Design and Optimization on Successive RIS-assisted Multi-hop Wireless Communications

TL;DR

This paper develops a comprehensive model and optimization strategies for successive RIS-assisted multi-hop wireless systems, improving energy efficiency, beamforming accuracy, and signal power in complex environments.

Contribution

It introduces a general multi-hop RIS model, derives beamwidth expressions, and proposes deployment and beam optimization methods with validated simulation and experimental results.

Findings

Enhanced signal power and coverage in multi-hop RIS systems

Improved energy efficiency and beamforming accuracy

Validated effectiveness through simulations and prototype experiments

Abstract

As an emerging wireless communication technology, reconfigurable intelligent surface (RIS) has become a basic choice for providing signal coverage services in scenarios with dense obstacles or long tunnels through multi-hop configurations. Conventional works of literature mainly focus on alternating optimization or single-beam calculation in RIS phase configuration, which is limited in considering energy efficiency, and often suffers from inaccurate channel state information (CSI), poor convergence, and high computational complexity. This paper addresses the design and optimization challenges for successive RIS-assisted multi-hop systems. Specifically, we establish a general model for multi-hop communication based on the relationship between the input and output electric fields within each RIS. Meanwhile, we derive the half-power beamwidth of the RIS-reflected beams, considering the beam direction. Leveraging these models and derivations, we propose deployment optimization and beam optimization strategies for multi-hop systems, which feature high aperture efficiency and significant gains in signal power. Simulation and prototype experiment results validate the effectiveness and superiority of the proposed systems and methods.