GSM -全球移动通信系统

中文字数:4967,中文页数:6   英文字数: 2855,页数:6

GSM -全球移动通信系统
概述:
    GSM （全球移动通信系统） 是一种欧洲数字通信标准。它为具有承载GSM能力的设备提供了全双工通信方式。 例如一个电话，传真或传呼机，利用TDMA通信方案传送数据时可以达到9600bps。由于GSM是完全数字化的，它可以很容易接入其他数字通信系统，如综合业务数字网.它还可以接入数字设备，如第3组传真机。如手机一类的GSM产品不同于其它任何服务的地方就是它需要使用一个用户识别模块或SIM卡。这些小型电子设备大约有大小如一张信用卡，并记录了所有的用户信息。这些数据包括程控电话号码和用来识别用户的网络安全特点. 如果没有这个模块，该设备将无法运作。这张卡大大提升了使用的安全性能。同时这张卡易于使用，因为它可以用于不同的手机，并能保存用户的有用信息。GSM在欧洲以外还以不同的名称为人所知。在北美洲它被称为PCS1900。在其他的地方又被称为DCS1800(同时又被称为PCS)。 唯一的区别是这些系统运行于不同的频率。名称中的数字代表了系统运行于什么频段。虽然每个系统所使用的GSM标准的，他们不是彼此兼容。
技术:
GSM提供的服务

 GSM - Global System for Mobile Communications

Overview
 GSM (Global System for Mobile Communications) is a European digital communications standard which provides full duplex data traffic to any device fitted with GSM capability, such as a phone, fax, or pager, at a rate of 9600 bps using the TDMA communications scheme. Since GSM is purely digital, it can easily interface with other digital communications systems, such as ISDN, and digital devices, such as Group 3 facsimile machines. Unlike any other service, GSM products such as cellular phones, require the use of a Subscriber Identity Module, or SIM card. These small electronic devices are approximately the size of a credit card and record all of the user information of it. This includes data such as programmed telephone numbers and network security features which identify the user. Without this module, the device will not function. This allows for greater security and also greater ease of use as this card may be transported from one phone to another, while maintaining the same information available to the user. GSM is also present outside of Europe but known by different names. In North America it is known as PCS 1900 and elsewhere are DCS 1800 (also known as PCS). The only difference between these systems is the frequency at which operate. The number stands for the operating frequency in megahertz. While each system uses the GSM standard, they are not compatible with each other.
Technology
Services provided by GSM

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