How Do Cell
Phones Work?
It’s amazing. An instrument that can be held
in the palm of your hand enables you to talk to friends and
family around the world. How is this possible?
A Radio
The cell phone is essentially a radio. Before the cell phone as
we know it was invented, police officers used radio technology
to communicate. This consisted of a large tower that covered a
wide area. If the officer was within that area, he could
communicate via the radio with other officers, if he was
outside of the range of that tower, he would not be able to
communicate. There were also a limited number of channels
available for communication. Cell phone technology breaks a
city into small cells. Instead of a high power transmission
tower, a low power transmission tower is located within each
cell, this allows for frequency reuse so that many people can
use the same frequency allowing a larger number of people to be
on the cell phone at one time without overloading the airwaves.
Another difference between a cell phone and the first car
phones is that a cell phone is considered a full-duplex device,
meaning that a person talks on one frequency and listens on
another. This was an important development that allowed both
people to talk at once, unlike a walkie-talkie.
Low Power Transmission
Both the base station and the cell phone have lower power
transmission. This is important because it allows other base
stations, which are more than 10 miles away, to reuse the same
frequency without interrupting calls. This provides more
channels through which a cell phone call can travel, unlike a
CB radio, which has far fewer channels. Low power transmission
also means that cell phones are smaller because they take less
battery power to operate. Both of these qualities are keys to
the cell phone’s success.
Digital Technology
The introduction of digital technology allows the speaker’s
voice to be compressed into binary numbers. This compression
method means that at any time, between three and ten cell
phones can occupy the same amount of space as one analog
call.
2G Technology
Second generation (2G) technology is composed of three
technologies for transmitting information. The first is
Frequency Division Multiple Access (FDMA) which places each
call on a separate frequency. FDMA was used mainly in analog
technology; it is not very effective for digital technology.
The second is Time Division Multiple Access (TDMA) which allots
a certain amount of time to each frequency. And the third is
Code Division Multiple Access (CDMA), which gives a specific
code to each call.
3G Technology
Third
generation (3G) technology adds Internet and e-mail abilities
to cell phones. 3G phones, which are also called smartphones,
feature extra bandwidth and transfer rates in order to allow
the Web applications and phone-based audio and visual files. 3G
networks are able to transfer at speeds of up to 3 Mbps. These
phones are like pocket-sized laptops that allow the user to
carry a virtual computer in his pocket.
Cell Phone Towers
Without cell phone towers, none of these technologies would be
carried from phone to phone. Cell phone towers are placed
throughout cities and the countryside. Without these towers,
cell phones would be unable to pick up a signal. Often, each
tower has multiple providers who have access to it. This means
that there are fewer towers put up as providers pay fees to
share one tower. Some towers are even disguised as tall trees
in order to blend in to the countryside and create visual
appeal.
Today’s cell phone is one of the most
complicated technological instruments that we carry with us. It
is amazing how far the technology has come in just 30 years,
and it’s mind blowing to think of the advances that may be made
in the next 30 years.
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