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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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