3D spatial–temporal spectrum sensing and sharing for cognitive UAV networks

Unmanned aerial vehicle (UAV) enabled wireless communication networks have attracted significant research attention. With no dedicated spectrum allocated to UAV communications, cognitive radio (CR) technology is considered an important way of supporting UAV communications. In this paper, we study the three-dimensional (3D) spatial–temporal spectrum sensing and sharing for cognitive UAV networks to reuse the spectrum holes. We consider the UAVs randomly and uniformly distributed in one 3D hemisphere and cognitive UAVs perform spatial–temporal spectrum sensing to opportunistically access the licensed spectrum band of the ground base station (GBS). The objective of the considered 3D spectrum sharing networks is to maximize the downlink throughput of cognitive UAV networks with the constraint of interference to the GBS by optimizing the sensing time, power allocation and 3D coordinates of UAVs. Considering the mutual interference between UAVs, we further derive the interf-erence-free transmit probability (IFTP) between UAVs based on the distribution of UAVs. The simulation results show that the achievable downlink throughput of cognitive UAV networks with the proposed 3D spatial–temporal spectrum sharing scheme is about 2.2 times higher than that of the pure temporal spectrum sharing scheme.