GSM(Global System for Mobile Communication)

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.
不要用那种在线翻译的来糊弄过去,那种看得出来.

移动系统在全球范围的成功标志着通讯系统正在朝着更加个人化更加便利的方向发展.不得不使用移动电话的商务人士们不久就开始意识到,这种在个人生活中何时何地都能打电话的状况已经变成了一种必要,而不是便利.
个人通讯革命的高速发展不像固定传输系统那样,高度取决于技术和通讯标准.
对于移动电话,取得服务权的三个要素是：价格,机子的大小重量,还有连接的成本和质量.如果任何一个要素出错了,特别是前两个,那么市场增长率就很严酷地受限了.
固定电话服务是全球化的,通过多种渠道有同轴电缆,光纤,还有卫星等来互相连通.国家标准不同,但是通过共同的界面以及不同界面间的转换,也可以达到互相连接.而对于移动电话来说,这个问题要更加复杂,因为漫游需要更复杂的网络和体系.因此,对于移动电话,标准的问题对于成功比起固定电话来更加至关重要.另外,在移动领域还有一个难题就是频段的分配.
移动电话体系最初是在对等模式运营的（现在也是）在450兆赫兹波段,后来变成了数字GSM的900兆赫兹,后来又变成了个人通讯系统的1800兆赫兹.
移动电话的历史可以被分成几代.第一代是美国高级移动电话系统（AMPS）,欧洲大部分地区的全数据通讯系统（Tacs）以及北欧移动电话系统.这些都是对等系统.
第二代被由欧洲开始的标准统治的群组特别移动委员会（GSM）,被设计成一个全球移动通讯系统.