Optimization of IRS-aided Sub-THz Communications under practical design constraints

TL;DR

This paper proposes a simplified yet effective optimization framework for IRS-aided sub-THz communications, leveraging a two-parameter model for meta-surfaces to enhance multiuser network performance with reduced complexity.

Contribution

It introduces a low-complexity model for meta-surfaces and develops optimization algorithms, including asymptotic analysis, to improve system performance in sub-THz environments.

Findings

High communication rates achieved with simple meta-surface model

Asymptotic insights into system behavior with large antenna and surface areas

Performance limits characterized in terms of user support and surface density

Abstract

We consider the optimization of a smart radio environment where meta-surfaces are employed to improve the performance of multiuser wireless networks working at sub-THz frequencies. Motivated by the extreme sparsity of the THz channel we propose to model each meta-surface as an electronically steerable reflector, by using only two parameters, regardless of its size. This assumption, although suboptimal in a general multiuser setup, allows for a significant complexity reduction when optimizing the environment and, despite its simplicity, is able to provide high communication rates. We derive a set of asymptotic results providing insight on the system behavior when both the number of antennas at the transmitter and the meta-surfaces area grow large. For the optimization we propose an algorithm based on the Newton-Raphson method and a simpler, yet effective, heuristic approach based on a map associating meta-surfaces and users. Through numerical results we provide insights on the system behavior and we assess the performance limits of the network in terms of supported users and spatial density of the meta-surfaces.