Cell phones and how do they work?

One of my church members wanted to know how cell phone works in the engineering area and that question was addressed to me. With the little time I have now, I decided to go ahead and find out how these devices actually works. I believe engineering is for the benefit of mankind not because I am going to be an engineer myself but I believe that I can make a big difference in the world if my heart and my mind are together.
Each phone is behaves like a miniature computer. Just like a computer, cell phone contains compact speaker, microphone, key board, a display screen and circuit board with microprocessor. This technology allows you to communicate with other cell phones, computers and exchange data around the globe.
In reality, cell phone is just a flexible radio. Just like a walkie-talkie, cell phone receives and sends radio signals. Wireless networks operate on a grid that divides cities into smaller cells. A cell might cover up to 250 square miles. Every cell uses a set of radio frequencies to provide service in its specific area. In order to limit the signal’s geographic range, the power of these stations has to be supervised all times. Same frequency can be used in nearby cells. That is why, many people can talk simultaneously in the different call throughout the city although they are in the same frequency.
A wireless antenna is stationed in a base station for every cell (http://en.wikipedia.org/wiki/Cell_site). Callers are linked by wireless antenna into local telephone network or a wireless network. Wireless antennas can also be mounted on top of the roof of a building, school, church, trees and etc. In the interstates or highways, taller antennas send signals further distances. Signals also can be obstructed by trees and concrete.
Calls are travelled through a nearby wireless antenna which is switched by one’s wireless carrier to a landline phone system if a person is calling from a cell phone to a wired phone. Meanwhile, long distance calls are being routed to long distance switching area. These days, fiber-optic lines caries digitize version of the voice (http://electronics.howstuffworks.com/question354.htm) . Digital technology converts voice into binary digits 1 and 0 and small packets of these data are relayed through wireless to the receiving end.
Although cell phones are off at times, it can still be communicated with nearby wireless antennas. If you happen to drive by a cell tower, antennas are located at different height to represent different wireless carrier. Therefore, cell phones are just like radios.