Movable Antenna-Aided Interference Mitigation for LEO-GEO Spectrum-Sharing System

The increasing demand for spectrum resources has necessitated spectrum-sharing between Low Earth Orbit (LEO) and Geostationary Earth Orbit (GEO) satellite systems, introducing the risk of inter-system interference. This interference degrades communication performance, making effective mitigation strategies critical. Unlike existing works that utilize fixed-position antennas, this paper proposes a novel interference mitigation scheme for LEO-GEO spectrum-sharing system, aided by movable antennas (MAs). Specifically, the LEO satellite is equipped with MAs which fully leverage spatial degrees of freedom to enhance LEO system service and mitigate interference. To achieve these objectives, we formulate a max-min signal-to-interference-plus-noise ratio (SINR) optimization problem, subject to LEO-GEO interference mitigation constraints. Due to the non-convex nature of the proposed problem, we design an alternating optimization algorithm, which can optimize signal-to-leakage-noise ratio precoding, power allocation, and MA positions alternatively and jointly. Simulation results demonstrate that the proposed scheme significantly improves the worst LEO user's SINR while ensuring that interference to GEO terminals remains below a specified threshold.