How mobile telephony works

The first practical application of electromagnetic waves in telecommunications dates back to 1895 and Marconi, while in the 1980s and 1990s they began to be used in mobile and satellite communications respectively.

In 1987 as part of the Single European Policy for Telecommunications the Global System for Mobile Communications (GSM) was set up and today operates in more than 210 countries worldwide.

The basic philosophy behind the GSM network is radio coverage of an area so that at any given moment it is possible to connect mobile phones to base stations. Each base station generates radio coverage cells across small geographical areas. For this reason GSM is also known as a cellular system (Diagram 1).

Diagram 3 - Example of cellular telecom system

The size of a cell depends on the expected number of mobile phone users in the area. In sparsely populated areas (rural areas for example) cells are larger with a diameter that may even exceed 35 km. On the contrary, in densely populated areas (such as large cities), cells are small and do not exceed a few hundred meters in diameter. This is because the use of mobile phones in large towns and cities is particularly common and widespread and so more base stations, each one covering a small area, are required to ensure coverage in any specific area. In such cases the operating power level for each base station is very low because otherwise the station would interfere with the operation of other nearby stations and lead to poor quality in communications. Consequently, the more base stations installed in an area the lower the operating power of each one.

Each time you dial a number, the telecom signal is transmitted via electromagnetic waves to the closest base station and from there to the telephone exchange of the recipient's mobile or land-based phone company before finally reaching the dialed number (through telephone lines or again electromagnetic waves, depending on whether it corresponds to a fixed or mobile phone).