Cooperative WMMSE Precoding for Asynchronous LEO Multi-Satellite Communications

Ultra-dense low-Earth-orbit (LEO) networks will integrate with terrestrial networks and play an important role in the future 6G. However, the reused frequency resource leads to serious interference and requires cooperative transmission. For LEO multi-satellite (mSat) systems, synchronous transmitted signals always misalign at receivers due to the large-scale propagation space. In this paper, we design the cooperative beamformer by leveraging the interference asynchrony of LEO mSat communication systems. Consider the coherent transmission, satellites provide signal diversities for users to enhance the reliability. We first derive the asynchronous achievable rate of the mSat system, then propose the cooperative beamforming design based on the weighted minimum mean square error (WMMSE) criterion. Simulation results demonstrate that using the time asynchrony, the proposed method eliminates part of the interference spontaneously, thus improving the spectral efficiency performance.