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ADSL.ppt

ADSL

wanteng05
2012-03-04 0人阅读 举报 0 0 暂无简介

简介:本文档为《ADSLppt》,可适用于IT/计算机领域

ADSL(asymmetricdigitalsubscriberline)ADSL(asymmetricdigitalsubscriberline)Providedby:IMing,Chen()Advisor:ProfessorAusifMahmoodSpringADSL(asymmetricDigitalSubscriberLine)ADSL(asymmetricDigitalSubscriberLine)Digitalmeansalineabletocarrydatatrafficinitsoriginalform,asopposedtoanalogueSubscriberLine*thelineconnectingtheindividualsubscriber(egahousehold)tothelocalexchangeAnaloguephonelinesusedforvoicephonecallsuntiltodayhavebeenanaloguelinesandwehaveusedMoDems(ModulatorDemodulator)toconvertthedigitaloutputofthecomputertoanalogueformfortransmissionandbackintodigitalformADSL(asymmetricdigitalsubscriberline)ADSL(asymmetricdigitalsubscriberline)unusedfrequenciesoncoppertelephonelinestotransmittraffictypicallyatmultimegabitspeedsallowvoiceandhighspeeddatatobesentsimultaneouslyoverthesamelineserviceis'alwaysavailable'WithADSLyouarewiredforspeedAdvantagesAdvantagesUsuallyprovidethemodemaspartoftheinstallationInternetDoesn’tneednewwiringConnectionopenandstillusethephonelineforvoicecallsRegularmodem(MbpsvsKbps)DisadvantagesDisadvantagesBetterconnectionifclosertotheprovider’sFasterreceivingthansendingdataNotavailableeverywhereADSLishighspeedconnectionthatusesthesamewiresasaregulartelephonelineADSLishighspeedconnectionthatusesthesamewiresasaregulartelephonelineADSLEquipmentADSLEquipmentADSLusestwopiecesofequipment,oneonthecustomerendandoneattheInternetserviceprovider,telephonecompanyorotherproviderofADSLservicesAtthecustomer'slocationthereisanADSLtransceiver,whichmayalsoprovideotherservicesADSLserviceproviderhasanADSLAccessMultiplexer(DSLAM)toreceivecustomerconnectionsHowADSLWorkHowADSLWorkPOTS(Plainoldtelephoneservice)referstostandardtelephoneservicetelephoneservicesbasedonhighspeed,digitalcommunicationslines,suchasISDNandFDDI,arenotPOTSmaindistinctionsbetweenPOTSandnonPOTSservicesarespeedandbandwidthPOTSisgenerallyrestrictedtoaboutKbps(,bitspersecond)POTSnetworkisalsocalledthepublicswitchedtelephonenetwork(PSTN)TheSimpleADSLTransceiverTheSimpleADSLTransceiverADSLfreestheenduserfromthelimitationsofvoicebandwidth,providingbandwidthmeasuredinthehundredsofkHzandenablingcommunicationsatleasttimesfasterthanthatavailableoverpurePOTSallowingyoutomakephonecallsorfaxistransmittingorreceivingLetusexamineatypicalADSLmodemtoseehowitaccomplishesthisATypicalADSLTransceiverBlockDiagramATypicalADSLTransceiverBlockDiagramADSLhardwareequipmentsADSLhardwareequipmentsDSLAM(DigitalSubscriberLineAccessMultiplexer)DSLAccessMultiplexer,amechanismataphonecompany'scentrallocationthatlinksmanycustomerDSLconnectionstoasinglehighspeedATMlineCPE(CustomerPremiseEquipment)communicationsequipmentthatresidesonthecustomer'spremisesForexample,DSLmodemisCustomerPremiseEquipment(CPE)TheroleoftheDSLAMTheroleoftheDSLAMThepathofdataalongtheDSLfromitscommercialorresidentialsource,viathelocalloop,totheCO(CentralOffice)ThelocalloophereterminatesattheMainDistributionFrame(MDF),tobepickedupbyoneoftheCO'smanyDSLmodemsIftheformofDSLallowsforthecarryingofbothanaloganddigitalsignals,aPOTSsplitterwillseparateoutthesignalsTheanalogsignalwillfollowitstimehonoredpathalongthecopperwireinfrastructureForthedigitalsignal,however,onestepbeforethesignalcanbeshotalongtoitsdestinationTherolesoftheADSLmodemTherolesoftheADSLmodembpsthedevicesendingdatatoyourcomputeris,bps,youmustreceiveitat,bpsDatacompressionSomemodemsperformdatacompression,whichenablesthemtosenddataatfasterratesHowever,themodematthereceivingendmustbeabletodecompressthedatausingthesamecompressiontechniqueFlashmemorySomemodemscomewithflashmemoryratherthanconventionalROM,whichmeansthatthecommunicationsprotocolscanbeeasilyupdatedifnecessaryAnADSLNetworkAnADSLNetworkModulationsUsedinADSLModulationsUsedinADSLModulationisthekeyofADSLtechnologyitisaprocessinwhichonesignalmodifiespropertiesofanotherSeveralmodulationtechnologiesareusedbyvariouskindsofADSLModulationsUsedinADSLModulationsUsedinADSLDiscreteMultitoneTechnology(DMT)CarrierlessAmplitudeModulation(CAP)MultipleVirtualLine(MVL)QAM(quadratureamplitudemodulation)QAM(quadratureamplitudemodulation)Amethodofcombiningtwoamplitudemodulated(AM)signalsintoasinglechannel,therebydoublingtheeffectivebandwidthQAMisusedwithpulseamplitudemodulation(PAM)indigitalsystems,especiallyinwirelessapplicationsDiscreteMultitoneTechnology(DMT)DiscreteMultitoneTechnology(DMT)Discretemultitone(DMT)isamethodofseparatingaDigitalSubscriberLine(DSL)signalsothattheusablefrequencyrangeisseparatedintofrequencybands(orchannels)ofkHzeachDMTusesthefastFouriertransform(FFT)algorithmformodulationanddemodulationDividingthefrequencyspectrumintomultiplechannelsallowsDMTtoworkbetterwhenAMradiotransmittersarepresentWithineachchannel,modulationusesquadratudeamplitudemodulation(QAM)Byvaryingthenumberofbitspersymbolwithinachannel,themodemcanberateadaptiveCarrierlessAmplitudeModulation(CAP)CarrierlessAmplitudeModulation(CAP)CarrierlessAmplitudePhaseModulation(CAP)isadesignofAsymmetricDigitalSubscriberLinetransceiverdevelopedbyBellLabsCAPwasthefirstADSLdesigntobecommerciallydeployedand,asofAugust,wasinstalledonmorelinesthananyotherCAPisavariationofQuadratureAmplitudeModulation(QAM),themodulationusedbymostexistingmodemsinWithCAP,thethreechannels(POTS,downstreamdataandupstreamdata)aresupportedbysplittingthefrequencyspectrumVoiceoccupiesthestandardKHzfrequencyband,followedbytheupstreamchannelandthehighspeeddownstreamchannelStandardsandInteroperabilityStandardsandInteroperabilityStandardsandInteroperabilityarethemostimportantofanysuccessfulcommunicationstechnologyTheAmericanNationalStandardsInstitute(ANSI)hasapprovedDMTasthestandardmodulationmethodforAsymmetricDigitalSubscriberLoop(ADSL)inIncontrast,CAPremainsasinglesourceproprietarytechnologythatnothasbeenstandardizedCAPisaproprietarysinglesourcetechnology,sointeroperabilitybetweendifferentchipsetscannotbedemonstratedoranticipatedNoiseImmunity,andImpulsesNoiseImmunity,andImpulsesDMTtransmittercaneasilymonitorthechannelandthenadaptitstransmissiontothecharacteristicsofthephoneline,andcontinuouslyupdates(bitswapping)tomaintaintheoptimumForeveryline,theDMTsystemtransmitsthe"best"possiblesignalACAPsystemcannotmodifyitstransmitterandsoitneedstotrytoundoalltheattenuationandnotchesinonefellswoopatthereceiveratoughchallengeCAPsystemsareoftendescribedinevaluationsasnotbeingasrobustasDMTsystems,ornotastoleranttobridgetapsErrorControlErrorControlDMTuseserrorcorrectionasapotenttechniquetoimproveperformanceandefficiencyatlowcostCAPomitsit,hurtingbothperformanceandinteroperabilityTheexistingCAPchipsetonlysupportserrorcorrectiononthedownstreamandtheupstreamiscompletelyunprotectedtheproposedadhocreportdropseventhat,sothereisnostandarddefinederrorcorrectionPerformancePerformanceDMTisadeptatmatchingitstransmissionchannelstothechannel(byvaryingeachofthetonesindependently),itisbothmoreefficientinitsuseofbandwidththanCAP,anddelivershigherperformanceunderanyrealisticcircumstanceInternetAccessInternetAccessDMTisdesignedfordataaccessitisaInternetaccesssolutionofchoiceCAPwasakindsolutionforvideoondemand,itwasinitiallyunsuitable,requiredadrasticredesignandisstilllesssuitedADSLModulationSummaryADSLModulationSummaryDMTandCAParetwomajormodulationtechnologiesfortheADSL,butDMTisthemostwidelyusedandappearstobebecomingtheindustrystandardDMTisadoptedinternationallybytheAmericanNationalStandardsInstitute(ANSI),EuropeanTelecommunicationsStandardsInstitute(ETSI)andtheInternationalTelecommunicationsUnion(ITU)DMThasbetterperformancethatCAPDMTisbettersolutionthanCAPTransmissionImpairmentsTransmissionImpairmentsEverynetworksuffersfromimpairmentstherearethreetypesoftransmissionimpairmentsAttenuation,DelayDistortionandNoiseAttenuationAttenuationItisthestrengthofsignaloffwithdistanceoveranytransmissionmediumForguidedmedia,thisreductioninstrength,orattenuation,isgenerallylogarithmicandthusistypicallyexpressedasaconstantnumberofdecibelsperunitdistancesForunguidedmedia,AttenuationisamorecomplexfunctionofdistanceandthemakeupoftheatmosphereDelayDistortionDelayDistortionItisaphenomenonpeculiartoguidedtransmissionmediaThedistortioniscausedbythefactthatthevelocityofpropagationofasignalthroughaguidedmediumvarieswithfrequencyDelayDistortionisparticularlycriticalfordigitaldataNoiseNoiseItisthatforanydatatransmissionevent,thereceivedsignalwillconsistofthetransmittedsignal,modifiedbythevariousdistortionsimposedbythetransmissionsystem,plusadditionalunwantedsignalsthatareinsertedsomewherebetweentransmissionandreceptionImpulseNoiseThermalnoiseCrosstalkIntermodulationnoiseThermalnoiseThermalnoiseresultsfromthermalagitationofelectronsinaconductorEvenlydistributedovertheentireradiofrequencyspectrum:whitenoiseItispresentinallelectronicdevicesandtransmissionmediaandisafunctionoftemperatureIntheFMbroadcastbandwherethereisnostation,thehissinthebackgroundisthethermalnoiseThermalnoisecannotbeeliminatedIntermodulationnoiseIntermodulationnoiseresultswhensignalsofdifferentfrequenciessharethesametransmissionmediumItproducessignalsatafrequencythatisthesumordifferenceofthetwooriginalfrequenciesormultiplesofthosefrequenciesImpulsenoiseImpulsenoiseItisnoncontinuousconsistingofirregularpulsesornoisespikesofshortdurationandofrelativelyhighamplitudeItisgeneratedfromlightningandfaultsandflawsinthecommunicationssystemImpulsenoiseistheprimarysourceoferrorindigitaldatacommunicationCrosstalkCrosstalkItisthemostimportantofthecapacitylimitingnoiseItiscausedbyelectromagneticradiationofotherphonelinesincloseproximityormaybefromwithinthesamecableThecrosstalkwilldecreaseasthebandwidthincreasesThecloserthedifferentwiresgettoeachotherthestrongerthecouplingincreasesThecrosstalkistypicallyworsebetweentwopairsinthesamebinderthanintheadjacentbindersThecrosstalktransferfunctionwillbedifferentineachpaircorrespondingtothegeometricdifferencesofabindergroupCrosstalkmaybeminimizedbyusingthetwistedpairbeforetwistingthepairsintobindergroupsWhat'sspecialaboutxDSLWhat'sspecialaboutxDSLcablesconnectinghouseholdstophonenetworkaresimpletwistedpaircopperwiresModemspeedshavegraduallyincreasedthroughtheuseofvariouscompressionandothertechniquesDSLtechnologyenablesmuchhigherspeeds,speedsuptoMegabitspersecondormoretimesfasterDSLhasitsownkindof"modems"technologyallowsthenetworktomanagetrafficratherthanallocatingcompleteendtoendcircuits,userperspectivedataconnectionis"alwayson"xDSLdeploymenttohomesmakeeasierforInternetconnectionscanbesoldonafixedrate"permonth"encouraginguseofInternet,ecommerce,teleworkingetc TypesofxDSLTypesofxDSLADSL(AsymmetricDigitalSubscriberLine)GLiteorDSLLite(knownasDSLLite,splitterlessADSL,andUniversalADSL)HDSL(HighbitrateDSL)RADSL(RateAdaptiveDSL)SDSL(SymmetricDSL)UDSL(UnidirectionalDSL)VDSL(VeryhighdatarateDSL)xDSLADSL(AsymmetricDigitalSubscriberLine)ADSL(AsymmetricDigitalSubscriberLine)"asymmetric"twowayorduplexbandwidthisdevotedtothedownstreamdirection,sendingdatatotheusersmallportionofbandwidthisavailableforupstreamoruserinteractionmessagesmostInternetandmultimedianeedlotsofdownstreambandwidthmegabitspersecondofdatacanbesentdownstreamanduptoKbpsupstreamhighdownstreambandwidthmeansabletobringmotionvideo,audio,andDimagestoyourcomputerorTVsetGLiteorDSLLite(DSLLite,splitterlessADSL,andUniversalADSL)GLiteorDSLLite(DSLLite,splitterlessADSL,andUniversalADSL)essentiallyaslowerADSLthatdoesn'trequiresplittingofthelineattheuserendbutmanagestosplititfortheuserremotelyatthetelephonecompanyofficiallyITUTstandardG,providesadataratefromMbpstoMpbsdownstreamandfromKbpstoKbpsupstreamexpectedtobecomethemostwidelyinstalledformofDSLThedifferentDSLtechnologiesThedifferentDSLtechnologiesHDSLandSDSLareusedforsymmetricservicesespeciallyforbusinessesADSLusefulforasymmetricservicetoresidentialserviceswhileVDSLprovidesthechoicesforasymmetricorsymmetricforbusinessorresidentialservicesVDSLalsoupdatedstandardforprogrammablesymmetricdataratesinthexDSLtechnologiesDSLtechnologiesstillevolvingperformanceoffunctionality,levelsofintegration,andspeed AxDSLSummaryTableAxDSLSummaryTableADSLNetworkDesignADSLNetworkDesignDesignanxDSLNetworkDesignArchitecturefortheNetworkLocateresidentialusersbyplottingpointsonthegridMakeAssumptionsontheTrafficSpecificationADSLNetworkDesignArchitectureADSLNetworkDesignArchitecturewedesignedanotherlayerRemoteUnitbetweentheCOandendsubscribersThisRemoteDSLsolutionisenableserviceproviderstocosteffectivelyextendasymmetricdigitalsubscriberline(ADSL)servicestonewareasandintroducenewhighbandwidthpremiumservicesAlsoprovidealowdeploymentcostforsmallplatformsandfacilitateADSLNetworkDesignArchitectureADSLNetworkDesignArchitectureADSLNetworkDesignArchitectureADSLNetworkDesignArchitectureADSLNetworkDesignCentralOfficeDSLAMDeploymentADSLNetworkDesignCentralOfficeDSLAMDeploymentDescriptionandAssumptionsVoiceTrafficSpecificationDescriptionandAssumptionsVoiceTrafficSpecificationPhoneusageassumptionsandmeasurementVoiceTraffic:EpersubscriberInternationalCalls:Localcalls:CallsroutedtoLineBusy:CallsroutedtoNoanswer:CallsroutedtoAnnouncement:BasedontheaboveusagemeasurementandassumptionthenumberofvoicetrafficequipmentsontheCentralofficecanbecalculatedWehavefollowingassumptionsDSLAMcapacity:subscribersBandwidthofOCline:MbpsBandwidthofOCline:MbpsUsingthisdata,wecalculateandgetresultasfollowEffectiveBandwidth:d=mc(Ploss=–)DescriptionandAssumptionsVoiceTrafficSpecificationDescriptionandAssumptionsVoiceTrafficSpecificationDescriptionandAssumptionsVoiceTrafficSpecificationTheassumptionsofInternettraffic,fileusage,andemailusageareshownastable:NetworkEquipmentSpecificationVoiceEquipmentCostNetworkEquipmentSpecificationVoiceEquipmentCostLineCardCost:$DigitoneReceiver:$RingingCircuit:$BusyToneCircuit:$AnnouncementCircuit:$Trunk:$SwitchPort:$CentralComputer:$SLC:$perlineAnnualCostforADSLproviderAnnualCostforADSLproviderDSLAMChassisCost:$DSLAMModemsubscriber:$Subscriberschassis:Numberofchassisdeployed:chassis(K)TotalnumberofADSLportsdeployed:,TotalDSLAMCosts:$x$x,=$,,ServiceAggregationCosts:$AnnualCostforADSLproviderAnnualCostforADSLproviderTotalServiceAggregationCostwithOverhead:$,,AnnualCostperOCline:$,AnnualCostperOCline:$,AnnualCostperDSline:$,SubscribersDSLAM:NumberofOCsfromDSLAMtoMultiplexer:CostofMultiplexer:$CostofATMSwitchatCO(CiscoLightStreamSupportsOClines):$,Monthlyexpensepercustomer=TotalAnnualCosts(*X) ADSLVariablesandFaultDomainsADSLVariablesandFaultDomainsADSLFutureADSLFutureADSLiscompetingwithcablemodem,satelliteInternetapproximately,householdsuseADSLin,comparedto,,householdswithcablemodemsBy,IDCestimatescablemodemsrisento,,,whileDSLrisento,,householdsADSLislimited(byUSFederalCommunicationsCommissionregulations)toamaximumofmegabitspersecondCurrenttechnologycanprovideatheoreticalmaximumofuptomegabitspersecond,researchpromisesgreaterperformancewithprotocolslikeGLiteandVDSLADSLGrowthADSLGrowthDecember–MarchWorldwideDSLsubscribersIncreaseinADSLworldwideADSLResidentialSubscribersADSLResidentialSubscribers‘NorthAmerica,LatinAmericaWesternEurope,EasternEuropeSouthandEastAsiaAsiaPacific,MiddleEastandAfricaTotalMarchADSLBusinessSubscribersADSLBusinessSubscribers‘NorthAmerica,LatinAmericaWesternEuropeEasternEuropeSouthandEastAsiaAsiaPacificMiddleEastandAfricaTotal,MarchPercentageGrowthByRegionPercentageGrowthByRegionRegionSubscribers(s)GrowthNorthAmericaSouthEastAsiaAsiaPacificWesternEuropeLatinAmericaEasternEuropeMiddleEastAfricaTotalSubscribersTotalSubscribersConclusionConclusionThefuturelooksbrightforADSLWhileyesterday'sobstaclesandnegativepredictionsfadeaway,manyarewatchingADSLwithrenewedinterestThe"needforspeed"isincreasing,andtheADSLindustryisworkinghardtomakesurethatbroadbandADSLcontinuestobetheglobalchoice

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