Spectral Efficiency Optimization for Hybrid Relay-Reflecting Intelligent Surface

TL;DR

This paper introduces a hybrid relay-reflecting intelligent surface (HR-RIS) that combines active relays and passive reflecting elements, optimizing spectral efficiency through an alternating optimization approach, outperforming traditional RIS.

Contribution

The paper presents the novel HR-RIS concept, formulates its spectral efficiency optimization, and demonstrates its advantages over conventional RIS through analytical and numerical results.

Findings

Significant spectral efficiency improvement with HR-RIS

Effective optimization via alternating optimization method

Analytical and numerical validation of HR-RIS design

Abstract

We propose a novel concept of hybrid relay-reflecting intelligent surface (HR-RIS), in which a single or few elements are deployed with power amplifiers (PAs) to serve as active relays, while the remaining elements only reflect the incident signals. The design and optimization of the HR-RIS is formulated in a spectral efficiency (SE) maximization problem, which is efficiently solved by the alternating optimization (AO) method. The simulation results show that a significant improvement in the SE can be attained by the proposed HR-RIS, even with a limited power budget, with respect to the conventional reconfigurable intelligent surface (RIS). In particular, the favorable design and deployment of the HR-RIS are analytically derived and numerically justified.