Two-Step Adaptive Grouping Access Based on RSMA for Multibeam Satellite System

Multibeam satellite system (MSS) plays an increasingly important role in the future communication system because of the ability to provide seamless information services. However, multibeam technology will cause serious inter-beam co-frequency interference (IBCFI), significantly deteriorating communication performance. Existing IBCFI management schemes mainly depend on precoding technologies, which regard MSS as multi-antenna systems and ignore characteristics of satellite beam gain and the limited computational resources. Meanwhile, terrestrial channels tend to be independent while satellite channels have a high correlation, which is rarely considered by existing work. On the other hand, rate-splitting multiple access (RSMA) has recently emerged due to the advantages of flexible multiple access and robust interference management. Therefore, we design a two-step adaptive grouping access scheme based on the promising RSMA to handle these challenges, where the first step takes the characteristics of satellite beam gain and computational resources into consideration, and the second step optimizes the channel correlation. Building on the two-step adaptive grouping access scheme, we formulate different weighted sum rate (WSR) maximization problems for different user groups. Furthermore, we introduce an improved alternating optimization algorithm to solve these non-convex problems. Finally, simulation results verify the effectiveness of our proposed scheme in WSR and computational complexity.