How Cellular Works

The Phone

Think of a cellular phone as an advanced radio, since it operates by sending and receiving radio waves, although the waves travel on different bands than your AM or FM radio.  Cellular phones come in many different shapes and sizes, but it’s what’s on the inside that counts when it comes to making and receiving calls.  Each mobile phone is equipped with components that include an antenna, keyboard, a circuit board containing microprocessors, a display screen, a microphone, a miniature speaker, and a battery.   When in range of a wireless network, these technologies inside your phone band together to communicate with others possible by way of cellular telephone calls.

Since wireless phones operate by way of radio frequencies and are connected to an extremely large network, users can call anywhere in the world at any time.  In this day and age of advanced cellular services, not only can you call anywhere in the world, but the technology inside your phone will also allow you to send and receive data from another wireless device or even a personal computer. 

The Network

Each cellular phone provider in the United States operates a radio network that operates on a grid using the 850 or 1900 MHz frequency ranges (other bands, including 900 and 1800 MHz are used in other parts of the world).  A grid is used to allow for cities and other heavily populated areas to be divided into cells. Depending on the provider’s network, one cell may cover up to 250 square miles each.  Cells employ radio frequencies that transmit at the 850 and 1900 frequencies.  Each wireless provider’s cell must maintain a particular signal strength for the area it represents.  This is so the same frequencies can be used in neighboring cells while still allowing for multiple cellular phone users to talk at once.

The Cell

In the past service providers were required to put all of their faith (and signal strength) in large radio towers that transmitted their signal across entire cells.  With upgraded technology including signal repeaters, providers can spread smaller wireless antennas almost anywhere inside a cells network to assist in connecting callers to their requested destination.  As such, strategically placed repeaters are now bringing cellular service to previously unreachable locations including commuter trains that travel underground and sporting arenas, skyscrapers, and other large buildings whose dense concrete structures previously prevented their inhabitants from receiving a strong cellular signal.

Features

With advancements in technology combining with the ingenuity of the wireless phone manufacturers, more and more advanced mobile devices continue to appear on the market.  Some of the new features you can find on cell phones include FM radios and digital audio players, mp3 and polyphonic ring tones, games with 3D graphics, and even Microsoft Office software.  The addition of digital cameras to many of today's phones has also made it possible for users to personalize their mobile devices with photos for everything from screensavers to Caller ID messages.   

The data services and features found inside new wireless devices continue to advance as well.  We thought text messaging was impressive until cellular manufacturers introduced mobile devices that can send and receive picture and video email, surf the web, receive a fax, or even be used to play a game of online poker.

Making a Call

No matter if you flip open, slide, or just dial your phone to begin a call, by the time you enter the first number it has already started searching for a signal.  The information your telephone provides to the network includes the name of your wireless provider and the number of your cellular telephone.  Once that information has been determined your call is transmitted according to what type of telephone number you have dialed:

Wireless to Wireless
The wireless antenna closest to you will assist in completing this call by either sending it through the wireless network to the cell site nearest who you are calling or it may go through a landline network to your caller’s wireless carrier.   

Wireless to Landline
Starting at the wireless antenna again, your call is transferred by your wireless carrier to an existing landline telephone system.  This call is now transmitted just like you were calling from a landline phone.

Wireless to Long Distance or International
For this type of call, assistance from a long distance switching center is required.  The call is now placed in their hands and is transferred using their fiber-optic network to the recipient’s phone.   
So remember next time you are making a call that all of this is happening in the small amount of time that your phone rings and the person on the other end answers.  

Being Heard

Now that you are connected, it’s important for the person on the other end to be able to hear you.  Wireless phone calls are made possible by digital technology that actually converts your voice into a bit of data with a single binary value of either 0 or 1.  The wireless network you are using is now able to send your converted voice through the system to the receiver’s phone.  A final reversal of the binary digits occurs turning the codes back into your voice.       
 

Sending Data

The same concept is used for sending data as for sending your voice.  Instead your voice being converted into binary digits, it's whatever form of data you may be trying to send that gets transmitted.  Examples of data being sent today include e-mail, text messages, and digital pictures.  Since your wireless phone is a computer connected to a radio, it actually works exactly like your PC does to send and receive data.

Since a bit is also the smallest unit of data in a computer and is utilized to send information over the Internet, the wireless telephone is only going to continue to advance when it comes to sending data. The improvements to the wireless network we use today will only make the amount and type of data we are able to send from our wireless phones grow.