Basic Knowledge About Telecommunication
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GSM (Global System for Mobile communication)



.The first generation of cellular phone was analog, but the current generation is digital, using packet radio. Digital transmission has several advantages over analog for mobile communication.
1- Voice, data and fax can be integrated into a single system.
2- As better speech compression algorithms are discovered, less bandwidth will be needed per channel.
3- Error-correction codes can be used to improve transmission quality.
4- Digital signals can be encrypted for security.


.Although it might be nice if the whole world had adopted the same digital standards, such is not the case. The U.S. system, IS-54, and the Japanese system, JDC, have been designed to be compatible with each country’s existing analog system.
.In contrast, the European digital system. GSM (Global System for Mobile communication), has been designed from scratch as a fully digital system, without any compromises for the sake of backward compatibility (e.g., having to use the existing frequency slots).