Millions of devices – ranging from a large satellite to a tiny earphone – use the radio spectrum on a daily basis. Future mobile networks will require the radio spectrum for high-speed broadband services, low latency applications and massive machine type communications. There is also a mass use of Wi-Fi devices and sensors planned for smart city initiatives. Space networks aim to make increasing use of the radio spectrum to provide internet services via huge constellations of small satellites.

Examples of radio spectrum use are numerous – broadcasting networks, public/private access mobile networks, air-to-ground communication systems, maritime applications, short range devices, disaster monitoring systems, cubesats and radars to name a few. But, the radio spectrum is not endless. So how can we all share this limited resource? This paper looks at the fundamentals of radio spectrum sharing and provides example sharing scenarios analysed by Plum, highlighting the challenges ahead.