Every day, we make calls, send messages or connect to the Internet using mobile devices but rarely stop to wonder how it all works. So what is actually going on behind the scenes to enable your mobile to do what it does?
Mobile communications work by using low power radio waves necessary to carry speech and data. When a call is made, the signal is handed across a network of linked geographic areas called cells - hence the term cellphone - until it reaches its destination.
A piece of equipment called a base station transmits signals from one cell to the next, or to land-line networks. Each cell is the area that each base station covers. Base stations are often called masts, towers or cell-sites.
All about base stations
Base station sites come in a range of shapes and sizes and are essential to making mobile phones work. They house radio transmitters and receivers that pick up signals sent from your phone and transfer them to your network operator, so that you can be connected.
Base stations receive signals from mobile phones at ground-level or in buildings and send out signals that you receive as calls, messages, data and other mobile services.
Their construction requires:
Structure for mounting antennas
Antennas for exchanging signals
Electronic equipment for processing signals
Antennas are typically placed high above the ground to transmit and receive signals between base stations. Masts and towers are often used to increase height but you might also see antennas at the top of taller buildings. In some situations, less visibly prominent base station designs may be used.
Different situations, different designs
There are three main types of base station:
Masts or cell-sites
Tall structures that provide the main network coverage. Free-standing masts may be placed at the road-side, in open spaces or wooded areas. Existing buildings are also used so that new construction work is not always needed. Where possible, the visual and environmental impact is limited by slim-line designs, and by trying to make them blend in with the surroundings by painting them, or carefully placing them on existing structures or among trees.
Smaller installations that provide extra capacity and fill in gaps in network coverage. They may be incorporated as building features, or fitted to street-lighting posts or other street features. The visual impact of antennas can be reduced by integrating them with an existing structure.
Other base stations
Small base stations are normally used inside buildings, transport terminals or shopping centers. They use very low power levels, and boost reception where coverage is poor or where there are large numbers of users. Differences in operation mean that 3G networks will need more base stations that are closer to each other, but typically with smaller antennas.
Location, location, location
So, where do mobile communications transmitters get located? Three main factors affect the positioning of base station sites:
Coverage - the area that a base station can service
Capacity - the level of user demand for service within an area
Environment - how a site might affect its surroundings
Each of these is affected by a number of other factors:
Using your phone nearer a base station typically needs a lower signal strength, helping to prolong battery life and reducing radio interference with neighbouring network cells.
The farther you move away from a transmitter, the weaker the signal. Signals are not more intense directly beneath a transmitter, as some people may believe. Radio waves travel outwards from antennas, rather than upwards and downwards. This is why buildings or trees can obstruct the signals.
Environmental features such as hills and trees reduce the strength of radio signals. Towers located on top of hills help boost coverage in such situations.
More base stations are needed in towns and cities, where there are more concentrated numbers of mobile phone users. When base stations are needed closer together, they operate on lower power. All mobile phone signals are controlled and regulated so that they do not interfere with emergency service communications, or TV and radio broadcasting.
Different countries have different regulations and conventions for deciding the location of base stations. As a general guide, these are the main groups who would have a say.
Network operators carefully plan where to site base stations. They need a broad understanding of the properties of radio waves, legislation and public attitudes towards mobile communications.
Operators try to share sites where possible. This can help them ensure that the number and height of masts within a local area best meets the needs of the community. Differences between networks mean this is not always possible.
Local governments and planning authorities are often involved in decisions. It is important for the authorities and operators to co-operate closely together.
Many sites are placed on leased sites in cooperation with the property owners . Property owners will normally require clear assurances on the safety and security of the site.
... and you.
Like water and electricity supplies, mobile communications is a utility provided for the common good. The mobile network industry is encouraged to consult people who live, work or travel near a base station site. And you can normally express your views in a number of ways, helping to ensure that this service is provided in the best way.