If you have a portable phone that you can carry around with you away from your home, then you have a mobile phone - also called a cell phone - connected to a wireless network. The reason it is called a cell phone network is that the transmission/reception masts communicate only over the cell that they are in. These transmitter/receivers are known as base stations. Each cell uses a different set of frequencies from neighbouring cells, so that each base station knows which its mobile devices are.
Imagine it this way. You are in a cell and your device automatically seeks and then tunes into its local base station. This base station is sending and receiving as though it were a local radio station, say radio 1. The nearby base station is set up as though it were radio 2, and works on a slightly different frequency. This means that any one base station is only dealing with those close to it, not also trying to handle lots of mobile devices far away. This speeds up the rate of communicating.
What is also means is, that when you move away from one cell and into another, the base stations have to know that and 'hand over' your call.
It is done instantly and electronically. You would never know it is happening unless you move out of a region with cells.
What you can also see is that a very large number of base stations with their towers are needed. It is a very expensive business to be in.
In cities, where there are lots of buildings in the way, each cell site may have a range of half a mile (less than a km), while in rural areas, the range may be 5 miles (8km). But it will still mean that some areas are missed as the number of people in an area doesn't warrant having a base station, or there are hills and valleys getting in the way of the base station signal.
