?計算機英語?課件Chapter8CommunicationSystem-副本Chapter8CommunicationSystemObjectiveAfterreadingthischapter,youshouldbeableto:Definethetermofcommunicationsystem.Givesomeexamplesofcommunicationmediaandconnectiondevices.Graspsomeknowledgeaboutpopularnewcommunicationtechnologies.Definethetermofdatatransmissionandknowfactorsofdatatransmission.8.2CommunicationMediaThecommunicationmediaincludestwistedpaircables,coaxialcables,fibercables,radiowaves,infraredtransmissions,microwaves,andcommunicationsatellites.8.2CommunicationMedia1.TwistedpairCable8.2CommunicationMedia2.CoaxialCables8.2CommunicationMedia3.FiberCables8.2CommunicationMedia4.RadioWave6.Microwave5.Infraredtransmission8.2CommunicationMedia7.CommunicationSatellites8.3ConnectionDevicesConnectionDevicesarehardwarecomponentsusedtoconnectvariouspartsofanetwork.8.4CommunicationTechnologyCommunicationTechnologyisbasicallytheuseoftechnologiestocommunicatewithotherpeople,thus,everythingfromthepostalservicetowirelessphonesandInternet.Therearesomepopulardatacommunicationnewtechnologies,suchasISDN,ADSL,GSM,Bluetooth,andCDMA.8.4CommunicationTechnology1.ISDN

Abbreviationofintegratedservicesdigitalnetwork,itisaninternationalcommunicationsstandardforsendingvoice,video,anddataoverdigitaltelephonelinesornormaltelephonewires.

8.4CommunicationTechnology2.ADSL

Shortforasymmetricdigitalsubscriberline,itisanewtechnologythatallowsmoredatatobesentoverexistingcoppertelephonelines(POTS).ProvidersusuallymarketADSLasaserviceforconsumerstoconnecttotheInternetinarelativelypassivemode:abletousethehigherspeeddirectionforthe"download"fromtheInternetbutnotneedingtorunserversthatwouldrequirehighspeedintheotherdirection.8.4CommunicationTechnology3.GSM

ShortforGlobalSystemforMobileCommunications,itisoneoftheleadingdigitalcellularsystems.8.4CommunicationTechnology4.Bluetooth

Bluetooth

isanopenwirelessprotocolforexchangingdataovershortdistancesfromfixedandmobiledevices,creatingpersonalareanetworks(PANs).ItaimedatsimplifyingcommunicationsamongInternetdevicesandbetweendevicesandtheInternet.

8.4CommunicationTechnology4.Bluetooth8.4CommunicationTechnology5.CDMAShortforCode-DivisionMultipleAccess,itisadigitalcellulartechnologythatusesspread-spectrumtechniques.

8.4CommunicationTechnology6.UWBShortforUltrawideband,itisaimedathighdataratesforpersonalareanetworks,whichhaveaneffectiveoperatingradiusofapproximately10metersorless.ThoughsimilartothecurrentcapabilitiesofBluetooth,itusesaverydifferenttechnology.8.5DataTransmissionDatatransmissionisthetransferofdataorinformationbetweenasourceandareceiver.Severalfactorsaffecthowdataistransmitted.Theyincludebandwidth,serial

or

parallel

transmission,direction

ofdataflow,andprotocols.8.5DataTransmission1.Bandwidth

Bandwidthisameasurementofthecapacityofthecommunicationchannel.2.SerialorParallelTransmission

Datatravelsintwoways:seriallyandinparallel.

8.5DataTransmission2.SerialorParallelTransmission8.5DataTransmission3.DirectionofDataFlow8.5DataTransmission4.ProtocolsIncomputing,aprotocolisaconventionorstandardthatcontrolsorena