HSPA技术.docx

HSPA技术.docx

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HSPA技术

HSPA（3.5G）

Student

StudentNumber

Course

Semester

DateofSubmission

CONTENTS

Briefintroduction3

Frequencyallocationandchannelbandwidth5

3.Modulation6

4.Datatransmissionrates8

5.Multiuseraccess（Multiplexing）9

6.Errorcorrection10

7.Improvementsfrom3Gstandardthattheywerederivedfrom.12

8.Reference14

INDEXFORFIGURE

Figure1Physicalchannel5

Figure2QPSK7

Figure316QAM7

Figure4DatatransmissionRates9

Figure5HowRAQRworks11

Figure6TwokindsofHARQ12

Briefintroduction

HSPAisanacronymforHighSpeedPacketAccesscontainsatleast3kindsofstandardsinrecentyears,i.e.HSDPA,HSUPAandHSPA+.3.5GisatechnologystandardinHSDPA.Itdenotesthecontinuationandupgradeof3G.High-SpeedDownlinkPacketAccess（HSDPA）isanenhanced3G（thirdgeneration）mobiletelephonyprotocolinthefamilyofHSPA.Itisanimprovementfor3Gprotocolmobiletelephonedatatransmission.Theoretically,HSDPAisabletotransferspeedsupto14.4Mbpsfordownloadsand2Mbpsforuploads.High-SpeedUplinkPacketAccess（HSUPA）isa3Gmobiletelephonyprotocolofrelease6publishedby3GPPintheHSPAfamilywithup-linkspeedingupto5.76Mbit/s.HSPA+isawirelessbroadbandstandarddefinedin3GPPrelease7alsoknownasEvolvedHigh-SpeedPacketAccess.

AlargenumberoffactorscontributetothebirthofHSDPAare:

●Improvethepeakrate

●Minimizethetransitiondelay

●EnhancethecontrolofQOS

●Raisetheavailabilityofspectrumandchannel

●Decreasethecostofthehigh-speedbusinessandappealtothepotentialcustomers

ThethreephasesoftherevolutionoftheHSDPAare:

Phase1:

BasicHSDPA（3GPPR5）--Theoreticallyspeaking,themaxpeakrateisabletoreach14Mbpsforthereasonsillustratedasfollows.

High-speeddownloadssharedchannelandcontrolchannel,adaptivemodulation（QPSK&16QAM）andratematching,publicmediasharedmediumaccesscontrol（MAC-hs）locatedinNodeBandsupportsofthebusinessoftheBestEffortandBackground.

Phase2:

TheenhancementofHSDPA—AerialArrayProcessingTechnology（3GPPR6）,technicallyspeaking,themaxpeakratecouldreach30Mbps.

Firstly,beamformingtechnology,orsmartantenna,isonlyusedintheterminalofsingleantenna.Secondly,MIMO（MultipleInputMultipleOutput）technologyisusedintheterminalwithmorethan1antenna（4atmost）.ThirdlyitsupportsthebusinessofStreaming.

Phase3:

OFDMimprovesthebitrateinthreeaspects.Tobefirst,thephysicallayersupportsahighermodulationrate.Furthermore,MAC-hs/OFDMchangedthedegreequicklytochoosethesub-carrierwavetoassemble.Finally,Mx-MACcanshiftbetweenOFDMAandCDMAchannel.

Frequencyallocationandchannelbandwidth

Therearethreesimilarkindsofthephysicalchannel,HS-PDSCH,HS-SCCHandHS-DPCCHasshowninthefigureinthefollowing.

Figure1Physicalchannel

ThebitrateofthedatachannelofHS-PhysicalDownlinkSharedCHanneldownlinkisbiggerthan10Mbps.Anditcouldreach15HS-PDSCHs.ThespreadingfactoroftheHS-PDSCHisfixedSF=16.HS-SharedControlCHanneldownlink,ontheotherhand,sendsformattingoptions,forexample,modulation,thesizeofTBS,andetc.ItalsosendstheH-ARQinformation（process,newdata,redundancyversion）.AlmosteveryUEcorrespondsto4HS-SCCH.Inthischannel,spreadingfactorisequalto128.HS-DedicatedPhysicalControlChannelfocusesontheuplinkoftheH-ARQ,ChannelQualityInformation（CQI）andtheSFspreadingfactoristwiceoftheHS-SCCH.

3.Modulation

Basedonthechangesofthetime-varyingdecayingchannel,linkadaptationtechnologybringsaboutthereal-timebalanceoflinkbudgetbyadaptingadjustmentoftransmittingpower,symbolrate,modulationorder,codingrate,codingprojectorthecombinationaloftheabovefactors.Thus,thegoaltoincreasethesystemcapacityandimprovethequalityofthecommunicationisaccomplished.

TherearetwokindsofmodulationappliedinHSDPA:

QPSK（QuadraturePhaseShiftKeying）and16QAM（QuadratureAmplitudeModulation）.ThekeyprincipleistheCodeMultiplexingwhichmeansusing15channelsinparallel.Indetail,usercanchooseboththeCodeDivisionMultiplexing（CDM）andtheTimeDivisionMultiplexing.Atthesametime,userscanallocateatmost15channels.

Theoretically,thethroughputcapacityis14.4Mb/swhen16QAMand15channelsapplied,while3.6Mb/swhenQPSKisapplied.AdaptiveModulationandCoding（AMC）adaptstodifferentSIRanditcanofferhighpeakdatarateintheidealwirelessenvironment.Ifwecomparethetwomodulationsmentionedabove,clearly16QAMchannelconditionisbetterthanQPSK.

Twomodulationschemesareshownbelow:

Figure2QPSK

Figure316QAM

FromFigure2,wecanfindsomeinformationlistedasfollows:

-2bitsmodulatedinQPSK

-Peakrate:

（3.84/16）*15*2Mbps=7.2Mbps

-Chiprate:

3.84Mbps

-Spreadingfactor:

16

-MaximumavailableHS-DSCH:

15

FromFigure3,wecandrawsomeconclusionsasfollows:

-4bitsmodulatedin16QAM.

-Peakrate:

（3.84/16）*15*4Mbps=14.4Mbps

-Chiprate:

3.84Mbps

-Spreadingfactor（SF）:

16

-MaximumavailableHS-DSCH:

15

4.Datatransmissionrates

Theaimof3.5Gisenhancingthepropertiesof3Gbyofferinghighspeeddataratesdownlinkwiththemaxspeed14.4Mbps.Byusingnewadaptivemodulationandcoding,andcarryingpartofwirelessinterfacecontrolfunctionfromwirelessInternetcontrolmachinetobasestation,thehigh-efficiencyschedulingandthefasterretransmissionarerealized.Hence,thepropertiesofHSDPAimprovealot.Comparingtotheglobalused3G,thesignificantfeatureisthattheutilizationrateoftheinternetboostssharply,whilethespeedofthemobilewirelessdownloadincreasestoo.Thehighspeeddownloadratebringstocustomersvisualexperience.Takedownloadingdocumentsasanexample,ifthedownloadofthelowresolutionis20kb,thetimeHSPDAneedsislessthan33%ofWCDMA’s.Forthehighresolutionpicture,suchas25KB,HSPDAtakeslessthan66%ofthetimeWCDMAR99does.Besides,HSDPAwillsavemorethan81%ofthetimewhendownloadingthePowerpointdocument（2MB）.Thehigh-speeddatatransmissionrateleadstheboomofthe3G,thatistosay,thespringupoftheMMS,VOD,WAPbrowse,highcapacityE-mail,andgamesandsoon.Theseserviceshavetotallychangedthemobilenetwork.

ThisdiagrambelowshowsthatthedifferencebetweenDataDownloadedatPeakMobileRatesandtheredbarislabeledastheHSDPA.NownowonderwhyHSDPSissoadvanced?

Figure4DatatransmissionRates

5.Multiuseraccess（Multiplexing）

Appliedindynamiccomplicatedwirelessenvironment,FastSchedulingAlgorithmcontributestomultiusertomakethebestuseofwirelessresourceandimprovethethroughputcapacityofthewholesections.Andtwofactorsareconsidered:

throughputcapacityandfairness.Thebasicprincipleofschedulingisconcentratingonchannelconditioninshorttimewhiletakingaccountofboththroughputcapacityandfairnessofalltheusersinlongtime.Usuallythereare3algorithms:

MaxC/I,RPandPF（ProportionalFair）.

PollingmethodbasedonTIMEresultsinthesequentialserviceanyuserhas.Eachusercangetthesameaverageallocatedtimebutdifferentflowduetothedifferentsituationeachuserisin.Pollingmethodbasedonflowmeanswhateverthedifferentenvironmenteveryuserin,servinginordertoguaranteeeveryusertoacquirethesameflow.

PollingmethodbasedonFLOWmeanswhateverthedifferentenvironmenteveryuserin,servinginorderaimstoguaranteeeveryusertoacquirethesameflow.

MaxC/Imethodshowsthatthesystemfollowsthewirelesschanneldecayingcharacteristicsofeveryuser.ReferringtotheorderofC/IwirelesschannelitdecidestogivetheprioritytoeachuserandguaranteesthateachusercangetthemaxC/Iattimes.

6.Errorcorrection

InstandardARQ,redundantbitsareaddedtodatatobetransmittedusingan error-detectingcode suchas cyclicredundancycheck （CRC）. HybridARQ（AutomaticRepeatreQuest）isahybridtechnologycombiningFEC（ForwardErrorCorrection）andtheARQ.ThemixtureofthetwoadjuststheratefortheprocessofHSDPAflexibly.Inotherwords,HARQhasthefunctionofincrementalredundancyandsoftcombiningretransmission.ThisisagraphsimplyshowingthathowtheHARQworks.

Figure5HowRAQRworks

Thefigurebelowshows2typesofHARQ:

ChaseCombiningandIncrementalRedundancyCombining.Inpractice,theformertypemeansnotgivingupthepreviouslydatapacketbutcombinesavingandretransmissionwithoutchangingtheFEC.Thelattertypepointsoutmoreinformation,i.e.,thewronggroupingwillneverbethrownawaybutcombineanddecodewiththeredundancythetransmittingterminalsends.

Thedatablockisfirstcodedwithapunctured

Turbocode,andthenduringeach（re）transmissionthecodedblockisoftenpuncturedfurtherandsent.Duringeach（re）transmission,thepunctuationpatternusedisdifferent,thereforevariouscodedbitsaresentateachtime.TheHSDPAstandardsupportsincrementalredundancyandchasecombining;however,ithasbeenperformedthatincrementalredundancyalmostalwaysshowsbetterthanchasecombining,atthecostofincreasedcomplexity.

Figure6TwokindsofHARQ

7.Improvementsfrom3Gstandardthattheywerederivedfrom.

3G,alsocalled3GSM,meansliterallythatUMTSis3timesbetterthanGSM.Inthebeginningofthe3Gbusinesspromotion,downloadingvideoswasverypopular.Thebandwidthwasunbalanced.Itconcentratedonthedownlinkdatatransmission.ThedevelopmentofHSDPAsolvesthisstrikingproblem.3.5Gor3G+oryoucansayHSDPAistheoretically6