Cellular

A cellular network is a radio network made up of a number of radio cells (or just cells) each served by a fixed transmitter, normally known as a (base station). These cells are used to cover dissimilar areas in order to provide radio coverage over a wider area than the area of one cell. Cellular networks are naturally asymmetric with a set of fixed main transceivers each serving a cell and a set of distributed transceivers which provide services to the network's users.
Cellular networks offer a number of advantages over alternative solutions,
increased capacity
reduced power usage
better coverage
A good (and simple) example of a cellular system is an old taxi driver's radio system where a city will have some transmitters based around a city. We'll use that as an example and assume that each transmitter is handled independently by a different operator.