Conclusions and Future Outlook

The future radio communication, fifth generation (5G) and beyond, is expected to provide an order of magnitude improvement in terms of more capacity, higher energy efficiency, lower latency, more mobility, more accuracy of terminal location, increased reliability, and availability. The enhanced Non‐contiguous Orthogonal Frequency‐Division Multiplexing (NC‐OFDM) is one of such multicarrier techniques suitable for future applications, allowing for high transmission flexibility and spectral efficiency while preserving relatively low computational complexity. Moreover, it possesses the ability to flexibly shape and aggregate the available spectrum resources. Another merit of the enhanced NC‐OFDM technique employed in the future cognitive radio‐communication systems is the protection of the Primary Users (PU) obtained by means of the spectrum shaping algorithms and power control. However, the problem of the reduced reception quality of the NC‐OFDM‐based Cognitive Radio (CR) may occur, when the system operates in the presence of high‐power PU‐originating interference in‐band of the Secondary User (SU) receiver.