The Mobile Telephone Network

Another name for mobile telephones, used commonly in North America, is cell phones. This name gives us a bit of a hint as to how mobole phones work. As we saw earlier a problem encountered by early mobile phone networks was that there weren't enough channels (or frequency's) available for them to be used widely. The modern day mobile phone network has overcome this problem by splitting area's up into different cells (hence the name cell phone). Think of a typical city, such as London. It covers a large area, but in terms of a mobile phone, it is split into many smaller area's, or cells.

How does splitting a city into cells solve the frequency problem?

Good question! Because the area a cell has to cover is fairly small (normally around 10 square miles) the power at which it sends out signals is much lower than if it was trying to send them out to a much larger area. This means that many different cells can use the same frequencys as long as any of the cells next to it are not using those (as if they were a mobile phone wouldn't know which cell it was in!).

An example of how this works is shown below

Image courtesy of Howstuffworks.com

In the picture above the two cells which are dark purple and have red circles around them would be able to use the same frequencys as they are not next to each other, so there is no chance of a mobile phone thinking it is in another cell.

The annimation above shows how a users mobile phone registers with different transmitters as it passes from one cell to another. The black line in the center shows the boundary between the two cells.

There have been verious 'stages' of development for mobile phones, and these are called generations (e.g., the term 3G stands for 3rd generation). To find out about the different different generations of mobile phones, click here.