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.