Since the GSM network standard was first released, the total number of carrier frequency ranges that GSM networks are deployed has expanded today. Although most 2G GSM networks operate in the 900 or 1800 MHz frequency bands, the 850 and 1900 MHz bands are used when the 900 or 1800 MHz frequency bands are already allocated to other use such as in the United States and Canada. In some countries, the 400 and 450 MHz frequency bands are used since they were previously allocated for 1G cellular systems. As a comparison, the majority of 3G networks deployed in Europe are designed to operate in the 2100 MHz frequency band.
No matter what frequency is being used by the GSM network operator, the active one is divided into timeslots for individual cell phone use. As a result, 16 half-rate speech channels or eight full-rate can be used per radio frequency. These timeslots are then collected within a single TDMA frame and the channel data rate for eight channels is 270.833 kbit/second with a frame duration of 4.615 ms. The GSM standard also limits the transmission power out of a handset to 2 watts for GSM frequency bands 850 and 900 MHz and one watt in the 1800 or 1900 MHz bands.