Editing GSM (section)

==== GSM carrier frequencies ====
{{Main|GSM frequency bands}}
GSM networks operate in a number of different [[carrier frequency]] ranges (separated into [[GSM frequency ranges]] for 2G and [[UMTS frequency bands]] for 3G), with most [[2G]] GSM networks operating in the 900&nbsp;MHz or 1800&nbsp;MHz bands. Where these bands were already allocated, the 850&nbsp;MHz and 1900&nbsp;MHz bands were used instead (for example in Canada and the United States). In rare cases the 400 and 450&nbsp;MHz frequency bands are assigned in some countries because they were previously used for first-generation systems.

For comparison, most [[3G]] networks in Europe operate in the 2100&nbsp;MHz frequency band. For more information on worldwide GSM frequency usage, see [[GSM frequency bands]].

Regardless of the frequency selected by an operator, it is divided into [[time-division multiplexing|timeslots]] for individual phones. This allows eight full-rate or sixteen half-rate speech channels per [[radio frequency]]. These eight radio timeslots (or [[burst transmission|burst]] periods) are grouped into a [[Time-division multiple access|TDMA]] frame. Half-rate channels use alternate frames in the same timeslot. The channel data rate for all {{nowrap|8 channels}} is {{nowrap|270.833&nbsp;kbit/s,}} and the frame duration is {{nowrap|4.615 ms.}}<ref>{{Cite web |title=GSM Frame Structure: Multiframe Superframe Hyperframe » Electronics Notes |url=https://www.electronics-notes.com/articles/connectivity/2g-gsm/frame-structure-superframe-hyperframe-multiframe.php |access-date=2023-02-09 |website=www.electronics-notes.com}}</ref> TDMA noise is interference that can be heard on speakers near a GSM phone using TDMA, audible as a buzzing sound.<ref>{{Cite web |date=May 2013 |title=AN-1496 Noise, TDMA Noise, and Suppression Techniques |url=https://www.ti.com/lit/an/snaa033d/snaa033d.pdf |website=Texas Instruments |series=Application Report SNAA033D |edition=Revised}}</ref>
 
The transmission power in the handset is limited to a maximum of 2 watts in {{nowrap|GSM 850/900}} and {{nowrap|1 watt}} in {{nowrap|GSM 1800/1900}}.