RIS-NOMA-aided LEO Satellite Communication Networks

Abstract

This paper investigates Low-Earth-Orbit (LEO) satellite wireless communication networks aided by reconfig-urable intelligent surfaces (RISs) and non-orthogonal multiple access (NOMA). To improve the spectrum efficiency (SE) and energy efficiency (EE), we utilize NOMA and RIS technique. First we build the system model, which includes both the line-of-sight (LoS) and non-line-of-sight (NLoS) links. Then, we utilize successive convex approximation (SCA) converting a non-convex problem to a convex one. To solve the problem, a penalty-based iterative algorithm is proposed for minimizing the transmitting power. Finally, our numerical results show that: 1)The energy consumption of active beamforming decreases with the increase of RISs and tends to converge gradually; 2)The power consumption of active beamforming decreases when the remote user and RISs become closer and the number of transmitting antennas (TAs) becomes larger; 3)With more RISs elements, the energy consumption of active beamforming decreases slowly. It follows that there exists a number of RISs which is optimal.