Dynamic Power Allocation Method Based on ZF Precoding for multibeam GEO-LEO Co-existence System

Spectrum scarcity has been an obstacle to preventing the development of satellite communication, sharing spectrum between GEO and LEO has proven to be a promising option to resolve it. However, such a system requires GEO as a primary system and LEO as a secondary system that does not cause harmful interference to primary users, and there only consider the inter-satellite interference in the existing literature to maximize the sum rate of the system. This paper proposes a downlink transmission scheme exploiting dynamic power allocation in conjunction with ZF precoding for a multibeam LEO-GEO co-existence satellite system. The motivation behind the proposed design is to jointly optimize the sum rate and user fairness. In our proposed system, we not only consider inter-satellite interference but also consider intra-satellite interference. We formulate a weighted sum rate maximization problem that incorporates SINR requirements for primary users. Since the optimization problem is non-convex, we adopt a closed-form FP approach to transform it. We validate the proposed method with numerical results, it is shown that our scheme can achieve a good balance between system performance and user fairness.