Onboard Attitude and Hybrid Beamforming Joint Optimization for LEO Satellite MIMO Systems

This paper investigates the joint optimization of satellite attitude and hybrid analog-digital beamforming (HBF) for low Earth orbit satellite multi-user MIMO communication systems. By introducing satellite attitude as an additional optimization variable, the directional characteristics of the antenna radiation pattern are exploited to enhance system performance. To achieve this, a sum-rate maximization problem is formulated and transformed into an equivalent weighted modified mean square error (MSE) minimization problem. A closed-form solution-assisted collaborative optimization (CSACO) framework is proposed to address the problem. In this framework, we leverage closed-form solutions for precoding and the modified MSE factor to reformulate the attitude optimization problem. By applying manifold optimization and sequentially updating the closed-form solutions, the algorithm converges efficiently to a stationary point, making it well-suited for resource-constrained onboard processing. Simulation results show that the proposed CSACO framework significantly outperforms baseline methods, adaptively optimizing both satellite attitude and HBF based on varying power budgets and user locations.