Today, people take it for granted that they can make phone calls or transmit data wherever they are and whenever they want. What is the technology behind this?
Electromagnetic fields - the basis for mobile communications
Electromagnetic fields are a natural phenomenon. Light, for example, consists of electromagnetic fields. An electromagnetic field is propagated at the speed of light in a wave-like manner, transporting energy as it does so. Mobile telecommunications uses electromagnetic fields to transmit voice and data.
Radio waves - carriers of information for radio, TV and mobile communications
Electromagnetic fields can be generated by technical means. They arise wherever electric current flows, for example in electrical appliances such as hairdryers, electric razors and TV sets. In these cases, the fields are generally a side effect whereas in mobile communications they are generated specifically to transmit information.
These propagating electromagnetic fields are also referred to as radio waves. In technology environments, radio waves are distinguished by frequency, field strength and waveform.
Base stations - nodes in the mobile communications network
To ensure that we can make mobile calls from any location, mobile communications requires a large number of mobile communications base stations. Each of these base stations has a transmitter as well as a receiver.
When we make a call, the cell phone sets up a radio link to the nearest base station. The station's antenna receives the signals and forwards them to the nearest mobile switching center over cable or microwave link. The call is then transferred to the fixed network and passed to the required telephone line. If the called party is also using a cell phone, the call passes from the fixed network via a mobile switching center and the nearest base station to his or her mobile phone.
Radio cells - full coverage in urban and rural areas
Each base station can only handle a certain number of calls and transmit a certain volume of data. It therefore only serves a narrowly defined area, the radio cell.
Radio cells vary in size, depending on the anticipated number of users and the mobile communications frequencies used. Since most people place calls within cities and villages, many base stations with small radio cells have been set up in these regions.