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VDSL2A feasible Solution for “Last Mile”

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Version Date Author ApprovedBy Remarks

V1.00 �009-08-�8 MichaelSong NotopentotheThirdParty

©�009ZTECorporation.Allrightsreserved.ZTECONFIDENTIAL:ThisdocumentcontainsproprietaryinformationofZTEandisnottobedisclosedorusedwithoutthepriorwrittenpermissionofZTE.DuetoupdateandimprovementofZTEproductsandtechnologies,informationinthisdocumentissubjectedtochangewithoutnotice.

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Content TABLE OF CONTENTS1 Brief Introduction of VDSL2………………………………………………………………1

2 VDSL2 Standard……………………………………………………………………………1

�.1ITU-TG.99�.1…………………………………………………………………………………1

�.�ITU-TG.99�.�…………………………………………………………………………………1

�.�ITU-TG.994.1…………………………………………………………………………………�

�.4BroadbandForumTR-1�9…………………………………………………………………�

�.5BroadbandForumTR-165…………………………………………………………………�

3 VDSL2 Technology…………………………………………………………………………4

�.1VDSL�Profiles………………………………………………………………………………4

�.�DMTModulation………………………………………………………………………………5

�.�BandPlans……………………………………………………………………………………6

�.4Duplexing……………………………………………………………………………………7

4 VDSL2 Deployment Modes………………………………………………………………8

FIGURESFigure1TR-1�9ManagementModel…………………………………………………………�

Figure 2 Vector of Profile Model…………………………………………………………………3

Figure�DiscreteMultitone(DMT)………………………………………………………………5

Figure4ADSL/ADSL�/ADSL�+FrequencyAllocation………………………………………6

Figure5BandPlansofVDSL1andVDSL�……………………………………………………6

Figure6The“Zipper”Principle…………………………………………………………………7

Figure7CyclicExtension………………………………………………………………………8

Figure8VDSL�DeploymentScenarios………………………………………………………8

Figure 9 VDSL2 Profiles for Different Deployment Mode……………………………………9

TABLESTable1VDSL�Profiles…………………………………………………………………………4

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1 Brief Introduction of VDSL2ADSL�plus iscurrentlybeingdeployedworldwideasthenewmainstreambroadbandtechnologyforresidentialandbusinesscustomers.Butatthesametime,theindustryisgearingupforthenextstepoftheDSLevolution:VDSL�.Thissecondversionoftheveryhigh-speeddigitalsubscriberline(VDSL)standardfromITU-Tpromisestodeliver100Mbpssymmetricaltrafficonshortcopperloops.ThegreaterbandwidthofVDSL�givestelecommunicationsoperatorstheabilitytoofferadvancedservicessuchasmultiplestreamsof interactivestandardandhigh-definitionTVover IPover theexistingcopperplant.TVservicesarefastbecomingstrategically important totelecommunicationoperatorswhoarecompetinghead-to-headwithcableoperatorslaunchingvoiceoverIP(VoIP)andhigh-speedinternetservices.ITUbegandrafting itsVDSL�standard(G.99�.�) inJanuary�004.Consensus for thestandardwasreachedatameetinginGenevainMay�005.AswithADSL/�/plus,theunderlyingmodulationintheVDSL�standardisdiscretemultitone(DMT).VDSL�isbasedonboththeVDSL1-DMTandADSL�/ADSL�plusrecommendations.Therefore, it isspectrallycompatiblewithexistingservicesandenablesmultimodeoperabilitywithADSL/�/plus.VDSL�extendthespectrumto�0MHzandcandeliver�00Mbpssymmetricaltrafficonshortcopperloopsatmost.

2 VDSL2 Standard2.1 ITU-T G.993.1ITU-T G.99�.1 VDSL (very high-speed digital subscriber line) standard, defined the firstgenerationVDSLsystemmodel, interfacerequirements,performancerequirements,managementrequirements,power supply requirements, security requirementsand transceiver technicalrequirements.Thisversionof theveryhigh-speeddigitalsubscriber line (VDSL)standard fromITU-Tpromisestodeliver55Mbpsdownstreambandwidthand19.�Mbpsupstreambandwidthonshortcopperloops.

2.2 ITU-T G.993.2VDSL�enhanced ITU-TG.99�.1VDSL technology,which supports 100Mbps symmetricalbandwidthonshort copper loops.VDSL�definedDMTmodulation technology,andmade itpossiblethatprovidereliablehighspeeddatatransmissiononshortcopper loopsbyuse�0MHzspectrumband.VDSL�supportsTrellisCodedforcibly,andadoptsUS0band,EchoCanceller,andTimeequalizers(TEQs),soVDSL�canworkstablyonabout�500mlength�6AWGcopperloops(0.4mm).

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G.99�.�definedalltheparameterswhichVDSL�transceivermaybesupports(suchasbandwidthand transceiverpower).Otherwise,G.99�.�alsodefinedmany itemswhichmakevendorscanreducecomplexityofproductsanddevelopsuitablesolutions for real services requirement.Someitemsaresuitforsymmetricaldataspeedservices;othersareforasymmetricaldataspeedservices.G.99�.�accessoryincludesbandplanningandpowerspectrumdensity(PSD),anddefinedregionalspecialrequirements.ComparewithITU-TG.99�.1,G.99�.�hasthefollowingchanges:●Carrierfrequencyupto�0MHz,bidirectionaldataspeedupto�00Mbit/s;●ExtendtheupperlimitofUS0bandto�76kHz;●Echocancellerandtimeequalizers(TEQs)areusedtoimproveUS0performance;●Widelyapplicationscenarios(CO,Cabinet,Building,etc.);●Downstreamtransmissionpowerupto�0.5dBm;●SupportsTrellisCodedforcibly;●Supportsallintegralconstellationsfrom1bitto15bit;●Supportsrandomcycledextension;●Supportsallintegralimpulsenoiseprotection(INP)whichcanhave16charactersatmost;●Enhancedonlinereconfiguration(OLR);●Enhancedframingfunction;●Enhancedoverheadchannel;●Enhancedinterlacing;●EnhancedFECfunction;●Definedtwowaitingtimepathsandtwobearerchannels;●Improvedinitializationprocess,includechanneldiscoveryphase,trainingphase,channelanalysis

andswitchingphase;●SupportsVTU-Rduringinitializationphase;●Supportsabundanttestingparameters;●Definedloopdiagnosismode;●SupportsSTMinterface;●SupportsPTMinterfacewhichbaseonIEEE80�.�ah64/65bytepackage.

2.3 ITU-T G.994.1G.994.1 is the common handshaking or activation procedure for DSL modems. It is fullyinteroperablewiththeactivationprocedureforT1.41�DSLmodemsbutoffersseveralbenefitsforserviceproviders:robustness,exchangeofcapabilities information,notificationof theapplicationandservicerequests,backwardsandforwardscompatibilityforotherDSLmodemstandards,etc.PreviousgenerationDSLmodemsreliedonsingletonestonegotiatethemodemoperatingoptionsduringstartup.WithG.994.1,simultaneousmultipleredundantsetsoftonesaremodulatedwith

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digital information.Ifoneormoretonesareblockedbyinterferingnoise,bridgetapsorotherwiseunavailable,atleastonewillbeavailabletocompletethestartupinformationexchange.Thetoneswereselectedandtheproceduresweredesignedtobecompatiblewith themanyotherexistingservicesincludingotherDSLsinthenetwork.Thedigital informationcarriedbyG.994.1cannowgobeyond thesimpleselectionofoptionsinpreviousgenerationDSLmodemstartupprocedures.Higher layersoneachendof theDSLmodemscan indicateserviceandapplication requirementsduring thehandshakeso that theappropriateDSLRecommendation from the familyofDSL recommendationswillbeactivatedfollowing theG.994.1handshake.Thisallowsproviders to flexibly tailor theservicebandwidthand latency requirementsof thecustomer'sdynamicapplicationsandenvironments includingmobileDSLmodemsormodempooling.TheG.994.1dataarchitectureisflexibleenoughtoallowexchangeofnewornon-standardinformationwithoutupgradingtheinstalledsoftwarebase.

2.4 Broadband Forum TR-129TR-1�9 isdefinedbyBroadband forum,DSL forumhasrenamedtoBroadband forum.TR-1�9managementmodelsuitsforADSL,ADSL�,ADSL�+,VDSL�technologies.

Figure1TR-1�9ManagementModel

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2.5 Broadband Forum TR-165TR-165 isVectorofProfilestandardwhichdefinedbyBroadbandforum.TR-165was improvedbaseonTR-1�9tomakemanagementeasier.

Figure�VectorofProfileModel

3 VDSL2 Technology3.1VDSL2ProfilesG.99�.�definesawiderangeofsettingsforvariousparametersthatcouldpotentiallybesupportedbyaVDSL� transceiver.Profilesarespecified toallow transceivers tosupportasubsetof theallowedsettings.Thespecificationofmultipleprofilesallowsvendors to limit implementationcomplexityanddevelopimplementationsthattargetspecificservicerequirements.VDSL� transceiversshall complywithat leastoneprofilespecified inG.99�.�.Compliancewithmore thanoneprofile isallowed. Inaddition tocomplyingwithat leastoneprofile,VDSL�transceiversshallcomplywithatleastoneannexspecifyingspectralcharacteristics.TheeightVDSL�profiles(8a,8b,8c,8d,1�a,1�b,17a,and�0a)aredefinedinTable1.

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Profile 8a 8b 8c 8c 1�a 1�b 17a �0a

Bandwidth(kHz) 8,8�� 8,8�� 8,8�� 8,8�� 1�,000 1�,000 17,664 �0,000

Subchannel �048 �048 �048 �048 �78� �78� 4096 �479Subchannel

Spacing(kHz）4.�1�5 4.�1�5 4.�1�5 4.�1�5 4.�1�5 4.�1�5 4.�1�5 8.6�5

Minimumbi-directionnet

dataratecapacibility

50Mbps 50Mbps 50Mbps 50Mbps 68Mbps 68Mbps 100Mbps �00Mbps

Aggregateinterleaverandde-interleaverdelay(octets)

64k 64k 64k 64k 64k 64k 96k 1�8k

Maximuminterleaving

(octets)�048 �048 �048 �048 �048 �048 �07� 4096

Parameter(1/S)max

downstream�4 �4 �4 �4 �4 �4 48 �8

Parameter(1/S)maxupstream

1� 1� 1� 1� 1� �4 �4 �8

SupportofUS0 YES YES YES YES YES NO NO NO

DS/USPower（dbm）

+17.5/+14.5

+�0.5/+14.5

+11.5/+14.5

+14.5/+14.5

+14.5/+14.5

+14.5/+14.5

+14.5/+14.5

+14.5/+14.5

Table1 VDSL�Profiles

3.2 DMT ModulationDMTmodulationusesthesameprincipleasorthogonal frequency-divisionmultiplexing(OFDM).6That is, itdivides theuseful frequencyspectra intoparallelchannels,where thecenterofeachchannel isrepresentedbyamodulated(QAM)subcarrier(Figure�).OnedifferencefromOFDMisthateachcarrierinDMTcanbeloadedwithadifferentnumberofbits,dependingonthesignaltonoiseratio(SNR). InOFDM,theconstellationsizeofeachcarrier is thesame.Becauseeachsubcarrierisorthogonaltotheothersubcarriers,thereisnointerferencebetweensubcarriers.Thenumberofbitscanbevariedbetween1and15.Thedistancebetweensubcarriersis4.�1�5kHz.InVDSL�adistanceof8.61�5kHzmayalsobeused.InversefastFouriertransform(IFFT)isusedtogeneratethesubcarriers.

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3.3 Band PlansADSLcanbedescribedasatwo-bandsystemwhereonepartofthefrequencyspectrumisusedforupstreamtransmissionandthesecondpartisusedfordownstreamtransmission(Figure4).VDSL,ontheotherhand,usesmultiplebandsforupstreamanddownstreamtransmissionstoenableagreaterdegreeofflexibilitywithregardstorateconfigurationsandsymmetrybetweenupstreamanddownstreamdata.

Figure�DiscreteMultitone(DMT)

Figure4ADSL/ADSL�/ADSL�+FrequencyAllocation

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Twobandplansweredefined(in�000) tomeetoperatorrequirementsforsymmetry/asymmetry(Figure5).Thefirstofthese,BandPlan998,betterfacilitatesasymmetricservices,whereasBandPlan997accommodatessymmetricservices.VDSL1supportsabandwidthofup to1�MHz; inVDSL� thiscanbeextended to�0MHz.TobespectrallycompatiblewithVDSL1,VDSL�usesthesamebandplansbelow1�MHz.VDSL�canemployupto4,096subcarriers.Dependingonthebandplan inuse,asubcarrier isdesignatedforeitherupstreamtransmissionordownstreamtransmission.AsinADSL,thelowerpartofthespectraisallocatedforPOTSandISDNserviceandasplitter filter isusedtoseparatethePOTSorISDNfrequenciesfromtheVDSL�band.An“alldigitalmodes”optionalsoexists,wherevirtuallyallthespectracanbeusedforVDSL�.

Figure5BandPlansofVDSL1andVDSL�

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However,requirementsforspectralcompatibilitywithexistingDSLtechnologiesrequirenecessitatethatseveral tonesmustbegrouped into transmissionbands.OnecanpreservetheorthogonallybetweenthereceivedsignalandthetransmittedsignalechoedbackintothereceiverbycyclicallyextendingthetransmittedDMTsymbolsusingacyclicprefixandcyclicsuffixandbysynchronizingthe transmittersateachend tobegin transmittingat thesame time(a techniquecalled timingadvance).Cyclicextension,whicheliminatesintersymbolinterference(ISI)causedbythechannel,reducesthedatarateby7.8%.Windowing,atechniqueforsuppressingsidelobes,furtherreducesspectralleakagebetweentransmissionbands.WindowingisalsousedinOFDM(Figure7).

Figure6The“Zipper”Principle

Figure7CyclicExtension

3.4 DuplexingTodaydeploymentsofADSL/�/plususefrequency-divisionduplex(FDD) technology toseparatetheupstreambandfromthedownstreamband.Giventhephysicalproperties,however, it isnotpossible tocreatea“brickwall” transmissionband.That is, there isalwayssomespectralleakagebetweenthetransmissionbands.InADSL,filtersorechocancellersareusedtosuppressleakagebetweentransmissionbands.VDSL,ontheotherhand,usesadigitalduplexingtechniquebasedon the“zipper” technology inventedatTeliaResearch inLuleå.7With this technique,adjacentsubcarrierscarrydatainoppositedirections(Figure6).

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4 VDSL2 Deployment ModesTheVDSL�standard isdefinedusingsetsofprofiles,whereeachprofile targeta specificdeployment.Figure8depicts thedifferentdeploymentscenariosanticipated forVDSL�.Theseinclude:

Figure9VDSL�ProfilesforDifferentDeploymentMode

Figure8VDSL�DeploymentScenarios

●FibertotheNode(FTTN):VDSL�islocatedatthecentraloffice;●Fibertothecabinet(FTTCab):fiber-fedcabinetsarelocatednearcustomerpremises;●Fibertothebuilding(FTTB):VDSL�isplaced,forinstance,inthebasementofabuilding.Profiles8a-8band1�a-1�bapplytoFTTN;17aappliestoFTTCab;and�0a,toFTTB(Figure9).Eachprofilecontainssupportforunderlyingbasebandservices,suchasPOTSorISDN.

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