Synergistic Transmission in RIS-Assisted Power Passive IoT Networks: A WSR Maximization Approach

Abstract

The evolution of 5G-Advanced (5G-A) technology is pivotal for supporting large-scale, high-density device connections in modern power systems. To achieve maintenance-free and spectrum-efficient communications, we propose an uplink reconfigurable intelligent surface (RIS)-assisted multi-user symbiotic radio (SR) architecture specifically for power IoT networks. In this architecture, passive sensors fully leverage primary transmission resources through the reuse of spectrum and energy, providing a feasible solution to the power supply bottlenecks of passive nodes in large-scale deployments. To overcome the severe double-fading effect and multi-user interference inherent in dense grid environments, we formulate a weighted sum-rate (WSR) maximization problem to achieve synergistic enhancement of transmission efficiency for both primary communication links and passive IoT. We further develop an efficient block coordinate descent (BCD)-based algorithm, utilizing fractional programming and quadratic transformation to jointly optimize the active receive beamforming and passive phase shifts. Simulation results demonstrate that the proposed scheme significantly improves the system WSR and exhibits robust performance even under imperfect channel state information, proving its effectiveness for sustainable and high-efficiency connections in future smart grids.