How do mobile phones work?

Without base stations mobile phones will not work and we cannot connect our customers’ calls. Base stations are often called masts or antennas, as these are the most visible parts.

Mobile phones use radio frequency (RF) fields to send and receive calls, texts, emails, pictures, web, TV and downloads. An RF signal is sent to the nearest base station, which sends the signal to a digital telephone exchange and on to the main telephone network. This connects the signal to the receiving phone, again via a base station (if it is another mobile phone).

Click one of the handsets to see how RF signals travel across mobile and fixed-line networks.

Mobile phones connect to the base station providing the best signal – usually the nearest. As a person moves away from the base station the signal becomes weaker, so the mobile phone automatically adjusts its own RF field strength to maintain the minimum level needed to communicate with the base station.

The area covered by a base station is known as a cell.

Each cell is usually split into three sectors, which overlap with the sectors of neighbouring cells to create an uninterrupted network. When people travel, the signal is passed from one base station to the next, and typically never has to travel further than the nearest base station.

Click and drag the handset to see how the signal is passed from one base station to the next.

The size and shape of each cell is determined by the features of the surrounding area, such as buildings, trees and hills, which can block signals. Cells are largest in flat open landscapes, where they can cover up to a five kilometre radius. Cells in urban areas cover up to a two kilometre radius. The smallest cells are in built up areas, where micro-cell base stations are used to provide extra coverage and capacity.

Each base station can only handle a limited number of calls at a time. In areas of high demand, additional antennas are sometimes added to a base station to send and receive more calls and other mobile services, or an extra base station is installed.

All this means that a large number of base stations are needed to allow more people to use mobile phones, from more locations, and for coverage to be continuous when moving around.