Welcome to this project about personal communication. The most common way of this communication are cellular phones.

INTRODUCTION

Also known as Cellular Radio Telephones, cell phones are wireless and portable. As time passes they get smaller and with more functions. When the first ones came out they were as big as “bricks” and now they fit inside your hand. Now cell phones can have access to internet, mail, videoconferencing, games, etc. You can talk almost from anywhere in the world. Most of the people need them for work or just use them as a communication device. They don't need power outlets or any cable.

Cell Phones use and need cellular towers to be able to communicate These towers can receive signals from 1.5 km and up to 56 km . The spaces that these towers cover are called cells. Many towers can be in the same cell space so that they can manage when there are many cell phone users at the same place. When you are moving and using a cell phone, as you pass from cell to cell, you also pass the cell phone signal to the next tower so your call is not interrupted. The towers send the signal to a switching station which is connected to the telephone system of that company.

Cellular phone systems exist in most of the metropolitan areas of the world and now rural areas are also using this system. These services are usually more expensive than telephone services since cell phones are cordless. PCS (Personal Communication Services) is a new system used for cell phone services. PCS uses digital transmission sand convert what is spoken to digital form so it is transmitted in a better and more efficient way. A very important factor for cell phones is that the base stations use low power transmitters so the same frequencies can be reused as long as they are non adjacent cells.

Here the purple cells can reuse the frequencies

Cell Phones have a database in it so they can store information such as contacts, pictures, sounds, etc. Most of them display the incoming caller's number and the newest ones can show the picture of the caller, which was taken from the camera integrated in it. Another feature is internet and the opportunity to access web sites designed for cell phones, send and receive mail, check the news or weather, etc. The first cell phones were tested around the year 1976 by Illinois Bell in Chicago . The service for these cell phones began around 1985. The cell phone units were very big compared to the ones of today. There was just one antenna in a city or an area. The signals interfered with commercial radios and even worse, the frequencies couldn't be reused because of the lack of technologies we have today. This service was expensive, defective, and there were limited number of channels for the callers. Since people wanted cell phone communications, the FCC (Federal Communications Commission) in the 1990s let up to 6 mobile telephone service providers in each area.

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Here is an example of an old cell phone compared to a new one.

Prices for these services and units have dropped considerably since the big demand and competition between cell phone companies. In the 2001, there were more than 120 million subscribers to the cell phone service. Because of this, the companies created cheaper packages with the most innovative cell phones and since then the prices have dropped a lot.

FUN FACTS

The newest digital cellular's come with entertainment functions such as dice throwing games, to memory and puzzle games.
Approximately 20 percent of American teenagers already own a cellular phone.
About 60 percent of Europeans own a cell phone, compared to about 40 percent of Americans .
The GSM standard for digital cell phones was established in Europe in the mid-1980s -- long before digital cellular phones became commonplace in American culture.
It is now possible to locate a person using a cellular phone down to a range of a few meters, anywhere on the globe.
3G (third-generation wireless) phones may look more like PDAs, with features such as video conferencing, advanced personal calendar functions and multi-player gaming.
From: http://electronics.howstuffworks.com/cell-phone-buying7.htm

Today most people use cellular phones. They keep you communicated with your friends, family, orcoworkers. Every day more areas are covered by cellular networks and the Cellular Radio Telephone service getsbigger and better as days go on.

From : Microsoft Encarta 2004, http://electronics.howstuffworks.com/cell-phone.htm

Carlos Dalmau, American Institute of Monterrey (Mexico).

Date Published: 04/03/05

Date Last Edited: 08/03/05