisäksi CDMA2000-, ChunghwaTelecom-, Taiwan'sBigBrother-, FarEastTelecom- jaVerbatimTelecomalluseW-CDMA-järjestelmät.
Kiina Unicomal halusi tarjota W-CDMA-palveluita Manner-Kiinassa 17. toukokuuta 2009 ja alkoi tarjota HSPA-palveluita (ja HSPA+-palveluita joillakin alueilla).
Marketsituation
3Gmarketdevelopmentrequiresbusinesstraction.Unlikethesecond-generationsystem,itismainlytosolvetheneedsofpeople'svoicecommunicationanytimeandanywhere.3Gcansupportdifferentmediaservices.Capabilities,howtodevelopthesecapabilitiesisanimportantsubjectof3Gbusinessdevelopment.
Inordertoprovidetheabilitytotractionintheearlystageofthemarket,theWCDMAspecificationfocusesonthedevelopmentofbusinesscapabilities.WCDMAisexpectedtoprovideveryrichservices.Youcanenjoyordinary,broadbandvoice,multimediaservices,videophonesandvideoconferencephonesthroughWCDMAterminals;Internetapplicationsonmobilenetworksarealsomorecommon,suchasE-MAIL,WWWbrowsing,e-commerce,electronicgreetingcardsandotherservicesandmobilenetworksCombine.Mobileofficeservicesarealsoadevelopmentdirection:Intranetaccess,enterpriseVPN,etc.willbevigorouslypopularized.Informationandeducationserviceswillhavegoodapplicationprospects,andmobileapplicationssuchasstockinformation,trafficinformation,weatherinformation,locationservices(LCS),onlineclassrooms,andonlinegameswillgreatlyenrichpeople'slives.
IMT-2000proposesnewcharacteristicservicessuchasSoLSAandVHE,makingserviceprovisionmoreflexibleandpersonalized.InR'99,existingtechnologiessuchasMExE,SAT,andCAMELcanbeusedtoembodytheVHEbusinessplatformconcept.WCDMAsupportsmultiplecalls,thatis,itcanprovidetheterminalwiththeabilitytoconductmultipleCScallsorPSsessionsatthesametime.WCDMAprovidesabundanthandovercapabilities(samefrequency,differentfrequencyandhandoverbetweendifferentsystems)toensurebusinesscontinuityissuesinmobilenetworks.
BusinessIP,packetization,multimedia,personalization,andsimplificationofgenerationarethegeneraldevelopmenttrends.Inthefutureservicegenerationsystem,mobilenetworkoperators,serviceproviders(ISP)andcontentproviders(ICP)willworkcloselytogether.Itisparticularlyimportantthatthefuturenetworkwillprovideanopenservicestructure(OSA),andmobileoperatorscandevelopavarietyofflexibleservicesontheopenserviceplatformprovidedbythenetworkbythemselvesorincooperationwithotherorganizations,soastosatisfymobileusers.Higherrequirements.
Vertailu muihin standardeihin
Aluksi CDMA2000:n suunniteltiin käyttävän useita 1,25 MHz:n kantoaaltoja, mutta se hylättiin, kun taas W-CDMA käyttää yhtä 5 MHz:n kaistanleveyden kantoaaltoa.
ITUIMT-2000-standardissa W-CDMA:ta pidetään CDMA-suorana sarjahajaspektrina, ja CDMA2000:tä kutsutaan "multi-carrierCDMA:ksi".
W-CDMA-standardiperhe (kuten FOMA, UMTS) ei ole yhdenmukainen CDMA-standardiperheen kanssa (kutencdmaOne ja CDMA2000).
Evoluutio
Jatkokehitys
Jotta ei voida täyttää kaupallistamisen ja teknologisen kehittämisen tarpeet ja varmistaa verkko-operaattoreiden investoinnit, 3GPP on jakanut WCDMA-standardin kahdeksi suureksi.
Release99(R99)version:SinceDecember1999,itwillbeupdatedeverythreemonths.TheJune2000versionisbasicallystableandreadyfordevelopment.TheversionsinSeptember,DecemberandMarch2001aremorecomplete;themaininterfacesofthewirelessaccessnetworkIu,Iub,andIuralladoptATMandIPmethods.ThenetworkisanATM-basednetwork;thecorenetworkisbasedontheevolvedGSMMSCandGPRSGSN;Thecircuitislogicallyseparatedfromthepacketswitchingnode.
Versio 2000(R00)(on muutettu Release4,5...):Esittelee pääasiassa"all-IPnetwork",alun perin ehdotettu IP-pohjainen ydinverkkorakenne,ei aloittanut merkittävää standardointityötä,todellinen"all-IP"standardin odotetaan valmistuvan Samaan aikaan IP laajenee vähitellen ydinverkosta (CN) radioliityntäverkkoon (RAN) andterminal (UE).
ThemainstandardoftheR99versionhasbeencompletedandpublishedin2000.Itcanprovideallthefoundationsfortherealizationofnetworksandterminals,includingallthefunctionalfoundationsoftheuniversalmobilecommunicationnetwork,andprovidethenecessaryguaranteesforthecommercialversion.ThefutureRelease4andRelease5willaddnewfunctionsonthebasisofthesefunctionstoensurethecontinuityofthestandard.FromtheframeworkoftheentireR99network,itcanbeseenthattheinitialWCDMAnetworkcancoexistwiththeGSMnetwork.GSMachievesfullcoverageofawidearea,whileWCDMAachievescoverageofpartofthebusiness-intensiveandhigh-qualitybusinessarea.Thisismainlytoensuretheinvestmentandsmoothtransitionofthesecond-generationoperators.
TheexistingRelease99versionofWCDMAsystemperformanceandservicesaremainly:
Release99versionofWCDMAprovidesanewwirelessaccessnetwork-UTRAN,whichimprovesthespectrumutilizationrate.Highdatatransmissioncapacity,thedatarateis384kbit/sinwidearea,2Mbit/swhenmovingslowlyinasmallrange,supportsAMRvoicecodectechnology,canimprovevoicequalityandsystemcapacity,Iub,IurandIuinterfacesarebasedonATMTechnology,providinganopenIubinterface;
TheWCDMAcorenetworkofRelease99versionisdividedintoCSdomainandPSdomain,whicharebasedontheevolvedMSC/GMSCandSGSN/GGSNrespectively.TheCSdomainismainlyresponsibleforcircuit-typeservicesRelatedfunctionssuchascallcontrolandmobilitymanagement,incallcontrol:useTUP,ISUPandotherstandardISDNsignaling,mobilitymanagementadoptsthefurtherevolvedMAPprotocol,andthephysicalentitysimilartoGSMincludesMSC,GMSC,andVLR.ThePSdomainismainlyresponsibleforfunctionssuchassessioncontrolandmobilitymanagementrelatedtopacket-basedservices.OnthebasisoftheoriginalGPRSsystem,someinterfaceprotocols,workflowsandservicefunctionsarepartiallymodified.Thevoicecodecisimplementedinthecorenetwork.Supportinter-systemhandover(GSM/UMTS),enhancedsecurityperformanceandchargingsystem;
Themainserviceplatformsthatcanbeprovidedinclude:basicpositioningservice,numberportabilityservice,enhancementofintelligentservice,GSMandHandoverbetweenUMTScansupportallGSManditssupplementaryservices,suchascallforwardingwithoutanswer,newUSIMcardprotocol,whichcanimproveuserparticipationandoperation,andsupportbusinessapplicationprogramminginterfaceAPI(openservicestructure),Supportmulticastservices,64kbit/scircuitdatabearerservicesandmultimediaservices;
Järjestelmän kehitys
Edeltävän perusteella voimme tehdä yhteenvedon WCDMA-järjestelmän kehitysmenetelmästä seuraavasti:
-Release99providesathird-generationfull-networksolution.Thestandardhasmatured,andithastheimplementationfoundation,basicfunctionsandexpansionconditionsofcellularmobilenetworks:
–uusi langaton yhteysverkkoUTRAN
p>–YhdistettyCSandPSdomain-ydinverkko
– Enhanced GSMcorenetworkGERAN
-Release4andRelease5furtherincreasenewservices,optimizetechnicalsystemsandThenetworkstructureisthesupplementandimprovementoftheRelease99protocol,whichensuresthecontinuityoftheWCDMAsystem:
– Kaikki IP-verkko
–Uusi langaton pääsymenetelmä-HSDPA
–Parannettu älykäs verkko ja tietoturva
Tekniset ominaisuudet
Tekniset ominaisuudet
1. Tukiaseman synkronointitila: tukiasynkronisen ja synkronisen tukiaseman käyttötilan, joustava verkko
2.Signaalin kaistanleveys: 5 MHz; Chiprate: 3,84 Mcps
3.Transmitdiversity-tila: TSTD(aikakytkinlähetysdiversiteetti),STTD(aika-avaruuskoodauslähetysdiversiteetti),FBTD(FeedbackTransmitDiversity)
4. Kanavakoodaus: Convolutional Code ja Turbocode, Support2Mrateddataservice
5.Modulaatio:Uplink:BPSK;Downlink:QPSK
6. Virranhallinta: uplink-anddownlink suljetun silmukan tehonsäätö, ulkoisen silmukan tehonsäätö
7.Demodulaatiotila: pilottiavusteinen koherenttidemodulointi
8. Puhekoodaus: AMR, yhteensopiva GSM:n kanssa
9.ThecorenetworkisbasedontheevolutionoftheGSM/GPRSnetworkandmaintainscompatibilitywiththeGSM/GPRSnetwork
10.MAPtechnologyAndGPRStunneltechnologyisthecoreofthemobilitymanagementmechanismoftheWCDMAsystem,maintainingcompatibilitywiththeGPRSnetwork
11.SupportSupportsofterandoverandsofterhandover
12.Thebasestationdoesnotneedtobestrictlysynchronized,andthenetworkisconvenient
Advantages
TheadvantageofWCDMA-FDDliesinitshighchiprateEffectiveuseoffrequencyselectivediversityandspatialreceptionandtransmissiondiversity,whichcansolvemultipathandfadingproblems.Turbochannelcodinganddecodingareusedtoprovidehigherdatatransmissionrates.TheFDDformatcanprovidewide-areafullcoverage.Auniquecellsearchmethodisusedforthedifferentiationofdownlinkbasestations,whichdoesnotrequirestrictsynchronizationbetweenbasestations.Usingcontinuouspilottechnology,itcansupporthigh-speedmobileterminals.Comparedwiththesecond-generationmobilecommunicationstandard,WCDMAhas:largersystemcapacity,bettervoicequality,higherspectrumefficiency,fasterdatarate,strongeranti-fadingability,andbetteranti-multipathItcanbeappliedtomobileterminalsupto500km/hintermsoftechnicaladvantages,andcanmakeasmoothtransitionfromtheGSMsystemtoensuretheoperator’sinvestmentandprovideagoodtechnicalfoundationfor3Goperations.
Keytechnology
ThekeytechnologyofWCDMAindustrializationincludesradiofrequencyandbasebandprocessingtechnology,includingradiofrequency,intermediatefrequencydigitalprocessing,RAKEreceiver,channelcodec,powercontrolandotherkeytechnologiesAndmulti-userdetection,smartantennaandotherenhancementtechnologies.
RFandIF
TheRFpartisatraditionalanalogstructure,whichrealizestheconversionofRFandIFsignals.TheRFuplinkchannelpartmainlyincludesautomaticgaincontrol(theRFpartisatraditionalanalogstructure,whichrealizestheconversionofRFandIFsignals.TheRFuplinkchannelpartmainlyincludesautomaticgaincontrol(RFAGC),receivingfilter(Rxfilter)anddownconverterThedownstreamchannelpartofradiofrequencymainlyincludessecondaryup-conversion,broadbandlinearpoweramplifierandradiofrequencytransmissionfilter.Theintermediatefrequencypartmainlyincludesupstreamde-aliasingfilter,down-converter,ADCanddownstreamintermediate-frequencysmoothingfilter,up-converterAndDAC.DifferentfromtheGSMsignalandthefirst-generationsignal,thesignalbandwidthofWCDMAisawidebandsignalupto5MHz.ThelinearityandefficiencyofthewidebandsignalRFpoweramplifierareuniversalcontradictions.
RAKE-vastaanotin
RAKEreceiverisaclassicdiversityreceiverdesignedspecificallyforCDMAsystems.Itstheoreticalbasisis:whenthepropagationdelayexceedsonechipperiod,multipathsignalscanactuallyberegardedasuncorrelated.
ThecorrelatorwithDLLisaphase-lockedloopthatwillsoonerorlater.Itconsistsoftwocorrelators(earlyandlate),andthedemodulationcorrelatorisdifferentfromthedemodulationcorrelatorby±1/2(or1/4)chips.Soonerorlater,thesubtractionofthecorrelationresultofthegatecanbeusedtoadjustthecodephase.Theperformanceofthedelayloopdependsontheloopbandwidth.
ThefunctionofdelayestimationistoobtainthedifferencethroughthematchedfilterSignalenergydistributionatthetimedelayposition,identifythemultipathpositionswithlargerenergy,andallocatetheirtimetothedifferentreceivingpathsoftheRAKEreceiver.Themeasurementaccuracyofthematchedfiltercanreach1/4-1/2chips,andtheintervalbetweendifferentreceivingpathsoftheRAKEreceiverisonechip.Inactualimplementation,iftheupdatespeedofthedelayestimateisveryfast(forexample,onceeverytensofms),thereisnoneedforaphase-lockedloopsoonerorlater./p>
Duetotheinfluenceoffastfadingandnoiseinthechannel,thephaseofeachpathactuallyreceivedvariesgreatlyfromthephaseoftheoriginaltransmittedsignal.Therefore,thephaseshouldberotatedaccordingtotheresultofchannelestimationbeforemerging.ThechannelestimationintheactualCDMAsystemisbasedonthepilotsymbolscarriedinthetransmittedsignal.Accordingtowhetherthetransmittedsignalcarriescontinuouspilots,thephasepredictionbasedoncontinuouspilotsandthephasepredictionbasedondecisionfeedbacktechnologycanbeusedrespectively.Method.
Inthesystem,eachusermustbemultipathsearchedanddemodulated,andthechiprateofWCDMAisveryhigh,andtheprocessingvolumeofitsbasebandhardwareisverylarge.Certainlydifficult.
Kanavakoodaus ja koodauksen purku
Channelcodinganddecodingaremainlytoreducethesignalpropagationpowerandsolvetheinevitablefadingproblemofthesignalinthewirelesspropagationenvironment.Thecodinganddecodingtechnologyiscombinedwiththeinterleavingtechnology.Usecanimprovethebiterrorrateperformance.Comparedwiththecaseofnocoding,thetraditionalconvolutionalcodecanincreasethebiterrorratebytwoordersofmagnitudeto10-3~10-4,whiletheTurbocodecanfurtherincreasethebiterrorrateto10-6.ThecandidatechannelcodinganddecodingtechnologiesforWCDMAoriginallyincludedReed-SolomonandTurbocode,Turbocodeisfinallyadoptedas3GdatacodinganddecodingtechnologybecauseitscodinganddecodingperformancecanapproachtheShannonlimit.Convolutionalcodesaremainlyusedforlowdataratevoiceandsignaling.Turbocodingconsistsoftwoormorebasicencoderscascadedinparallelthroughoneormoreinterleavers:
TheprincipleofTurbocodeisbasedonthealgorithmandstructuremodificationoftraditionalconcatenatedcodes.InnerinterleavingTheintroductionofthefiltermakesthepositivefeedbackofiterativedecodingwelleliminated.Turbo'siterativedecodingalgorithmsincludeSOVA(softoutputViterbialgorithm),MAP(maximumposteriorprobabilityalgorithm),etc.SincetheperformanceimprovementofeachiterationoftheMAPalgorithmisbetterthanthatoftheViterbialgorithm,theiterativedecoderoftheMAPalgorithmcanobtaingreatercodinggain.TheactualimplementationoftheMAPalgorithmistheLog-MAPalgorithm,whichplacestheMAPalgorithminthelogarithmicdomainforcalculation,reducingtheamountofcalculation.
ThedifficultyintherealizationofTurbodecodingalgorithmliesinthedecodingrateandcorrespondingnumberofiterationsforhigh-speeddata.ExistingDSPshavebuilt-inbasicalgorithmsrequiredbydecoders,sothatTurbodecodingcanbedirectlyrealizedbyrelyingonDSPchips.WithoutusingASIC.
Implementationdifficulties
Smartantennatechnologyusesadaptivebeamformingtechnologytoincreasethedirectionalpatterngainoftheuser'sdirectionofarrival,andatthesametimeusethezeropointofthedirectionalpatterntoreducespatialhighpowerUserinterference.Themaindifficultyliesintheinconsistencyandcorrectiontechnologyofmulti-channel,thehighcomplexityofRAKEreceivercombinedwithbasebandprocessing,andtheinconsistencyoftheuplinkanddownlinkdirectionsofarrivalcausedbyFDDtechnology.