Global System for Mobile Communications (GSM)
Global System for Mobile Communications (GSM) is mostly used second-generation technology in Europe. It is almost similar to D-AMPS. A combination o frequency-division multiplexing and time-division multiplexing are used for communication. But it provides a much better data rate than D-AMPS.
GSM uses two bands for full-duplex communication. Each band is 25 MHz wide. The forward band is from 935 MHz to 960 MHz and the reverse band is from 890 MHz to 915 Mhz. Each band consists of 124 channels and is separated by guard bands from the neighbouring bands.