Wireless World
GSM (Global System for Mobile communication)
GSM (Global System for Mobile communication) is a digital mobile
telephony system that is widely used in Europe and other parts of the
world. GSM uses a variation of time division multiple access (TDMA) and is the most widely used of the three digital wireless telephony technologies (TDMA, GSM, and CDMA).
GSM digitizes and compresses data, then sends it down a channel with
two other streams of user data, each in its own time slot. It operates
at either the 900 MHz or 1800 MHz frequency band.Where these bands were already allocated, the 850 MHz and 1900 MHz bands
were used instead (for example in Canada and the United States). In
rare cases the 400 and 450 MHz frequency bands are assigned in some
countries because they were previously used for first-generation
systems.The transmission power in the handset is limited to a maximum of 2 watts in GSM 850/900 and 1 watt in GSM 1800/1900.
