Low-Power Double RIS-Assisted Mobile LEO Satellite Communications
Kunnathully Sadanandan Sanila, Rickard Nilsson, Emad Ibrahim, Neelakandan Rajamohan
TL;DR
The paper tackles the challenge of energy-efficient mobile LEO satellite links by proposing a double-RIS architecture with one RIS near the satellite and another near the ground user. It develops a unified path-loss model that integrates near-field and far-field effects and implements a dual-stage beamforming strategy to maximize signal power while reducing power consumption. Analytical expressions for SNR and data rate are derived, and energy efficiency is formulated with explicit power models for passive and active RIS. Simulations show dramatic power savings (about 40 dB) using a small RIS near the user, demonstrating the practicality of RIS-enhanced NTN uplinks and guiding design choices between RIS sizes and operating modes.
Abstract
We propose a low-power mobile low earth orbit (LEO) satellite communication architecture, employing double reconfigurable intelligent surfaces (RIS) to enhance energy efficiency and signal performance. With a distance between RISs that satisfies the far-field requirement, this architecture positions one small RIS each in the near-field of the satellite's antenna and the user on the ground. Moreover, we develop a path loss model for the double-RIS communication link, considering the near-field and far-field effects. Further, with the help of dual-stage beamforming, the proposed system maximizes the signal power and minimizes power consumption. Simulation results show that the proposed architecture can reduce the power consumption with 40 dB in the uplink, with a small $0.25^2$ $\text{m}^2$ RIS near the user, to communicate in energy-constrained LEO satellite communication circumstances.