Why Radio Frequencies Don't Run Out and How Stations Coexist on the Air

Introduction

This article tackles a common misconception about the scarcity of radio frequencies. While in Russia the spectrum in traditional bands is practically exhausted (in Moscow the deficit reached 50%), radio frequencies themselves "don't run out" thanks to the development of new spectrum sharing technologies.

The Deficit Problem

The situation in Russia:

• In Moscow in 2023, the deficit reached 50%
• 5G development requires approximately 800 MHz more below 6 GHz
• The 3.4–3.8 GHz band is occupied by government agencies using outdated equipment

This is not unique to Russia. Around the world, regulators face the same challenge: demand for wireless bandwidth is growing exponentially, while the laws of physics impose hard limits on how much data you can push through a given slice of spectrum.

Why the Spectrum Is Not Infinite

The problem is not the number of hertz available, but that "two signals close in frequency can interfere with each other." Any useful signal occupies a certain bandwidth and requires guard intervals — empty frequency gaps — to avoid bleeding into neighboring channels. The more stations broadcasting in a region, the more crowded the spectrum becomes, and the harder it is to find clean channels.

The Shannon-Hartley Theorem

The maximum data transmission rate is determined by a formula linking bandwidth and the signal-to-noise ratio. The key takeaway: "simply adding more hertz is pointless if you don't fight the noise." This fundamental theorem from information theory places an upper bound on how much data any channel can carry, regardless of how clever your encoding scheme is. To push more data, you need either more bandwidth or a better signal-to-noise ratio — or both.

Traditional Spectrum Sharing Technologies

FDMA (Frequency Division Multiple Access) — divides the available band into non-overlapping frequency channels, assigning each to a different user. Simple but wasteful, since a channel sits idle when its assigned user isn't transmitting.

TDMA (Time Division Multiple Access) — all users share the same frequency but take turns transmitting in assigned time slots. Used in GSM and many other systems.

CDMA (Code Division Multiple Access) — all users transmit simultaneously on the same frequency, but each signal is encoded with a unique spreading code. Receivers decode only the signal matching their code. More efficient, but more complex.

Modern Technologies

OFDM (Orthogonal Frequency-Division Multiplexing) — splits a wide channel into many narrow, orthogonal subcarriers. Because the subcarriers are mathematically orthogonal, they can overlap in frequency without interfering with each other, dramatically improving spectral efficiency. OFDM is the backbone of Wi-Fi, LTE, and 5G NR.

MIMO and Beamforming — Multiple-Input Multiple-Output uses multiple antennas at both transmitter and receiver to send several independent data streams simultaneously over the same frequency. Beamforming focuses the signal directionally toward the intended receiver, reducing interference to others. Massive MIMO, used in 5G, employs dozens or even hundreds of antenna elements to serve many users simultaneously on the same time-frequency resource.

Dynamic Spectrum Sharing (DSS) — allows 4G and 5G to operate simultaneously on the same frequencies, dynamically allocating resources between the two standards based on real-time demand. This is critical for operators transitioning from 4G to 5G, as it eliminates the need to dedicate separate spectrum blocks to each technology.

Advanced Spectrum Sharing Approaches

• LSA (Licensed Shared Access) — guaranteed shared use of spectrum between a primary (incumbent) user and a secondary (mobile) user under a regulatory framework. The secondary user gets guaranteed quality of service, unlike opportunistic approaches.
• TVWS (TV White Spaces) — exploits unused channels in television broadcast bands. In any given location, not all TV channels are in use, and the gaps can be repurposed for broadband access, IoT, and rural connectivity.
• AFC (Automated Frequency Coordination) — a system that determines the allowable transmission power for devices in real time based on their location, the incumbent users nearby, and propagation conditions. Used in the 6 GHz band for Wi-Fi 6E/7.
• OSA (Opportunistic Spectrum Access) — cognitive radio techniques where secondary users dynamically detect and use spectrum that is temporarily vacant, backing off immediately when the primary user returns. This requires sophisticated spectrum sensing or database-driven approaches.

Conclusion

Radio frequencies don't run out thanks to the continuous improvement of methods for efficient spectrum use. The key insight is that spectrum is not like oil — it is not consumed when used. A frequency can be reused in a different location, at a different time, with a different code, or in a different spatial direction. The entire history of wireless communications is a story of finding ever-more-clever ways to share this reusable resource through intelligent allocation across frequency, time, code, and space. As each generation of technology squeezes more bits per hertz out of the available spectrum, the effective capacity of the airwaves continues to grow, even as the underlying physics remains unchanged.