According to physics.org
With the arrival of the mobile phone in the 1980s, communications were no longer tethered to homes, offices or payphones. But the really clever invention wasn’t the phone itself but the cellular network that supported it.
How do mobile phones work?
Imagine calling a friend on the other side of town. As you chat away, your phone converts your voice into an electrical signal, which is then transmitted as radio waves and converted back into sound by your friend’s phone. A basic mobile phone is therefore little more than a combined radio transmitter and a radio receiver, quite similar to a walkie-talkie or CB radio.
In order to remain portable, mobile phones need to have relatively compact antennas and use a small amount of power. This means that mobile phones can send a signal over only a very short range, just like a walkie-talkie.
The cellular network, however, enables you to spread the latest gossip regardless of how far away your friends are. This is done by dividing up land into a patchwork of ‘cells’ – hexagonal areas of land each equipped with their own phone mast (also called a base station).
These huge phone masts pick up the weak signal from your phone and relay it onwards to another phone mast nearer to your friend. And if you’re on the move while you talk, your phone switches masts as you go without interrupting your call.
Staying in touch
Cells also solve another conundrum – there are a limited number of radio frequencies available to mobile phone networks (typically about 800). Furthermore, a mobile phone conversation requires one frequency for speaking (transmitting) and one for listening (receiving). As a consequence, just 400 conversations could use up all the available bandwidth.
But using cells means that the same frequencies can be re-used by each cell. In busy areas such as city centres, a denser network of phone masts and smaller cells ensure there are enough frequencies for everyone. It’s therefore rare for available frequencies to run out, except at really hectic times like midnight on New Year’s Eve