Performance Analysis of RIS-Aided Multibeam Satellite Communication Systems

Multibeam satellite communication (SatCom) with frequency reuse configuration is a promising technology to provide wide coverage and high-throughput data delivery services. However, the performance of a SatCom system is limited by the long propagation distance and potential obstructions between the satellite and ground users. To overcome the performance limitation, reconfigurable intelligent surfaces (RISs) have been considered to enhance the received signal strength at the receiver and provide a virtual line-of-sight path for detouring obstacles. On the other hand, the reflection of signals at RISs brings another challenge regarding frequency reuse configuration since RISs may amplify not only the desired signal but also interbeam interference due to the satellite antenna radiation patterns. In this article, the impact of the frequency reuse factor on the sum rate of an RIS-aided multibeam SatCom system is analyzed. Also, to reflect a practical environment, various practical parameters, such as environmental attenuation caused by rain fading and distortion noise from the hardware impairments, are considered. The closed-form expression of the ergodic sum rate of an RIS-aided multibeam SatCom system is derived using asymptotic and distance-restricted approximations. Simulation results show that the ergodic sum rate obtained from our analysis closely aligns with the actual result. The results also show that the optimal frequency reuse factor can be deterministically obtained according to the available number of RIS elements and the level of hardware impairments.