How mobile communications work
Today, it is natural to make calls or transmit data anytime, from anywhere. What technology makes this possible?
Electromagnetic fields—the basis of mobile communications
Electromagnetic fields are a natural phenomenon that includes light, for example. An electromagnetic field travels in waves at the speed of light, carrying energy as it goes. Mobile communications use electromagnetic fields to transmit voice and data.
Radio waves—carriers of information for radio, television, and mobile communications
Electromagnetic fields can be generated technologically. They also occur wherever electricity flows—for example, in electrical devices such as hair dryers, electric shavers, and televisions. In mobile communications, however, they are generated deliberately to transmit information.
Electromagnetic fields that travel outward are also called radio waves. Technology distinguishes them by their Frequency, Field strength, and signal shape.
Base stations—hubs of the mobile network
To make mobile calls from wherever we are, we need a large number of mobile Base stations. Each one has transmitting and receiving components.
When you make a call, your cell phone establishes a radio connection with the nearest Base station. Its receiving antenna picks up the signals and forwards them by cable or microwave link to the next radio switching center. There, the call is routed to the fixed-line network and connected to the intended phone line. If the recipient is also using a cell phone, the call travels from the fixed-line network back through a radio switching center and the nearest Base station to reach them.
Radio cells—coverage across cities and rural areas
Each Base station can handle only a certain number of calls at the same time and transmit a specific volume of data. It therefore serves a relatively limited area, known as a Radio cell.
Radio cells vary in size depending on the expected number of users and the mobile frequency used. Because most people make calls and access data in towns and cities, there are more Base stations there with smaller Radio cells to provide reliable mobile coverage. A distinction is made between macro cells and small cells.
Macro cells provide mobile coverage for larger areas, with a radius of up to 12.4 miles. Small cells provide additional capacity in places with heavy usage, such as train stations, shopping centers, and soccer stadiums, complementing the mobile network of macro cells.
From GSM to 5G – different generations of mobile technology
2G – GSM
Around three decades ago, the introduction of 2G technology (GSM) transformed the world of mobile communications and created the technical foundation for digital mobile networks. This technology is now outdated and is expected to be retired from the Telekom network in mid-2028. As part of the ongoing network modernization, areas that currently have 2G coverage but not 4G coverage will receive 4G/5G coverage before 2G is retired. Afterward, the available 2G frequencies will also be used for the newer technologies, further improving network speed and performance.
3G - UMTS
GSM was primarily used to cover large areas. UMTS technology, by contrast, offered specific benefits in densely populated areas where many users are on the move at the same time. The UMTS standard laid the foundation for mobile data communication, but it is outdated compared with the more modern 4G and 5G radio standards. Telekom therefore shut down its UMTS network in 2021 and now uses the frequencies that became available for the more capable 4G and 5G technologies.
4G - LTE
LTE is the fourth generation of mobile technology (4G). With its substantially higher data capacity, LTE meets the growing needs of a digital society: More and more mobile users want to do more than make calls on the go—they also want to use digital services and all the possibilities they offer while they are out and about.
5G – A communication standard, not just a mobile standard
5G is the current generation of mobile communications. It provides the foundation for new customer experiences, such as augmented reality games and the networking of industrial machines and smart devices. The technology also supports the digital transformation of many areas of life. The 5G rollout benefits not only cities but also rural regions: Since the end of 2025, the mobile standard has reached 99 percent of Germany's population.