通信工程师考试复习题高级英语试卷

通信英语强化训练试题（四单项选择题：(Choosethebest( theproblemisfarmorecomplex,withtheneedtoroam needforcomplexnetworksandsystems.Thus thequestionofisfarmorecrucialtosuccess fixedA.tocreate, B.creating,C.creation, D.created,(The networks, indenselypopulatedareas,could byaverysmallnumberofsimultaneousA.operation, B.operate,C.operating, D.tooperate,to(TheuseofdigitalradiotransmissionandtheadvancedhandoverbetweenradiocellsinGSMnetworksallowsforbetterfrequency oguecellularsystems,thus thenumberofthatcanbeA.that, B.which,C.the,to D.than,( intended isdeveloped, B.bedeveloped,C.todevelop, D.beingdeveloped,to Theswitch, circuitswitches,havenocapabilityof dataontheirwaytothedestination.A.calling, B.called,C.tocall,to D.becalled,be(Thecircuitissetupbyaspecialsignalingmessage findsitsthroughthenetwork, channelsinthepathasitA.that, B.where,C.who, D.one,be(Theswitchingelementisacomputer amessageprocessor,processingandstoragecapabilities.Messagetravelsindependentlyandasynchronously, theirownwayfromsourcetodestination.A.tocall, B.calling,C.referredtoas, D.becalled, Avariationofmessageswitchingispacketswitching.Herethemessage A.given, B.give,C.giving, D.togive,to

ATMtransfersinformation shortpacketscalled"cells" fixedlengthof48bytesplusfiveheadsbytes.A.of, B.in,C.to, D.for, ATMretainsalltheflexibilityofpacketmode,information

onlyA.enable, B.enabling,tobeC.enabled,to D.toenable,be ATM, thanany municationstechnique,is thecurrentandfuturerequirementsofbothoperatorsandA.greater, B.many,toC.much, D.muchmore,to()12. ATMwasinitiallyintended highbitrates,butithasinfactprovedtobeauniversaltechniquefor anytypeofdigitizedinformationatawidevarietyofbitrates.A.handle, B.handling,toC.handled, D.tohandle,()13. Ontheotherhand,ATMretainsalltheflexibilityofpacketmode, requiredinformation A.enabling,tobe B.enable,beC.toenable,to D.enabled,()14. ATMdatedfromthebeginningofthe1980s:atthetime,people tofindthemostsuitabletechnique highbitratechannelatmorethanMA.istrying, B.weretrying,C.aretrying,to D.wanttotry,to短语英译汉：(Translatethefollowingphrasesintototalaccesscommunication communicationtimedivisionmultiple andshortmessagefixedcommunicationa alizedthecostandqualityofthemarket ephonecoaxialinterfacecellularcommunicationfrequencyreuseandcellcochanneltheoreticalspectralmicro-cellularbasestationsubscriberbursttransmissionoverheadadvancedhandovertheGSMtechnicalthecapabilityofstoringormanipulatinguser'sthespecialsignalingawelldefinedblockofdatacalledatheinformationregardingthesourceanddestinationthecomputerreferredtoasamessagethestore-and-forwardtransmissionthedynamicallocationofthetheoveralltransmissiondelayoftheswitchingcircuitmessagepackettotalpathofconnectedsource-destinationcommunicationtransmissioninitialconnectioncostincurredinsettingupthelowdelayconstraintrequiredbythethefixeddedicatedend-to-endlowchannelshortpacketscalledbitratesofseveralhundredmegabitsauniquemultiplexingthephysicalconnectionbetweenanytwo anaturevehicleformultimediathecurrentandfuturerequirementsofbothoperatorsandthetechniqueforswitchinghighbitrateasynchronoustransfermultiplexingandswitchingtheunderlyingtypeofdualvirtualvirtualthetransferofcellstothenetworkhundredsmegabitsamendationthequalityofinproportiontotheexacttheapplicationsandservicestransportedoveratheabilitytoconstructvirtualcost-effectiveuseofcoordinatingdifferentnetworkscarryingdifferentessentialcomponentsoffutureinformationstatisticaloptimumuseofvirtualprivate短语汉译英：(Translatethefollowingphrasesinto固 业

ATM虚拟：(ranslate Thesuccessofsystemsacrosstheworldisasignthatcommunicationismovingtowardsamore alized,convenientsystem.Peoplewhohavetouseaphoneonbusinesssoonbegintorealizethattheabilitytophoneanytime,anyceinone's allife esanecessity,notaconvenience.Thefixedephoneserviceisglobalandtheinterconnectionvariesfromcoaxialcabletoopticalfiberandsalite.Thenationalstandardsaredifferent,butwithcommoninterfacesandinterfaceconversion,interconnectioncantakece.Fortheproblemisfarmorecomplex,withtheneedtoroamcreatinganeedforcomplexnetworksandsystems.Thusinthequestionofstandardsisfarmorecrucialtosuccessthanfixedsystems.TheGSMsystemisbasedonacellularcommunicationsprinciplewhichwasfirstproposedasaconceptinthe1940sbyBellSystemengineersintheUS.Theideacameoutoftheneedtoincreasenetworkcapacityandgotroundthefactthatbroadcast operatingindenselypopulatedareas,couldbejammedbyaverysmallnumberofsimultaneouscalls.Thepowerofthecellularsystemwasthatitallowedfrequencyreuse.Thecellularconceptisdefinedbytwofeatures,frequencyreuseandcellsplitting.Frequencyreusecomesintoybyusingradiochannelsonthesamefrequencyincoverageareasthatarefarenoughapartnottocausecochannelinterference.Thisallowshandlingofsimultaneouscallsthatexceedthetheoreticalspectralcapacity.Cellsplittingisnecessarywhenthetrafficdemandonacellhasreachedthe umandthecellisthenderivedintoamicro-cellularsystem.Thecellcoverageareaiscontrolledbyabasestationwhichisitselfmadeupof.twoelements.Thefirstelementisthetransmissionsystemwhichcommunicatesouttotheandalsoreceivesinformationfromittosetupandmaintaincallswhenactuallyinoperation.Thebasestationtransceiveriscontrolledbythebasestationcontroller,whichcommunicateswiththeswitchingcenter-theessentiallinktothelocalpublicswitchedephonenetwork,andtothesubscriberdatawhichisstoredinregisterswithinthesystem.TheGSMsystemoperatesinabursttransmissionmodewith124radiochannelsinthe900kbit/s,6kbit/sor12.6kbit/s.Thesetwoformsofinformationaretheusefulpartofthetransmission,TheuseofdigitalradiotransmissionandtheadvancedhandoveralgorithmsbetweenradiocellsinGSMnetworksallowsforsignificantlybetterfrequentlyusagethaninoguecellularsystems,thusincreasingthenumberofsubscribersthatcanbeserved.SinceGSMprovidescommonstandard,cellularsubscriberswillalsobeabletousetheirephonesovertheentireGSMservicearea.RoamingisfullyautomaticbetweenandwithinallcountriescoveredbyGSMInadditiontointernationalroaming,GSMprovidesnewuserservices,suchashighspeeddatacommunication,facsiandshortmessageservice.TheGSMtechnicalspecificationsaredesignedtoworkinconcertwithotherstandards,e.g.ISDN.Interworkingbetweenthestandardsisinthiswayassured.Inthelongtermcellularsystems,usingadigitaltechnology, etheuniversalmethodof Incircuitswitching,atotalpathofconnectedlinesissetupfromtheorigintothedestinationatthetimethecallismade,andthepathremainsallocatedtothesource-destinationpair(whetherusedornot)untilitisreleasedbythecommunicatingparties.Theswitches,calledcircuitswitches,havenocapabilityofstoringormanipulatinguser'sdataontheirwaytothedestination.Thecircuitissetupbyaspecialsignalingmessagethatfindsitswaythroughthenetwork,seizingchannelsinthepathasitproceeds.Oncethepathisestablished,areturnsignalinformsthesourcetobegintransmission.containsinformationregardingthesourceanddestinationaddressesaswellasothercontrolMessagestravelindependentlyandasynchronously,findingtheirownwayfromsourcetodestination.Firstthemessageistransmittedfromthehosttothemessageprocessortowhichitisattached.Oncethemessageisentirelyreceived,themessageprocessorexaminesitsheader,andaccordinglydecidesonthenextoutgoingchannelonwhichtotransmitit.Ifthisselectedchannelisbusy,themessagewaitsinaqueueuntilthechannel es,atwhichtimetransmissionbegins.Avariationofmessageswitchingispacketswitching.Herethemessageisbrokenupintoseveralpiecesofagiven umlength,calledpackets.Aswithmessageswitching,eachpacketcontainsaheaderandachecksum.Packetsaretransmittedindependentlyinastore-and-forwardmannerandpacketswitchingachievesthebenefitsprovidedbymessageswitchingandoffersaddedfeatures.Withcircuitswitching,thereisalwaysaninitialconnectioncostincurredinsettingupthecircuit.Itiscost-effectiveonlyinthosesituationswhereoncethecircuitissetupthereisaguaranteedsteadyflowofinformationtransfertoamortizetheinitialcost.Thisiscertainlythecasewithvoicecommunicationinthetraditionalway,andindeedcircuitswitchingisthetechniqueusedintheephonesystem.Communicationamongcomputers,however,ischaracterizedasbusty.Burstinessisaresultofthehighdegreeofrandomnessencounteredinthemessage-generationprocessandthemessagesize,andofthelowdelayconstraintrequiredbytheuser.Theusersanddevicesrequirethecommunicationresourcesrelativelyinfrequently;butwhentheydo,theyrequirearelativelyrapidresponse.Therefore,forburstyusers,store-and-forwardtransmissiontechniquesofferamorecost-effectivesolution,sinceamessageoccupiesaparticularcommunicationslinkonlyforthedurationofitstransmissiononthatlink;therestofthetimeitisstoredatsomeintermediatemessageswitchandthelinkisavailableforothertransmissions.Thusthemainadvantageofstore-and-forwardtransmissionovercircuitswitchingisthatthecommunicationbandwidthisdynamicallyallocated,andtheallocationisdoneonthefinebasisofaparticularlinkinthenetworkandaparticularmessage.Packetswitchingachievesthebenefitsdiscussedsofarandoffersaddedfeatures.Itprovidesthefulladvantageofthedynamicallocationofthebandwidth,evenwhenmessagesarelong.Indeed,withpacketswitching,manypacketsofthesamemessagemaybeintransmissionsimultaneouslyoverconsecutivelinksofapathfromsourcetodestination,thusachievinga"pipelining"effectsandreducingconsiderablytheoveralltransmissiondelayofthemessageascomparedtomessageswitching.requiresmallerstorageallocationattheintermediateswitches.Italsohasbettererrorcharacteristicsandleadstomoreefficienterrorrecoveryprocedures,asitdealswithsmallerentities.Needlesstosay,packetswitchingpresentsdesignproblemsofitsown,suchastheneedtoreorderpacketsofagivenmessagethatmayarriveatthedestinationnodeoutofsequence.AsynchronousTransferMode(ATM)isbothamultiplexingandswitchingtechnique.Itwasinitiallyintendedtohandlehighbitrates,butithasinfactprovedtobeauniversaltechniquefortransportingandswitchinganytypeofdigitizedinformationatawidevarietyofbitrates.Today,theworldof municationshaspaidgreatattentiontotheATM'sdevelopments.ATMtransfersinformationinshortpacketscalled"cells"withafixedlengthof48plusfiveheaderbytes,irrespectiveoftheunderlyingtypeoftransmission.Cellroutingisbasedontheprincipleoflogicalchannelswithdualidentification:thecellheadercontainstheidentifierofthebasicconnectiontowhichthecellbelongs-calledvirtualcircuit(VC)andtheidentifierofthegroupofVCstowhichtheconnectionbelongs-calledavirtualpath(VP).ATMisrelatedtobothcircuitandpacketmodes.Becauseofthesimplicityoftheprotocolused,thetransferofcellstonetworknodescanbehandledentirelybyhardware,whichleadstoveryshorttransittimeandhighusageoftransmissionpaths,evenatbitratesofseveralhundredmegabitsasecond.Ontheotherhand,ATMretainsalltheflexibilityofpacketmode,enablingonlyrequiredinformationtobeconveyed,offeringasimple,uniquemultiplexingmethodirrespectiveofthebitratesofthedifferentinformationflows,andallowingthesebitratestobevaried.ATMdatedfromthebeginningofthe1980s:atthetime,peopleweretryingtofindthemostsuitabletechniqueforswitchinghighbitratechannelatmorethan100Mbit/s.ThefirstATMproductsappearedonthemarketin1992:theywereforlocalareanetworksandweredesignedtosolvetheproblemsofsharingthesamebearercircuitbetweencomputerterminalsastheycontinuetoincreaseinnumbersandpower.In1988,theITU mendationI.121whichratifiedthechoiceofATMthetargettransfermodeforbroadbandnetworksforalltypesofinformation,includinglowbitrateinformationsuchasvoice.In1991severaloperatorsandmanufacturersfoundedtheATMForumtoexpeditestandardization.TheATMForumnowhasmorethan600membersandhasasignificantinfluenceonATMstandardsandspecifications.AnATMnetworkcanbeconsideredasbeingthreeoverlaidfunctionallevels.ThelevelwhichinturnmultiplexesandlogicallyroutestheinformationflowasATMcellsgothroughthetransmissionlinkssharedbylogicalconnectionscalledvirtualconnections.ThetransmissionlevelprovidesthesephysicallinksandhandlestheactualphysicaltransportoftheAnATMnetworkcantransportandswitchvoice,dataandwhich,seenfromtheaccess,usetraditionaldigitalinterfaceswiththesamequalityofservice.Thismeansthataphysicalconnectionbetweenanytwoterminalscanberecedwithanequivalentlogicalconnectionwhichismultiplexedwithothersinacommontransmissionlink.Theresourceisshareddynamicallybetweenalltheconnections.TheATMtechniquecompleyseparatestheapplicationsandservicestransportedoveranetworkfromthetransmissionresourcesused.Theabilitytoconstructvirtualnetworksmeansthatthephysicalnetworkcanbesharedbymanyusersdynamicallyandinrealtime,therebyachievingcost-effectiveuseofinfrastructure,forhighbitrateservicestoo.Investmentsatalllevelsarealsofuture-proofed,becausethedifferentapplicationscanreallocatedintimeoverthesamenetworkinfrastructureasrequirementsarise,ATMoffersauniquewayofcoordinatingdifferentnetworkscarryingdifferentservicesintoasinglephysicalATM,muchmorethananyother municationstechnique,isabletomeetthecurrentandfuturerequirementsofbothoperatorsandusers.Comparedwithothertechniquesthatmaycompeteincertainapplications,ATMisspecialmainlyduetoitsuniversalnature,bothintermsofbitrateandtypeofinformationtransferred.ATMoffersaswitchingfunctionforallbitratesandthisisparticularlysuitableforhighandvariablebitrates.阅读理解：(ChoosethebestGSM(GlobalSystemforThespeedandrapiditywithwhichthe alcommunicationsrevolutiontakesceis,unlikefixedtransmissionsystems,highlydependentontechnologyandcommunicationstandards.Forthethreekeyelementstoachievingservicetake-uparethecost,thesizeandtheweightofthephone,andthecostandqualityofthelink.Ifanyofthesearewrong,especiallyfirsttwo,thenmarketgrowthisliabletobeseverelyTheGSMsystemisbasedonacellularcommunicationsprinciplewhichwasfirstproposedasaconceptinthe1940sbyBellSystemengineersintheUS.Theideacameoutoftheneedtoincreasenetworkcapacityandgotroundthefactthatbroadcastnetworks,operatingindenselypopulatedareas,couldbejammedbyaverysmallnumberofsimultaneouscalls.Thepowero