GSM(GlobalSystemforMobileCommunication)Thesuccessofmobilesystemsacrosstheworidisasignthatcommunicationismovingtowardsaamorepersonalized,convenientsystem.Peoplewhohavetouseamobilephoneonbusinesssoonbegintorealizeth

　　GSM(GlobalSystemforMobileCommunication)

　　Thesuccessofmobilesystemsacrosstheworidisasignthatcommunicationismoving

　　towardsaamorepersonalized,convenientsystem.Peoplewhohavetouseamobilephoneon

　　businesssoonbegintorealizethattheabilitytophoneanytime,anyplaceinone's

　　personalliferapidlybecomesanecessity,notaconvenience.

　　Thespeedandrapiditywithwhichthepersonalcommunicationsrevolutiontakesplace

　　is,unlikefixedtransmissionsystems,highlydependentontechnologyandcommunication

　　standards.

　　Formobilethethreekeyelementstoachievingservicetake-uparethecost,thesizeandthe

　　weightofthephone,andthecostandqualityofthelink.Ifanyoftheseare

　　wrong,especiallythefirsttwo,thenmarketgrowthisliabletobeseverelyrestricted.

　　Thefixedtelephoneserviceisglobalandtheinterconnectionvariesfromcoaxialcableto

　　opticalfiberandsatellite.Thenationalstandardsaredifferent,butwithcommoninterfaces

　　andinterfaceconversion,interconnectioncantakeplace.Formobiletheproblemisfarmore

　　complex,withtheneedtoroamcreatinganeedforcomplexnetworksandsystems.Thusin

　　mobilethequestionofstandardsisfarmorecrucialtosuccessthanfixedsystems.In

　　addition,thereisalsothevexedquestionofspectrumallocationinthemobilearea.

　　Mobilesystemsoriginallyoperatedinanaloguemode(andstilldo)inthe450MHzband,moving

　　laterto900MHzwithdigitalGSMandthento1800MHzwithpersonalcommunicationssystems.

　　Thehistoryofmobilitycansplitintogenerations.Thefirstgenerationsystemswerethe

　　advancedmobilephonesystems(AMPS)intheUS,totalaccesscommunicationsystems(Tacs)in

　　mostofEuropeandNordicmobiletelephonesystem(NMTS);whichwereallanaloguesystems.The

　　secondgenerationisverymuchdominatedbythestandardfirstsetoutinEuropebythe

　　groupspecialmobile(GSM)committee,whichwasdesignedasaglobalmobilecommunication

　　system.

　　不要用那种在线翻译的来糊弄过去,那种看得出来.