  LEO satellite communication has drawn particular attention recently due to
its high data rate services and low round-trip latency. It is low-cost to
launch and can provide global coverage. However, the spectrum scarcity might be
one of the critical challenges in the growth of LEO satellites, impacting
severe restrictions on the development of ground-space integrated networks. To
address this issue, we propose RSMA for CR enabled GEO-LEO coexisting satellite
network. In particular, this work aims to maximize the system's sum rate by
simultaneously optimizing the power allocation and subcarrier beam assignment
of LEO satellite communication while restricting the interference temperature
to GEO satellite users. The problem of sum rate maximization is formulated as
non-convex and a Global optimal solution is challenging to obtain. Therefore,
we first employ the successive convex approximation technique to reduce the
complexity and make the problem more tractable. Then for the power allocation,
we exploit KKT condition and adopt an efficient algorithm based on the greedy
approach for subcarrier beam assignment. We also propose two suboptimal schemes
with fixed power allocation and random subcarrier beam assignment as the
benchmark. Results demonstrate the benefits of the proposed scheme compared to
the benchmark schemes.
