Hybrid Reconfigurable Intelligent Surfaces and Unmanned Aerial Vehicle Assisted Communication

Reconfigurable Intelligent Surfaces (RIS) and Un-manned Aerial Vehicles (UAVs) have emerged as promising technologies for the 6th-Generation (6G) network. The integration of RIS with the UAV (RIS-UAV) can enhance ground communication by providing a 360° panoramic reflection. Existing RIS-UAV mainly considers passive elements which suffer from double path loss problems. This motivates the use of the hybrid RIS-UAV equipped with both active and passive RIS elements. This paper investigates the rate maximisation problem for the hybrid RIS-UAV by optimising the UAV's altitude, transmit power allocation at the base station and hybrid RIS, subject to the hardware power dissipation, transmission power, and flight power. The non-convex joint optimisation problem is addressed using a Genetic Algorithm (GA). The numerical results show that the joint-optimised hybrid RIS-UAV can achieve a rate twice the unoptimised hybrid RIS-UAV and 22 times higher than the conventional passive RIS-UAV.