GSM EDGE空口编码简介

EDGEsystemoverview

1AgendaWhatisEDGE/EGPRS?NewModulationTechnique8PSKmodulationNewCodingSchemesLinkAdaptationIncrementalRedundancyOthernewFeaturesBiggerWindowSizeEPCRR99QoS

2AgendaWhatisEDGE/EGPRS?NewModulationTechnique8PSKmodulationNewCodingSchemesLinkAdaptationIncrementalRedundancyOthernewFeaturesBiggerWindowSizeEPCRR99QoS

3WhatisEDGE/EGPRS?(1/3)EDGEstandsfor EnhancedDataratesfor

GlobalEvolutionEGPRSstandsfor EnhancedGlobalPacket RadioServices.

EGPRSistheevolutionofGPRSwithinthenewEDGEtechnology

ItisthenextgenerationofWirelessPacketDatatransmissionservice,followingGPRS,aspartofwhatiscalled2.5G.EDGEintroductionkeybenefits:Itallowstotransmitwirelessdatawithathroughput3timeshigherthanregularGSM/GPRSIthasaminimalimpactonanexistingGSM/GPRSnetwork4WhatisEDGE/EGPRS?(2/3)NetworkGSMFrameRelayIPGGSNSGSNIPPCUPCUPCUGPRSIPbackboneX25,IPTransmissionLocalisationEGPRSmodification

/GPRS

/EdgeBSCBSCBTSBTSBTSBTSVLRVLRMSCGMSCHLRHLRVoiceMSCPCUPCUPCUBSSNSS5WhatisEDGE/EGPRS?(3/3)ReminderontheGPRSdatatransferplane

ThereisnodifferenceinEGPRS…IP/X25AppliIP/X25L2L1L2L1ExternalServerTE/MTGGSNSGSNBSSL1L2IPUPD/TCPSNDCPGTPLLCIP/X25AppliSNDCPLLCBSSGPNetworkLayerL1bisL1L2GTPIPUDP/TCPRLCMACPLBSSGPNetworkLayerL1bisRLCMACPL6AgendaWhatisEDGE/EGPRS?NewModulationTechnique8PSKmodulationNewCodingSchemesLinkAdaptationIncrementalRedundancyOthernewFeaturesBiggerWindowSizeEPCRR99QoS

7GSM/GPRStechnologyusesGMSKmodulation(GaussianMinimumShiftKeying).1bitpersymbolNewModulationTechnique(1/2)InEDGE,themodulationusediscalled8-PSK(EightPhaseShiftKeying).3bitspersymbolPhysicalLayermodificationIQ(0,1,0)(0,1,1)(1,1,1)(1,1,0)(1,0,0)(1,0,1)(0,0,1)(0,0,0)IQ108NewModulationTechnique(2/2)ToallowGSM/Edgecompatibility:Samesymbolrateof270ksym/sSameinterferencecharacteristicsSame

burststructure:slot:577μs58symbols(174bits)58symbols(174bits)26symbols3symbols3symbols8.25symbolsTrainingSequenceStealingbitsAteachburstreceptionBlinddemodulation(GMSK/8PSK)ontrainingsequenceStealingbitsreading(indicatesGPRSorEGPRS)Headeranddatadecoding.9NewCodingSchemes(1/6)Thankstothisnewmodulationwecanreachhigherdataratesbutonlywithgoodradioconditions.Tooptimizeefficiencyandqualityofthetransferundervaryingradioconditions,EGPRSuses

9ModulationandCodingSchemes(MCS)

withdifferentrobustnessusingGMSKand8PSKmodulation.Undergoodradioconditions,higherdataratesareachievedusing8PSKmodulationInpoorconditionsthemorerobustGMSKisused,deliveringlowerdataratesWhat

isaModulationand

Coding

Scheme?Almost

the

sameconceptasCoding

SchemesinGPRS.10NewCodingSchemes(2/6)ShortreminderontheprinciplesofGPRSradioallocation:RLC/MACtransportsRLCdatablocksonradioblock.

InGPRS,oneRLCdatablockfitsinaradioblock

(lasting20ms,ie4TDMAframes)ACSdefineshowmuchdataisgoingtobesentonaRLC/MACdatablock,andthereforetheratiobetweenuserdataandprotectiondataThehighertheCS,thelessrobustitisunderdegradedradioconditions(lessprotectionbits)11NewCodingSchemes(3/6)RLCdataencodinginEGPRSBCSRLCBlockHCSHeaderConvolutionalCoding(x3)USFNEWRobustPuncturingNEWUSFCodingUSFPuncturing(variabledependingonMCS,

definestherobustness)NEWBCS:BlockCheckSequenceHCS:HeaderCheckSequenceRLCdata1RadioBlock(4bursts):

464bitsinGMSK1392bitsin8PSK12NewCodingSchemes(4/6)AMCSdefinesthemodulationtousefortransmissionandhowmuchdataisgoingtobesentonaradioblock,andthereforetheratiobetweenuserdataandprotectiondata13NewCodingSchemes(5/6)Caution:InMCS7-8-9,twoRLCdatablocksaresentinoneradioblock.Puncturing1RadioBlock(4bursts):1392bitsin8PSKBCSRLCBlock1HCSHeaderConvolutionalCoding(x3)USFRobustPuncturingUSFCodingUSFRLCdataBCSRLCBlock214NewCodingSchemes

(6/6)Availabledataratepertimeslot(atRLC/MAClevel):GMSK8PSKEGPRSGPRS15AgendaWhatisEDGE/EGPRS?NewModulationTechnique8PSKmodulationNewCodingSchemesLinkAdaptationIncrementalRedundancyOthernewFeaturesBiggerWindowSizeEPCRR99QoS

16LinkAdaptation(1/7)WhatisLinkAdaptation?It’sthefacttochoosetherobustnessofthecodeusedtosenddata(theMCS)dependingontheradiolinkquality.WhentheNWisthetransmitter(DownlinkTransfer):TheNWchoosestheMCStouseto(re)transmitRLCdatablocks.ItbasesitsdecisiononmeasurementreportssentbytheMS.WhentheMSisthetransmitter(UplinkTransfer):TheNWaskstheMSto(re)transmittheRLCdatablockswiththeMCScommandedinPacketUplinkAssignmentorPacketUplinkAck/Nack.17LinkAdaptation(2/7)DoesLinkAdaptationexistinGPRS?Yes,asthereare4possibleCodingSchemes.OnlyCS2isusedonmostNW.NoneedtodoLA.CStouseforsendingischosenonlyatfirsttransmission.

Linkadaptationisnotapplicableforretransmission.

=>RiskofTBFruptureincaseofradioconditiondegradation…tC/IPUANcommandCS4PUANcommandCS2BSN5CS4BSN6CS2BSN7CS2PUANcommandCS2BSN5CS4BSN8CS2BSN1CS4BSN2CS4PUAsscommandCS4BSN2CS4BSN4CS4BSN5CS4BSN3CS418LinkAdaptation(3/7)What’snewwithEGPRS?TherearemoredifferentMCS(9insteadof4)andallofthemarereallyusedEnhancedMeasurementReport.LinkAdaptationisalsoapplicableforretransmission

RLCdatablocscanberetransmittedusingamorerobustMCSincaseofnonacknowledgment.

RLCblocswillberesentusingMCSbelongingtothesamefamily.tC/IPUANcommandMCS5BSN5MCS5BSN6MCS5BSN7MCS5PUANcommandMCS5BSN8MCS5BSN9MCS5BSN1MCS7BSN2MCS7PUAsscommandMCS7PUANcommandMCS7BSN2MCS7BSN4MCS7BSN5MCS7BSN3MCS719LinkAdaptation(4/7)37bytes37bytes37bytes37bytes34bytes34bytes34bytes34bytes34+3bytes34+3bytesMCS3MCS6MCS9MCS3paddingMCS6paddingMCS828bytes28bytes28bytes28bytesMCS2MCS5MCS722bytes22bytesMCS1MCS4FamilyAFamilyBFamilyCMCS6FamilyApadding20LinkAdaptation(5/7)28bytes28bytes28bytes28bytesMCS2MCS5MCS7FamilyBMCS5UsingMCS7,inoneradioblock,therearetwoRLCdatablocksof56bytes(oneheader,buttwoBlockSequenceNumber-BSN).

Forretransmission,usingMCS5,each56bytesRLCdatablockcanbeputinoneradioblock.UsingMCS5,inoneradioblock,thereisoneRLCdatablockof56bytes(oneheader,oneBSN).

Forretransmission,usingMCS2,tworadioblocks(allowing28bytestransmissioneach)willbeneededtosendthe56bytesRLCdatablock.(re-segmentationenable)RulestofollowtodeterminewhichMCSshouldbeusedforretransmissionaredefinedinspecifications.28bytes28bytes28bytes28bytes21LinkAdaptation(6/7)Extractfrom3GPPTS04.60V8.16.022LinkAdaptation

(7/7)ImpactofLinkAdaptationondatarate…05101520253035C/I[dB]0102030405060Bitrate[kbps]MCS9MCS3MCS5MCS4MCS6MCS7MCS8MCS2MCS123AgendaWhatisEDGE/EGPRS?NewModulationTechnique8PSKmodulationNewCodingSchemesLinkAdaptationIncrementalRedundancyOthernewFeaturesBiggerWindowSizeEPCRR99QoS

24IncrementalRedundancy(1/7)InEGPRS,anewmechanismhasbeenputinplace,calledIncrementalRedundancy(IR).

ItenableshigherdataratesthroughcombininginformationfromdifferenttransmissionsofthesameRLCdatablock.IRisbasedonthefactthattheconvolutionalcodeaddsredundancytothedatatobeabletodecodetheblockevenifsomebitsarecorrupted.25IncrementalRedundancy(2/7)Inaradioblockaresent:aheaderandapayload(oneortwoRLCblocks).Itcanhappenthattheheaderiscorrectlydecoded(itscodingismorerobust)andtheRLCblocks(onlyoneorboth)arebadlydecoded.Inthatcase,thecorrupteddatablockcanbestoredwithitsBlockSequenceNumber(BSN).Theblockcanberecombinedwithadifferentiterationofthisblock.26IncrementalRedundancy(3/7)Todefinethedatatobesent,afterconvolutionnalcodethedataarepunctureddependingontheMCS.ForeachMCSthereare2or3differentpossiblepuncturingscheme:P1,P2andP3.ExampleonnextslideWitheitherP1,P2orP3,thereceiverisabletodecodethedata,evenifthereareafewwrongbits(thankstoconvolutionnalcode).Exampleonnextslide27Datatobesent:P1P2P3IncrementalRedundancy(4/7)ExamplewithMCS3:ontransmittersideDatatoencodeDataafterconvolutionnalcode(x3)PuncturingScheme1PuncturingScheme2PuncturingScheme317161514131211109876543210161297652…1714106310…FEDCBA…17161514131211109876543210…17161514131211109876543210…161513121198754217161514131211109876543210…1715141311108431017161410976532128ExamplewithMCS3:onreceiversideReceivedDataNowrongbits P1Afewwrongbits P1Morewrongbits P1 P2P1+P2DecodedDataIncrementalRedundancy(5/7)1714106310…FEDCBA…1714106310…FEDCBA…1714106310…161297652…FEDCBA…1714106310…16129752That’sincrementalRedundancy!29IncrementalRedundancy(6/7)SummaryThesenderhastocyclethroughpuncturingschemes.Theheadercanbedecodedandthedatacorrupted.Combiningtwopuncturingschemes,theprotectionisgreater.Theradiolinkisoptimized.30IncrementalRedundancy

(7/7)ImpactofIncrementalRedundancyondatarate…05101520253035C/I[dB]0102030405060Bitrate[kbps]MCS9MCS3MCS5MCS4MCS6MCS7MCS8MCS2MCS1IR31AgendaWhatisEDGE/EGPRS?NewModulationTechnique8PSKmodulationNewCodingSchemesLinkAdaptationIncrementalRedundancyOthernewFeaturesBiggerWindowSizeEPCRR99QoS

32BiggerWindowSize(1/2)TheRLCWindowisthetablewhereismemorizedwhichRLCblocks(BSN)werecorrectlydecodedorbadlydecoded(onreceiverside)…

ThisinformationissenttothetransmitterinPacketDownlink/UplinkAck-Nack(Bitmap)TheWindowsizeisincreasedfrom64BSNinGPRSto512inEGPRS(in4RX).

TheRLCwindowsizeMaxdependsonthenumberoftimeslotandisallocatedduringtheTBFestablishment.33BiggerWindowSize(2/2)NewAcknowledgementmechanismhasbeencreatedtobeabletoacknowledgeupto512blocksforEGPRS4RX.UseofanAFXalgorithmtocompressedbitmapifnecessaryUseofextendedpollingbitallowingpartialBitmapAcknowledgment34UseofEPCR(1/1)NewmessageusedforUplinkTBFestablishment.WithChannelRequest:AstheMSisnotidentifiedwhenuplinkTBFisestablished,singlephaseaccessdoesnotallowEGPRStransfer.TwoaccessisnecessarytoallowEGPRStransfer(compulsoryforuserdataTBFestablishment).WithEPCR(EGPRSPacketChannelRequest):TheMScanusesinglephaseaccesstoestablishanEGPRSuplinkTBF,asitsEdgecapabilityisimplicitlyincludedinthismessage.Thismessagedefines3accesstypes:Shortaccess,Onephaseaccess(inwhichitcontainsMSmultislotclass)andtwophaseaccess.35Release99QoS

(1/3)MostEdgecapablenetworksareRelease99compliant.ThisincludesnewQualityofServicehandling.QoSisnegotiatedduringPDPcontextactivation.Inrelease97therewere5parameters:ReliabilityclassDelayclassPrecedenceclassPeakthroughputclassMeanthroughputclassInrelease99thereare12:TrafficclassTraffichandlingprioritySDUerrorratioResidualbiterrorratioDeliveryoferroneousSDUsMaximumbitrate[kbps](x2)DeliveryorderMaximumSDUsizeTransferDelayGuaranteedbitrate(x2)36The24.008specification(section)describeshowtheQoSIEisencoded.ConversionrulesbetweenRelease97andRelease99QoSarespecifiedin3GPP23.107-QoSConceptandArchitecture(Section9.1.2)R97attributesR99attributesRelease99QoS

(2/3)37Whendealingwiththenetwork,theMShastotakeintoaccountthereleasesupportedbytheNW:TheMSCversionisgivenbytheMSCRfield,presentinSystemInformationType3MSCR:0->MSCisRelease'98orolderMSCR:1->MSCisRelease'99onwardsTheSGSNversionisgivenbythe