Radio spectrum

Every wireless connection works via invisible waves that travel through the air. These waves oscillate at different speeds. The number of oscillations per second is called frequency, measured in hertz. The radio spectrum is the ordered sequence of all frequencies that can be used for wireless transmission. You can picture it like a very long piano keyboard: on the far left the slowly oscillating, low tones, on the far right the fast, high ones. Radio stations, mobile networks, WiFi, GPS and satellites each occupy their own keys and must not encroach on one another.

A scarce resource that costs billions

The radio spectrum cannot be multiplied. You can widen a highway or lay another fiber optic cable, but you cannot invent new frequencies. The usable range extends roughly from a few kilohertz up to around one hundred gigahertz. Everything within it is already allocated. It is precisely this scarcity that makes radio frequencies so valuable.

That is why states auction usage rights to network operators. Germany’s 2019 5G auction brought in around 6.5 billion euros, while the UMTS auction in 2000 raised roughly 50 billion euros. These sums regularly appear in economic news. They weigh on telecom companies' balance sheets for years and influence how quickly new networks are built.

A second reason for regulation is technical in nature. If two systems transmit simultaneously on the same frequency in the same location, they interfere with each other. In the worst case, aviation radio fails or an emergency service cannot reach its dispatch center. Without binding allocation, radio traffic would be pure chaos.

Why high frequencies are fast but short of breath

The spectrum is divided into bands, that is, sections with fixed boundaries. A band such as 800 megahertz or 3.6 gigahertz belongs to one operator for a specific region and a specific period of time. Within its band it may transmit, outside it may not. In Germany, the Bundesnetzagentur (Federal Network Agency) monitors this and can penalize violations.

The decisive factor is the trade-off between range and speed. Low frequencies have long waves. They penetrate walls and forests well and reach many kilometers. However, they carry less data per second. High frequencies are the opposite: very high data rates, but even a house wall or rain can stop the signal.

That is why mobile networks combine several bands. In rural areas, low frequencies ensure that there is reception at all. In city centers or stadiums, high frequencies from many small antennas deliver the necessary capacity. A common misconception is that 5G is automatically a specific frequency band. 5G is a transmission technology and runs on very different frequencies depending on how it is deployed.

From the WiFi router to the World Radiocommunication Conference

In everyday life you encounter the radio spectrum every day, usually without noticing. Your WiFi router offers two ranges: 2.4 gigahertz reaches further through the apartment, 5 gigahertz is faster but more sensitive. Bluetooth headphones also use 2.4 gigahertz, which is why they sometimes stutter on crowded trains. These bands are unlicensed, anyone may use them, and accordingly they are crowded.

In the news, the term mainly comes up in connection with frequency auctions and disputes over allocation. Broadcasters, mobile operators, the military and satellite operators compete for the same sections. Every three to four years, the United Nations' World Radiocommunication Conference negotiates which band is intended for what purpose worldwide. Without this coordination, a mobile phone would simply not work abroad.

The spectrum is also relevant to AI topics. Large language models run in data centers, but the response has to reach the user’s device. Self-driving cars, connected factories and drones need reliable wireless connections with low latency. For industrial facilities, the Bundesnetzagentur now allocates dedicated frequencies for private campus networks on company premises.