Editing Cellular network (section)

=== Cellular frequency choice in mobile phone networks ===
{{Main|Cellular frequencies}}
The effect of frequency on cell coverage means that different frequencies serve better for different uses. Low frequencies, such as 450&nbsp; MHz NMT, serve very well for countryside coverage. [[GSM]] 900 (900&nbsp;MHz) is suitable for light urban coverage.  [[GSM]] 1800 (1.8&nbsp;GHz) starts to be limited by structural walls.  [[UMTS]], at 2.1&nbsp;GHz is quite similar in coverage to [[GSM]] 1800.

Higher frequencies are a disadvantage when it comes to coverage, but it is a decided advantage when it comes to capacity. Picocells, covering e.g. one floor of a building, become possible, and the same frequency can be used for cells which are practically neighbors.

Cell service area may also vary due to interference from transmitting systems, both within and around that cell.  This is true especially in CDMA based systems.  The receiver requires a certain [[signal-to-noise ratio]], and the transmitter should not send with too high transmission power in view to not cause interference with other transmitters. As the receiver moves away from the transmitter, the power received decreases, so the [[power control]] algorithm of the transmitter increases the power it transmits to restore the level of received power. As the interference (noise) rises above the received power from the transmitter, and the power of the transmitter cannot be increased anymore, the signal becomes corrupted and eventually unusable. In [[CDMA-based systems]], the effect of interference from other mobile transmitters in the same cell on coverage area is very marked and has a special name, ''[[cell breathing (telephony)|cell breathing]]''.

One can see examples of cell coverage by studying some of the coverage maps provided by real operators on their web sites or by looking at independently crowdsourced maps such as [[Opensignal]] or [[CellMapper]]. In certain cases they may mark the site of the transmitter; in others, it can be calculated by working out the point of strongest coverage.

A [[cellular repeater]] is used to extend cell coverage into larger areas. They range from wideband repeaters for consumer use in homes and offices to smart or digital repeaters for industrial needs.