以太网PHY物理层学习资料PMD子层

1、UniversityofNewHampshireInteroperabilityLaboratory100BUniversityofNewHampshireInteroperabilityLaboratory100BUNIVERSITYofNEWHAMPSHIREINTEROPERABILITYLABOR100BASE-TXPhysicalMediumDependentPresentationOverview:LocationintheOSIStackInterfacewiththePhysicalMediumAt(PMA)Interfacewiththemedium(twistedpwseg

2、ment)PMDsublayerfunctionalityUniversityofNewHampshireInteroperabilityLaboratory100EUniversityofNewHampshireInteroperabilityLaboratory100EUNIVERSITYofNEWHAMPSHIREINTEROPERABILITYLABORStackModelMACIRSMediaAccessControlReconciINationSublayerMEDIUMMilMediaIndependentInterfacePhysicalCodingSublayerPhysic

3、alCodingSublayerPhysicalMediaAttachmentPhysicalMediaAttachment(TwistedPair)PhysicalMediumDependent(TwistedPair)PhysicalMediumDependentUniversityofNewHampshireInteroperabilityLaboratory100BUniversityofNewHampshireInteroperabilityLaboratory100BUNIVERSITYofNEWHAMPSHIREINTEROPERABILITYLABORTP-PMDBlockDi

4、agramInterfacewiththePhysiciMediumAttachment(PM/ThePMDconvertsNRZbitstoNRZIbipresentationtothePMATheprocessisreversedforsignalingcfromthePMAThePMDsignaldetectletsthePMAkrsignalbeingreceivedissatisfactoryLink_controlfromauto-negotiationcarthePHYinordertonegotiatealinkarenablethePHYoncecompleteIinterf

5、acewiththeMediurThePMDconvertsMLT-3symbolsintcsignalswhicharethensentoutovertlElectricalsignalsarereceivedbytheFthemediumandconvertedtoMLT-3sUniversityofNewHampshireInteroperabilityLaboratory100BUniversityofNewHampshireInteroperabilityLaboratory100BUniversityofNewHampshireInteroperabilityLaboratory1

6、00EUnderstandingthe100BASE-ReviewTransmitterFunctionsReceiverFunctionsSgnalDetectReview4B5BBlockCodeNonReturntoZero,(NRZcode)NonReturntoZero,Invertonone(NFMultiLevelTransmit,3levels(MLT-3(The4B5BBlockCodeImplementedinthePCSMapsablockof4bits(anibble)toablockocode-group)Noticethereare25code-groupsando

7、nly24Onlyusecode-groupswithasufficienttransitofacilitatetimingrecovery.Noticethatthe4B5Bblockcoderequiresa5rateincreaseControlCodesSeveralcode-groupsarereservedforcontrolThe/I/orcode-group(11111)issentwlnodatatosendThe/J/K/code-grouppair(1100010001)indidleendsanddatabeginsThe/T/R/code-grouppair(0110

8、100111)incdataendsandidlebeginsThereceptionofanycode-groupotherthandataandcontrolcode-groupsisindicativeofNRZCodeLongrunsof05sor15scancauseprobtimingrecoveryNRZICodeLongrunsof15sareactuallygoodforrecoveryLongrunsof0sarestillaproblemforrecoveryMLT-3Code0SameasNRZIwiththeaddedbonusofredubandwidthSumma

9、ryofCodingTechrTransmitFunctionsNRZI-to-NRZconversionScramblerEncoderTransmitterUniversityofNewHampshireInteroperabilityLaboratory100BUniversityofNewHampshireInteroperabilityLaboratory100ENRZItoNRZConversionThePMDreceivesNRZIencodedbits1PMAThePMDthenconvertstheseNRZIerintoNRZencodedbitsItdoesthisbec

10、ause.StreamCipherScramblerThepurposeofthescrambleristowhdataandevenlydistributethespectraTheinputtothescramblerisreferredplaintextstream.Thescrambleradds(modulo-2)theplstreamtothe/refstreamtoproducetciphertextstream.Alinearfeedbackshiftregister(LFSR)generatethekeystream.LineFeedShiftRegisterSeedUniv

11、ersityofNewHampshireInteroperabilityLaboratory100BUniversityofNewHampshireInteroperabilityLaboratory100EUniversityofNewHampshireInteroperabilityLaboratory100BUniversityofNewHampshireInteroperabilityLaboratory100E100BAUniversityofNewHampshireInteroperabilityLaboratoryScramblerBlockDiagramUniversityof

12、NewHampshireInteroperabilityLaboratory100BUniversityofNewHampshireInteroperabilityLaboratory100EUniversityofNewHampshireInteroperabilityLaboratory100EBooleananalysisofstreamciphers(LetpnbethenthbitoftheplaintextstrearLetknbethenthbitofthekeystream.Letcnbethenthbittheciphertextstream.八denotestheexclu

13、sive-oroperation.Vdenotethecomplementoperation.kn=kn-9Akn-11cn=pnAknNoticethatforidle,pn=7,thereforecnScramblersynchronizatiohn=cnAcn-9Acn-11Remember,foridlecn=!kn.hn=!knA!kn-9A!kn-11hn=!knAknThus,foridle,hn=1.Thedescramblerconsidersitselfsynchronized(itiscertainidleisbeingsent.Whenitfirsttransition

14、sfrom!lockedqlocked,/c/7/77/with!c1:11.Oncelocked,ifthedescramblerfailstoseeidleperiod,itwillgoHockedgdbeginanewsearclMLT-3EncodingRedistributesspectralenergytolowerfrequenciesSerialencodingsystemwiththreepossymbols:+1,0,-1EncoderchangesstatewitheachinpuDirecttransitionbetweenthe+1and-arenotallowedU

15、niversityofNewHampshireInteroperabilityLaboratory100BUniversityofNewHampshireInteroperabilityLaboratory100BUniversityofNewHampshireInteroperabilityLaboratory100EActiveOutputInterface(,ComplicatedexpressionfortransmitteConvertsMLT-3symbolstoelectricalsEmploysdifferentialsignaling.ReceiverFunctionsRec

16、eiverDecoderDescramblerNRZ-to-NRZIconversionActiveInputInterface(AlComplicatedexpressionforreceiver.ConvertselectricalsignalstoMLT-3syToperformtheconversionreliably,th(shouldincorporateadaptiveequalizatibaselinewandercompensation.TheperformsneeoftheAllisevaluateofthebiterrorrate.AdaptiveEqualization

17、Cableattenuatesanddistortsthesignal,maldifficultforthereceivertounderstand.AnequalizerisusedtocancelthecabledistcimplementstheinversefunctionofthecableCableattenuationanddistortionisafunctiorlength.Therearepenaltiesforover-orunder-equalisignal.Anequalizermustaccuratelydeterminecabl-ordertoachievethe

18、bestresultsUniversityofNewHampshireInteroperabilityLaboratory100EUniversityofNewHampshireInteroperabilityLaboratory100EijvjvUniversityofNewHampshire_InteroperabilityLaboratory100ECableDistortionIndu-EogJndooUnderandOver-EqualizationExoOTOP一50L50500062poz一-Bnbfopun250I_JL一40-1PQN-Bnb2(D010015020050-2

19、oUniversityofNewHampshireInteroperabilityLaboratory100EUniversityofNewHampshireInteroperabilityLaboratory100EijvjvUniversityofNewHampshire_InteroperabilityLaboratory100ETime(ns)UniversityofNewHampshireInteroperabilityLaboratory100EUniversityofNewHampshireInteroperabilityLaboratory100EijvjvUniversity

20、ofNewHampshire_InteroperabilityLaboratory100EBaselineWanderDatadependentvariationsinthelowfrequeicomponentofasignal.Themagneticsandcabledefinethelowfreqresponseofthechannel(invariablyhighpasAnyinformationthatasignalcarriesatDCsremovedbythecharinel.ThismaymakeitiforthereceivertounderstandPacketsthat,

21、afterencoding,containasignifofDCenergyarecalledkillerpacketsUniversityofNewHampshireInteroperabilityLaboratory100BUniversityofNewHampshireInteroperabilityLaboratory100BijvjvUniversityofNewHampshire_InteroperabilityLaboratory100EMLT-3DecoderObservetheinputforthedurationof(symbol,theunitintervalIfthes

22、ymbolchangesduringtheunitlogic1issentIfthesymboldoesnotchangeduringinterval,alogic0issentStreamCipherDescrambTheplaintextstreammayberecovereciphertextstreambysubtractingthekusedbythesourcescrambler.Modulo-2subtractionisthesameasnaddition(exclusive-OR).Thekeystreamisuniquelydetermine(LFSR.Theonlyrema

23、iningchallengeissynchthedescramblerwiththesourcescranDescramblerSynchronizaThedescramblercanachievesynchrorwith60orfeweridlebits.IftheinputtothesourcescrambleristheoutputisthecomplementofthekThedescramblersimplyneedsatesttdeterminethatidleisbeingsent.LossofSynchronizationThedescramblerwilllosesynchronizaldoesnotsee20consecutiveidlebitsiperiod.Manyimplementationwillalsolosesynchronizationif58consecut