Multiple spectrum measurement campaigns around the world have shown that even though the frequencies below 6 GHz are very crowded, enough portions of the spectrum remain unutilized most of the time. Even the most heavily employed bands, such as the ones used for television broadcasting and cellular communications, have shown an average occupancy between 25 and 50% [1]. Together with the ever-increasing growth of connected devices in the scope of the Internet of Things (IoT) concept, these have been the main motivational factors for the intensive research in the field of cognitive radio (CR), which empowered by the abilities of the software-defined radio (SDR) devices, can enable the delivery of IoT services, as they operate together with the incumbent users of the existing wireless networks. Consequently, the CR can be utilized for a variety of applications within IoT and the modern systems for delivery of intelligent services, or the traditional standards for wireless data transmission including mobile networks [2]. Therefore, it can be implemented in diverse appliances and professional equipment for integrated navigation, sensing, and communications.

• Antoni Ivanov
• Albena Mihovska
• Krasimir Tonchev
• Vladimir Poulkov

IEEE Aerospace and Electronic Systems Magazine, vol. 33, no. 5-6, pp. 20-33, 2018, DOI: 10.1109/MAES.2018.170098.

https://ieeexplore.ieee.org/document/8361204