COMPUTER NETWORK 计算机网络英语论文.docx
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COMPUTER NETWORK 计算机网络英语论文.docx
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COMPUTERNETWORK计算机网络英语论文
计算机网络(双语)论文
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自动化工程学院
专业:
测控技术与仪器082
题目:
COMPUTERNETWORK
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Catalogue
Preface………………………………………………………3
Basics…………………………………………………………5
●Ultra-High-frequencycommunication(≥100MHz)…………………5
●Homenetworking(LAN)…………………………………………………6
●Internetaccess(broadbandoverpowerlines)……………………8
●Mediumfrequency(kHz)………………………………………………10
●Low-speednarrow-bandcommunication…………………11
●High-speednarrow-bandpowerlinecommunication —distributionlinecarrier……………………………………………………………13
●Transmittingradioprograms…………………………………………14
●Utilityapplications…………………………………………………15
●Lowfrequency( ●Broadbandoverpowerline(BPL)……………………………………17 ●'notchingout'anddynamicadaptationtocontention………………………………………………………………18 ●InterferenceissueremainsachallengetoPLCsystems………19 ●Automotiveuses…………………………………………………………21 ●FailureScenarios………………………………………………………21 ●IEEEP1901,ITUG.hnhomegrids……………………………………22 ●Standardsorganizations………………………………………………24 Smallandmedium-sizedenterpriseofficeLANconstructionscheme……………………………………………25 Personalfeeling…………………………………………30 Referencedirectory……………………………………………32 Preface Thisarticleisnowinitsfourthedition.Eacheditionhascorrespondedtoadifferentphaseinthewaycomputernetworkswereused.Whenthefirsteditionappearedin1980,networkswereanacademiccuriosity.Whenthesecondeditionappearedin1988,networkswereusedbyuniversitiesandlargebusinesses.Whenthethirdeditionappearedin1996,computernetworks,especiallytheInternet,hadbecomeadailyrealityformillionsofpeople.Thenewiteminthefourtheditionistherapidgrowthofwirelessnetworkinginmanyforms.Thenetworkingpicturehaschangedradicallysincethethirdedition.Inthemid-1990s,numerouskindsofLANsandWANsexisted,alongwithmultipleprotocolstacks.By2003,theonlywiredLANinwidespreadusewasEthernet,andvirtuallyallWANswereontheInternet. Accordingly,alargeamountofmaterialabouttheseoldernetworkshasbeenremoved.However,newdevelopmentsarealsoplentiful.Themostimportantisthehugeincreaseinwirelessnetworks,including802.11,wirelesslocalloops,2Gand3Gcellularnetworks,Bluetooth,WAP,i-mode,andothers.Accordingly,alargeamountofmaterialhasbeenaddedonwirelessnetworks.Anothernewly-importanttopicissecurity,soawholechapteronithasbeenadded. Manypeoplehelpedmeduringthecourseofthefourthedition.Iwouldespeciallyliketothankthefollowingpeople: RossAnderson,ElizabethBelding-Royer,SteveBellovin,ChatschikBisdikian,KeesBot,ScottBradner,JenniferBray,PatCain,EdFelten,WarwickFord,KevinFu,RonFulle,JimGeier,MarioGerla,NatalieGiroux,SteveHanna,JeffHayes,AmirHerzberg,PhilipHomburg,PhilippHoschka,DavidGreen,BartJacobs,FransKaashoek,SteveKent,RogerKermode,RobertKinicki,ShayKutten,RobLanphier,MarcusLeech,TomMaufer,BrentMiller,ShivakantMishra,ThomasNadeau,ShlomoOvadia,KavehPahlavan,RadiaPerlman,GuillaumePierre,WaynePleasant,PatrickPowell,ThomasRobertazzi,MedySanadidi,ChristianSchmutzer,HenningSchulzrinne,PaulSevinc,MihailSichitiu,BernardSklar,EdSkoudis,BobStrader,GeorgeSwallow,GeorgeThiruvathukal,PeterTomsu,PatrickVerkaik,DaveVittali,SpyrosVoulgaris,Jan-MarkWams,RuedigerWeis,BertWijnen,JosephWilkes,LeendertvanDoorn,andMaartenvanSteen.SpecialthanksgotoTrudyLevineforprovingthatgrandmotherscandoafinejobofreviewingtechnicalmaterial.ShivakantMishrathoughtofmanychallengingend-of-chapterproblems.AndyDornansuggestedadditionalreadingsforChap.9.JanLooyenprovidedessentialhardwareatacriticalmoment.Dr.F.deNiesdidanexpertcut-and-pastejobrightwhenitwasneeded.MyeditoratPrenticeHall,MaryFranz,providedmewithmorereadingmaterialthanIhadconsumedintheprevious7yearsandwashelpfulinnumerousotherwaysaswell.Finally,wecometothemostimportantpeople: Suzanne,Barbara,andMarvin.ToSuzanneforherlove,patience,andpicniclunches.ToBarbaraandMarvinforbeingfunandcheeryallthetime(exceptwhencomplainingaboutawfulcollegetextbooks,thuskeepingmeonmytoes). Basics Allpowerlinecommunicationssystemsoperatebyimpressingamodulatedcarriersignalonthewiringsystem.Differenttypesofpowerlinecommunicationsusedifferentfrequencybands,dependingonthesignaltransmissioncharacteristicsofthepowerwiringused.SincethepowerwiringsystemwasoriginallyintendedfortransmissionofACpower,inconventionaluse,thepowerwirecircuitshaveonlyalimitedabilitytocarryhigherfrequencies.Thepropagationproblemisalimitingfactorforeachtypeofpowerlinecommunications.AnewdiscoverycalledE-LinethatallowsasinglepowerconductoronanoverheadpowerlinetooperateasawaveguidetoprovidelowattenuationpropagationofRFthroughmicrowaveenergylineswhileprovidinginformationrateofmultipleGbpsisanexceptiontothislimitation. Dataratesoverapowerlinecommunicationsystemvarywidely.Low-frequency(about100-200 kHz)carriersimpressedonhigh-voltagetransmissionlinesmaycarryoneortwoanalogvoicecircuits,ortelemetryandcontrolcircuitswithanequivalentdatarateofafewhundredbitspersecond;however,thesecircuitsmaybemanymileslong.Higherdataratesgenerallyimplyshorterranges;alocalareanetworkoperatingatmillionsofbitspersecondmayonlycoveronefloorofanofficebuilding,buteliminatesinstallationofdedicatednetworkcabling. Ultra-High-frequencycommunication(≥100MHz) ThehighestinformationratetransmissionsoverpowerlineuseRFthroughmicrowavefrequenciestransmittedviaatransversemodesurfacewavepropagationmechanismthatrequiresonlyasingleconductor(USpatent7,567,154 ).AnimplementationofthistechnologycalledE-Linehasbeendemonstratedusingasinglepowerlineconductor.Thesesystemshavedemonstratedsymmetricandfullduplexcommunicationwellinexcessof1Gbit/sineachdirection.MultipleWiFichannelswithsimultaneousanalogtelevisioninthe2.4and5.3GHzunlicensedbandshavebeendemonstratedoperatingoverasinglemediumvoltagelineconductor.Becausetheunderlyingpropagationmodeisextremelybroadband,itcanoperateanywhereinthe20 MHz-20 GHzregion.Alsosinceitisnotrestrictedto<80MHz,asisthecaseforhigh-frequencyBPL,thesesystemscanavoidtheneedtosharespectrumwithotherlicensedorunlicensedservicesandcancompletelyavoidtheinterferenceissuesassociatedwithuseofsharedspectrumwhileofferingcompleteflexibilityformodulationandprotocolsofaRF-microwavesystem. Highfrequencycommunicationmay(re)uselargeportionsoftheradiospectrumforcommunication,ormayuseselect(narrow)band(s),dependingonthetechnology Homenetworking(LAN) ALANisasystemofcomputersandassociatedperipheralssuchasPrintersthatarephysicallyconnectedbycablewithinalimitedgeographicalarea-typicallyinanofficebuildingoronacollegecampus.Thetopologyofthenetworkmaybering,starorbus.LANsusefiberopticsorcoaxialcabletoconnectcomputers,andeachcomputermusthavespecialcommunicationssoftwareinstalledoilitsharddisk.SoftwarehasbeendevelopedthatallowscomputerswithdifferentplatformstocoexistandexchangedataonthesameLAN. Powerlinecommunicationscanalsobeusedinahometointerconnecthomecomputers(andnetworkedperipherals),aswellasanyhomeentertainmentdevices(includingTVs,Blu-rayplayers,gameconsolesandInternetvideoboxessuchasAppleTV,Roku,KodakTheatre,etc.)thathaveanEthernetport.Consumerscanbuypowerlineadaptersetsatmostelectronicsretailersandusethosetoestablishawiredconnectionusingtheexistingelectricalwiringinthehome.Thepowerlineadaptersplugintoawalloutlet(orintoanextensioncordorpowerstrip,butnotintoanyunitwithsurgesuppressionandfiltering,asthismaydefeatthesignal)andthenareconnectedviaCAT5tothehome’srouter.Then,asecond(orthird,fourth,fifth)adapter(s)canbepluggedinatanyotheroutlettogiveinstantnetworkingandInternetaccesstoanEthernet-equippedBlu-rayplayer,agameconsole(PS3,Xbox360,etc.)alaptoporanInternetTV(alsocalledOTTforOver-the-Topvideo)boxthatcanaccessandstreamvideocontenttotheTV. ThemostestablishedandwidelydeployedpowerlinenetworkingstandardforthesepowerlineadapterproductsisfromtheHomePlugPowerlineAlliance.HomePlugAVisthemostcurrentoftheHomePlugspecifications(HomePlug1.0,HomePlugAVandthenewHomePlugGreenPHYforsmartgridcomprisethesetofpublishedspecifications)andithasbeenadoptedbytheIEEEP1901groupasabaselinetechnologyfortheirstandard,duetobepublishedandratifiedinSeptemberorOctoberof2010.HomePlugestimatesthatover45millionHomePlugdeviceshavebeendeployedworldwide.OthercompaniesandorganizationsbackdifferentspecificationsforpowerlinehomenetworkingandtheseincludetheUniversalPowerlineAssociation,theHD-PLCAllianceandtheITU-T’sG.hnspecification. Internetaccess(broadbandoverpowerlines) Broadbandoverpowerlines(BPL),alsoknownaspower-lineInternetorpowerband,istheuseofPLCtechnologytoprovidebroadbandInternetaccessthroughordinarypowerlines.Acomputer(oranyotherdevice)wouldneedonlytoplugaBPL"modem"intoanyoutletinanequippedbuildingtohavehigh-speedInternetaccess.InternationalBroadbandElectricCommunicationsorIBECandothercompaniescurrentlyofferBPLservicetoseveralelectriccooperatives. BPLmayof
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