Integrating Cognitive Radio MIMO UAVs in Cellular Networks for 5G and Beyond

In this paper, we study the performance of deploying multiple unlicensed unmanned aerial vehicles (UAV s) to share the spectrum and the base station of an established primary network in Multiple-Input-Multiple-Output (MIMO) communications. We present a novel power allocation scheme based on a combination of underlay cognitive radio with channel precoding and decoding to maximize the UAVs sum-rate. In the proposed scheme, we jointly use space alignment and successive interference cancellation techniques to minimize and avoid the interference caused on the primary communication. Optimal power allocation scheme for the proposed system is devised. In our simulations, we show that the proposed scheme allows the UAV s to achieve a rate that highly depends on the primary power and interference threshold. In addition, a supplementary rate is achieved when the UAVs transmit in the unused parallel channels called free eigenmodes. The impact of the different system parameters including the number of antennas and the 3D position of the UAVs are also evaluated.