How Do Mobile Phones Work?
Mobile phones have become a ubiquitous part of our lives. However, you may not be aware of just how mobile phones work.
It might surprise you to learn that a mobile phone is essentially a
radio. In fact, the Citizens' Band radio of the 1970s and early 1980s
was a primitive form of this technology. These early communication
systems required large and heavy radio transmitters, and so were used
primarily by truckers, who could handle the extra weight. They used one
central antenna tower per major city, with a few dozen channels or
frequencies available to each tower. Because of this, the system
wouldn't work if there were too many people trying to use it. Calls
could not be made across distances greater than the local tower could
reach. Additionally, the system was only "half-duplex," so only one
party could talk at any given time, leading to the unique CB radio
lingo.
At heart, mobile phones use the same basic radio transmission technique
as those old radio systems. But instead of communicating with a single
radio tower, modern mobile phones use cellular networks. Cellular
networks are a sophisticated form of radio network based, fittingly
enough, on the concept of the cell. A cell is a distributed portion of
land, usually hexagon-shaped, though squares and circles have also been
used. Each cell is occupied by at least one radio tower. Each cell is
also assigned a variety of frequencies which correspond to radio base
stations. Adjacent cells are not allowed to use the same frequencies;
they need to be spaced at least one cell apart to avoid interference.
Because of this setup, cellular networks can use the same frequency in
multiple areas for different transmissions. They can also transmit calls
from one tower to another, allowing the calls to reach across
continents if need be.
Mobile phone networks have become more sophisticated over the years.
They around 800 different frequencies, and calls can change frequency
under the guidance of automated computer systems that find the optimal
ranges to avoid interference. Truly, mobile phones are a marvel of
modern ingenuity.
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