Impact of Reconfigurable Intelligent Surface Geometry on Communication Performance

TL;DR

This paper evaluates how different RIS geometries, from linear to cylindrical, affect communication performance metrics like SNR and outage probability, highlighting the importance of geometry in RIS design.

Contribution

It introduces a comprehensive analysis of RIS geometries, deriving effective illuminated surfaces and optimal placement strategies for various topologies.

Findings

RIS geometry significantly impacts SNR and outage probability.

Cylindrical RISs offer benefits in compactness and coverage.

Optimal RIS placement balances active area and received power.

Abstract

When beamforming is applied at the transmitter, only part of reconfigurable intelligent surfaces (RISs) will be active, and it becomes indispensable to study the impact of RIS geometry. This letter aims at evaluating RIS geometry, ranging from linear (1D), and planar (2D), to cylindrical (3D) structures. We first derive the effective illuminated surface of different RIS topologies and determine the resulting signal-to-noise ratio (SNR) and outage probability. Then, we investigate the optimal RIS location to trade off active area versus received power considering near-field propagation. Numerical results quantify the benefit of RIS geometric compactness and provide their applicable ranges.