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How Cell Phones Work

Date: Jan 18, 2005
Contributor: Darren Eland

Millions of people in the United States and around the world use cellular phones. They are such great gadgets -- with a cell phone, you can talk to anyone on the planet from just about anywhere!

These days, cell phones provide an incredible array of functions, and new ones are being added at a breakneck pace. Depending on the cell-phone model, you can:

Store contact information
Make task or to-do lists
Keep track of appointments and set reminders
Use the built-in calculator for simple math
Send or receive e-mail
Get information (news, entertainment, stock quotes) from the Internet
Play simple games
Integrate other devices such as PDAs, MP3 players and GPS receivers
But have you ever wondered how a cell phone works? What makes it different from a regular phone? What do all those confusing terms like PCS, GSM, CDMA and TDMA mean? In this article, we will discuss the technology behind cell phones so that you can see how amazing they really are.

If you are thinking about buying a cell phone, be sure to check out How Buying a Cell Phone Works to learn about everything you should know before making a purchase.

Let's start with the basics: In essence, a cell phone is a radio.

Most newer digital cellular phones have some sort of entertainment programs on them, ranging from simple dice-throwing games to memory and logic puzzles.

Approximately 20 percent of American teens (more girls than boys) own a cellular phone.

Cellular phones are more popular in European and Asian countries than they are in the United States -- more than 90 percent of Europeans or Asians own a cell phone, compared to about 50 percent of Americans.

One of the most interesting things about a cell phone is that it is actually a radio -- an extremely sophisticated radio, but a radio nonetheless. The telephone was invented by Alexander Graham Bell in 1876, and wireless communication can trace its roots to the invention of the radio by Nikolai Tesla in the 1880s (formally presented in 1894 by a young Italian named Guglielmo Marconi). It was only natural that these two great technologies would eventually be combined!
In the dark ages before cell phones, people who really needed mobile-communications ability installed radio telephones in their cars. In the radio-telephone system, there was one central antenna tower per city, and perhaps 25 channels available on that tower. This central antenna meant that the phone in your car needed a powerful transmitter -- big enough to transmit 40 or 50 miles (about 70 km). It also meant that not many people could use radio telephones -- there just were not enough channels.

The genius of the cellular system is the division of a city into small cells. This allows extensive frequency reuse across a city, so that millions of people can use cell phones simultaneously.

In a typical analog cell-phone system in the United States, the cell-phone carrier receives about 800 frequencies to use across the city. The carrier chops up the city into cells. Each cell is typically sized at about 10 square miles (26 square kilometers). Cells are normally thought of as hexagons on a big hexagonal grid.

Because cell phones and base stations use low-power transmitters, the same frequencies can be reused in non-adjacent cells. The two purple cells can reuse the same frequencies.

Each cell has a base station that consists of a tower and a small building containing the radio equipment (more on base stations later).






For more information relating to "How Cell Phones Work", please visit our How Cell Phones Work page.

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