Reconfigurable Intelligent Surface Optimal Placement in Millimeter-Wave Networks

TL;DR

This paper develops a model for optimal placement of reconfigurable intelligent surfaces in millimeter-wave networks, considering beam footprint and RIS size, and derives placement strategies to maximize signal quality.

Contribution

It introduces a novel system model linking beam footprint and RIS size, and derives analytical expressions for optimal RIS placement to enhance signal-to-noise ratio.

Findings

Optimal RIS placement depends on system parameters.

Derived closed-form expressions for different RIS sizes.

Simulations confirm the analytical trends.

Abstract

This work discusses the optimal reconfigurable intelligent surface placement in highly-directional millimeter wave links. In particular, we present a novel system model that takes into account the relationship between the transmission beam footprint at the RIS plane and the RIS size. Subsequently, based on the model we derive the end-to-end expression of the received signal power and, furthermore, provide approximate closed-form expressions in the case that the RIS size is either much smaller or at least equal to the transmission beam footprint. Moreover, building upon the expressions, we derive the optimal RIS placement that maximizes the end-to-end signal-to-noise ratio. Finally, we substantiate the analytical findings by means of simulations, which reveal important trends regarding the optimal RIS placement according to the system parameters.