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How do mobile devices work?
Mobile devices 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 (often called masts or antennas), which sends the signal to a digital telephone exchange and on to the main telephone network. This connects the signal to the receiving device, again via a base station (if it is another mobile device). Without base stations mobile devices will not work and we cannot connect our customers’ calls.
Mobile devices use the minimum transmit power needed to communicate with the base station. This automatically adjusts according to the signal at the base station. The better the signal the lower the transmitted power needed from the mobile device. The power needed depends on a range of factors, including:
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The distance between the mobile device and the base station |
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The operating frequency band at a given time |
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The service the mobile device is being used for (e.g. texting, data or voice calls). |
Mobile devices 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 device automatically adjusts its own transmit power to maintain the minimum 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.
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 a radius of several kilometres. Cells in urban areas typically cover up to a two kilometre radius. The smallest cells, covering a few tens or hundreds of metres, 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 connections 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 devices, from more locations, and for coverage to be continuous when moving around.