Different mobile systems have been developed such as GSM, NA-TDMA, CDMA, PDC etc… The analog cellular systems can only use the FDMA (Frequency Division Multiple Access) but the digital cellular systems can use the Time Division Multiple Access(TDMA) or the Code Division Multiple Access(CDMA). The long form of GSM is global system for mobile communications and it uses TDMA. We know that in TDMA each user is allowed to use the radio channel for a fixed duration of time. During this time slot, the user is allowed to make full use of the channel. Hence the data are transmitted in the form of bursts.
An European group called CEPT started the development of GSM TDMA system in 1982. The first GSM was implemented in Germany in 1992. It was named as D2.