Beamforming and Interference Cancellation for RIS-Assisted HAP-D2D Communication Systems.

Reconfigurable intelligent surface (RIS) is recently envisioned as a potential technology to improve spectrum efficiency with much lower energy consumption. In this paper, we investigate the ergodic achievable rate performance of RIS-assisted high altitude platform (HAP) device- to-device (D2D) communication systems under limited feedback system. Both beamforming (BF) and interference cancellation (IC) strategies are taken into consideration. We first derive the analytical tight bounds of the ergodic achievable rate (EAR) for BF strategy and IC strategy, respectively. Then, an efficient mode switching method between BF strategy and IC strategy is proposed to meet the dynamic network topologies.