Classification
Infatti, non esiste una definizione rigida. In generale, il limite superiore della velocità di accesso a Internet dial-up è di 56 Kbps. Il metodo di accesso è classificato come "banda larga".
Fromtheperspectiveofbroadbandaccessmedia,itcanbedividedintotwocategories,oneiswiredbroadbandaccess,andtheotheriswirelessbroadbandaccess.
Type
ADSL
Definition:ADSListheEnglishabbreviationofAsymmetricalDigitalSubscriberLoopinEnglish,ADSLtechnologyisanewhigh-speedbroadbandtechnologythatrunsontheoriginalordinarytelephoneline.Itusesanexistingpairoftelephonecopperwirestoprovideuserswithasymmetricaltransmissionrate(bandwidth)foruplinkanddownlink.Theasymmetryismainlyreflectedintheasymmetrybetweentheuplinkrate(upto640Kbps)andthedownlinkrate(upto8Mbps).Uplink(fromusertonetwork)islow-speedtransmission,upto640Kbps;downlink(fromnetworktouser)ishigh-speedtransmission,upto8Mbps.Itwasoriginallydevelopedmainlyforvideo-on-demandservices.Withthedevelopmentoftechnology,ithasgraduallybecomeamoreconvenientbroadbandaccesstechnology,whichisvaluedbythetelecommunicationssector.Throughtheset-topboxofnetworkTV,manynetworkapplicationsthatcouldnotberealizedatlowspeedcanberealizedbefore.ADSListhemostsuitabletechnologyforbroadbandInternetaccessinthecurrentDSLtechnologyseries.Becauseoftheasymmetriccharacteristicsoftheupstreamanddownstreamrates,therateandthetransmissiondistanceofADSL,itmeetstherequirementsofInternetaccessatthisstage,anditcansharetheaccesslinewithordinaryphones.;ThestandardizationofADSLisverycomplete,theinteroperabilityofproductsisverygood,thepriceisdroppingsharply,andADSLaccesscanprovideQoS,ensurethatuserscanenjoyacertainbandwidthexclusively.BeijingTelecombegantoconductADSLservicetrialsin1999.In2001,itcarriedoutlarge-scalenetworkconstruction.In2002,itincreaseditsmarketexpansion.In2003,thenumberofusersincreasedsignificantly,exceeding600,000.Itisexpectedthatthenumberofuserswilldoublenextyear..
Developmentproblems:Developmentproblemsincludecablequalityandcrosstalk,whichwillseriouslyaffecttheopeningrateofADSL.Forthisreason,DSLAMneedstobecontinuouslypromotedtotheusersidebyshorteningtheaccessDistancetosolvethecrosstalkproblemofADSL.Inaddition,thetransmissionrateofADSLislimitedafterall,whichcannotmatchhigh-speedaccesstechnologiessuchasfiberaccessandFTTx+LAN.TheasymmetryofADSLwillalsoseverelyrestrictthedevelopmentofinteractivemultimediaservices.InordertosolvesomeoftheproblemsofADSL,ADSLtechnologyitselfisconstantlyimproving.InJuly2002,theITUreleasedtwonewADSLstandards0.99.2andG.992.4,alsoknownasADSL2.InMarch2003,theITUformulatedG.992.5,whichisADSL2+.ComparedwithADSL,thefunctionsandperformanceofADSL2arefurtherstrengthened.ADSL2usesthesamefrequencybandasADSL,soitstheoreticalmaximumtransmissionrateandtransmissiondistancearenotsignificantlydifferentfromADSL.ADSL2+hasfurtherexpandedtheavailablefrequencybandsanduplinkanddownlinktransmissionrates,anditsmaximumdownlinkrateatshortdistancescanreachmorethan25Mbit/s.AsADSL2/ADSL2+issuperiortoADSLinperformanceandfunctions,itwillinevitablybecomeanimportantdevelopmentdirectionforcopperwirebroadbandaccessinthefuture,anditsproductshavebeguntoenterthemarket.
VDSListhehighest-speedDSLtechnology.Itcanprovidesymmetricalandasymmetricalmodes.VDSLequipmentthatcanachieveatwo-waysymmetricalllMratewithintherangeoflkmhasbeenwidelycommercializedandiscalledEthernetonthetelephoneline.Networktechnology.Thistechnologyisverymeaningfulforservicesthatrequirehigh-speedorsymmetricaltransmission.VDSLcanreplaceFTTx+LANaccesstechnologyinacertainrange,avoidalargeamountofinvestmentinintegratedwiring,andcanbecomeanimportantmeansfortraditionaloperatorstocounteremergingoperators'Ethernetaccess.BeijingTelecomhasadoptedVDSLtechnologyonasmallscale.
ORA
Definition:chinacablemodemcablemodemisalsoknownascablemodem,commonlyknownascablemodem,anditsEnglishnameisCableModem.Developedwiththeexpansionofnetworkapplications,itismainlyusedfordatatransmissionincabletelevisionnetworks.
Accessmethod:CableTVcompaniesgenerallyseparatea6MHZchannelfromtheTVchannelsbetween42MHZ～750MHZfordownlinktransmissionofdata.Usuallythedownlinkdataadopts64QAM(quadratureamplitudemodulation)modulationmode,thehighestratecanreach27Mbps,ifadopts256QAM,thehighestratecanreach36Mbps.Uplinkdataisgenerallytransmittedthroughasectionoffrequencyspectrumbetween5and42MHZ.Inordertoeffectivelysuppresstheaccumulationofuplinknoise,QPSKmodulationisgenerallyselected.QPSKismoresuitablefornoiseenvironmentsthan64QAM,buttherateislower.Uplinkspeedcanreachupto10Mbps.
Development:CableModemaccesstechnologyisdevelopingrapidlyintheworld,especiallyinNorthAmerica.Thenumberofusersisgrowingatarateofover100%eachyear.InChina,thereareShenzhen,NanjingandotherprovincesandcitieshaveopenedCableModemaccess.Itisthebiggestcompetitorofthetelecommunicationcompany'sxDSLtechnology.Inthefuture,thexDSLaccesstechnologybasedontraditionaltelephonenetworksdevelopedvigorouslybythetelecommunicationcompanycampandtheCableModemtechnologypromotedbythebroadcastingsystemandcableTVmanufacturerswillcompetefiercelyintheaccessnetworkmarket(especiallythehigh-speedInternetaccessmarket).InChina,thebroadbandaccesstechnologydevelopedbytheradioandtelevisiondepartmentonthecabletelevision(CATV)networkhasmaturedandenteredthemarket.TheCATVnetworkhasawidecoverageareaandalargenumberofusers(accordingtostatistics,thenumberofcableTVusersnationwidehasexceeded100millioninJanuary1999);thenetworkhasawidespectrumrangeandahighstartingpoint.Mostnewly-builtCATVnetworksuseopticalfibercoaxialHybridnetwork(HFCnetwork),usingadjacentfrequencytransmissionsystemwithbandwidthabove550MHZ,isverysuitableforprovidingbroadbandfunctionalservices.CableModem(CableModem)technologyisanetworkaccesstechnologybasedonCATV(HFC)network.
CableModemcompletelysolvesthecongestioncausedbythetransmissionofsoundandimage,anditsratehasreachedmorethan10Mbps,andthedownstreamrateisevenhigher.Althoughthetraditionalmodemhasdevelopedaproductwitharateof56Kbps,itstheoreticaltransmissionlimitis64Kbps,anditisimpossibletoincreaseit.
CableModemisalsoakeydeviceforbuildingametropolitanareanetwork.Hybridopticalfibercoaxialnetwork(HFC)backboneusesopticalfiber,andtree-typebuscoaxialcablenetworkisusedtoconnectusersinopticalnodecommunities.ItstransmissionfrequencyItcanbeashighas550/750MHz.ItisnecessarytouseCableModemtotransmitdatainHFCnetwork.
WecanseethatCableModemisamust-haveforfuturenetworkdevelopment.However,thereisnointernationalstandardforCableModem,andthetransmissionratesofproductsfromvariousmanufacturersaredifferent.Therefore,theestablishmentofthebroadbandaccessnetworkofthehigh-speedmetropolitanareanetworkhasyettobereleasedbytheCableModemstandard.
DSL
DSL(DigitalSubscriberLineDigitalSubscriberLine)technologyisabroadbandaccesstechnologybasedonordinarytelephonelines.Ittransmitsdataandvoicesignalsseparatelyonthesamecopperwire.Thedatasignaldoesnotpassthroughthetelephoneswitchequipment,whichreducestheloadofthetelephoneswitch;andthereisnoneedfordial-up,anditisalwaysonline,whichbelongstothewayofdedicatedlineInternetaccess.DSLincludesADSL,RADSL,HDSL,VDSLandsoon.
VDSL
VDSL (summa-bit-rateDigitalSubscriberloop)isa high-speeddigitalsubscriberloop.Simplyput, VDSLisafastversion of ADSL.Using VDSL,maximum-downloadrate with inshortdistance canreach55Mbps,et uploadratecanreach19.2Mbps,orevenhigher.
Featuresofopticalfiber:Opticalfiberhastheadvantagesofbroadband,stronglong-distancetransmissionability,goodconfidentiality,andstronganti-interferenceability.Itisthemainrealizationtechnologyofaccessnetworkinthefuture.TheFTTHmethodreferstothefiberpass-throughuser'shome,generallyonlyoneortwosubscriberlinesareneeded.Theeconomyisnotgoodintheshortterm,butitisalong-termdevelopmentplan!
FTTX+LAN
Accessmethod:ThisisabroadbandaccesssolutionthatusesopticalfiberplusCategory5networkcabletorealizegigabitopticalfiberTothecentralswitchofthecommunity(building),thecentralswitchandthecorridorswitchareconnectedby100MopticalfiberorCategory5networkcable,integratedwiringisadoptedinthecorridor,theuser'sInternetspeedisunlimited,thenetworkisexpandable,andtheinvestmentscaleissmall.Inaddition,therearemultipleaccessmethodssuchasfibertotheoffice,fibertothehome,fibertothedesktoptomeettheneedsofdifferentusers.TheFTTX+LANmodeusesastarnetworktopology,anduserssharebandwidth.TheuseofEthernetaccess(ieFTTx+LAN)afterthefiberreachesthebuildingorresidentialareaisawidelyoptimisticandcontroversialbroadbandaccessmethod.EthernetaccessusesCategory5unshieldedtwistedpair(UTP)astheaccessline,whichrequiresintegratedwiringinthebuilding.Ethernetalmostdominatestheworldinthelocalareanetwork.AfterintroducingEthernettotheaccessnetworkoreventhemetropolitanareanetwork,thesametechnologycanbecompletelyadoptedfromtheuserdesktop,accessnetworktothecorenetwork,avoidingtheproblemscausedbyprotocolconversion.Ethernetaccesshastheadvantagesofgoodscalability,lowprice,highaccessrate,andmatureandsimpletechnology.Itcanprovideuserswithaterminalaccessrateof10/100M.Especiallyforhigh-densityusergroups,theeconomyofEthernetaccessisalsoverygood,andduetothehighresidentialdensityofurbanresidentsinmycountry,itisjustsuitableforthisfeatureofEthernetaccess.Asaresult,ourcountrysetoffaclimaxofEthernetaccessconstructionfrom2000to2001.Inparticular,manyemergingbroadbandaccessserviceprovidershaveadoptedthemethodofcooperatingwithcommunitiestoprovideFTTx+LANbroadbandaccessservicesoneafteranother,startingfromahighstartingpoint.Confrontingtraditionaloperators'ADSLaccess.InBeijing,broadbandservicecompaniessuchasChangkuanandLanbousedthistechnologytoactivelycompeteforthebroadbandaccessmarket.Subsequently,traditionaloperatorssuchasBeijingTelecomalsoquicklyfollowedupandcooperatedwithrealestatedeveloperstofullyimplementintegratedwiringformanynewlybuiltcommunities.DeploytheEthernetsockettoeveryfamily,andsoonoccupyadominantpositioninthismarket.
However,becauseEthernettechnologyisdevelopedforLANapplicationsafterall,afterbeingappliedtotheaccessnetworkenvironmentofserviceproviders,manyproblemsaregraduallyexposed,suchastheneedtosolveusercontrolandmanagement,userauthenticationFormanyissuessuchasbilling,userisolationandsecurityassurance,businessmanagement,serviceleveldifferentiation,equipmentandnetworkmanagement,andequipmentpowersupply,manyequipmentvendorshaveintroducedvariousproprietarysolutionstoadapttooperators’accessnetworkapplications.TheEthernetspecificationsofthecompanyarealsograduallybeingformulated,butingeneral,veryidealEthernetaccessproductsandsolutionsthatcanmeettherequirementsofcarrier-leveloperationsarestilllacking,andrelatedstandardsneedtobeimproved.Inaddition,duetothelowinstallationrateintheactualenvironment,thereturnoninvestmentisoftenpoor.AlargenumberofEthernetswitchesareinstalledinuserbuildings,whichalsobringsmanyproblemstomaintenanceandmanagement.AlthoughEthernetaccesscanprovideeachuserwitha10Mbit/sinterfacerate,infact,itisdifficultforordinaryuserstotrulyenjoythe10Mbit/sInternetrateatthisstage,becausethebandwidthsharedbythecommunitybroadbanduserstoentertheInternetbackboneisoftenVerylimited.ThisseriesofproblemshinderedthesmoothdevelopmentofFTTx+LAN,andmadeADSLquicklyoccupythedominantpositionofbroadbandaccess.
SDHpoint-ad-punctum
SDHpoint-ad-pointtopologymap (3sheets)
Definition:DigitalPrivateLine(SDH):TheEnglishnameisSDH(SynchronousDigitalHierarchy)dedicatedline,andtheChinesenameisdigitaldedicatedline.Itisadatatransmissionservicethatusesopticalfiber,digitalmicrowave,satelliteandotherdigitalcircuitstoopen.Itusesadigitaltransmissionchanneltotransmitdatasignalsinacommunicationnetwork,andcanprovidedataleasedcircuitsforpoint-to-pointandpoint-to-multipointtransparenttransmissiontotransmitdata,images,soundandotherinformationtousers.Features:SDHpoint-ad-punctumhastheadvantagesofconvenientupperandlowercircuits,strongmaintenance,control,andmanagementcapabilities,unifiedstandards,andeaseoftransmissionofhigherrateservices.
Proin
Proinaccessisacommunicationmethodthatusesmicrowavetotransmitinformationwirelessly.Digitalmicrowavecommunicationusesdigitalsignalprocessingtechnologyinmicrowavetransmission,whichnotonlyhasthecharacteristicsoffastconstructionofmicrowavecommunicationandflexibleapplication,butalsohasmanyadvantagessuchasreliabletransmissionquality,stronganti-interferenceability,andlongtransmissionlines.Sofar,ithasbeenlistedasthethreepillarsofmoderncommunicationtransmissionalongsideopticalfiberaccessandsatellitecommunications.Amongmedium-capacitynetworks,microwaveaccessnetworksarethemostflexibleandadaptablecommunicationmeans.Thedemandformicrowaveproductsintheglobalmarketisincreasingsteadily,especiallyintelecommunicationnetworks,privatenetworksandbroadbanddatanetworks.
Openingupthemarket
InNovember2014,theMinistryofIndustryandInformationTechnologyissuedthe"OpinionsonOpeningUptheBroadbandAccessMarket(DraftforComment)",whichrequiresthatprivatecapitalbeencouragedThismodelentersthebroadbandaccessmarketandpromotesthedevelopmentofbroadbandnetworkinfrastructureandtheimprovementofbusinessservicelevels.Thefirst16pilotcitiestoopenthebroadbandaccessmarketare:Taiyuan,Shenyang,Harbin,Shanghai,Nanjing,Hangzhou,Ningbo,Xiamen,Qingdao,Zhengzhou,Wuhan,Changsha,Guangzhou,Shenzhen,Chongqing,andChengdu.Thepilotperiodis3year.
The"DraftofOpinions"proposesthatpilotenterprisescanbuildallorpartofthewiredcommunicationnetworkfacilitiesfromtheuserendtothenetworkaccessserver,andcancarryouttherentalandsaleofcorrespondingnetworkelements.PilotenterprisesthathaveenteredservicebusinesslicensescanalsoprovidebroadbandInternetservicestoenduserswiththeirownbrands.