GSM(Global System for Mobile Communication)
The success of mobile systems across the worid is a sign that communication is moving
towards a amore personalized,convenient system.People who have to use a mobile phone on
business soon begin to realize that the ability to phone any time,any place in one's
personal life rapidly becomes a necessity,not a convenience.
The speed and rapidity with which the personal communications revolution takes place
is,unlike fixed transmission systems,highly dependent on technology and communication
standards.
For mobile the three key elements to achieving service take-up are the cost,the size and the
weight of the phone,and the cost and quality of the link.If any of these are
wrong,especially the first two,then market growth is liable to be severely restricted.
The fixed telephone service is global and the interconnection varies from coaxial cable to
optical fiber and satellite.The national standards are different,but with common interfaces
and interface conversion,interconnection can take place.For mobile the problem is far more
complex,with the need to roam creating a need for complex networks and systems.Thus in
mobile the question of standards is far more crucial to success than fixed systems.In
addition,there is also the vexed question of spectrum allocation in the mobile area.
Mobile systems originally operated in analogue mode(and still do) in the 450 MHz band,moving
later to 900 MHz with digital GSM and then to 1800 MHz with personal communications systems.
The history of mobility can split into generations.The first generation systems were the
advanced mobile phone systems(AMPS) in the US,total access communication systems(Tacs) in
most of Europe and Nordic mobile telephone system(NMTS);which were all analogue systems.The
second generation is very much dominated by the standard first set out in Europe by the
group special mobile (GSM) committee,which was designed as a global mobile communication
system.
不要用那種在線翻譯的來糊弄過去,那種看得出來.