A Dynamic Subarray Structure in Reconfigurable Intelligent Surfaces for TeraHertz Communication Systems

TL;DR

This paper introduces a dynamic RIS subarray structure and an adaptive BCD-aided beamforming algorithm to enhance THz MIMO communication systems, addressing coverage limitations of traditional RIS configurations.

Contribution

It proposes a novel dynamic RIS subarray structure paired with an adaptive optimization algorithm for improved beamforming in THz MIMO systems.

Findings

The dynamic RIS subarray structure improves coverage and performance.

The adaptive BCD algorithm enhances joint beamforming efficiency.

Numerical results confirm the effectiveness of the proposed methods.

Abstract

Reconfigurable Intelligent Surface (RIS) has become a popular technology to improve the capability of a THz multiuser Multi-input multi-output (MIMO) communication system. THz wave characteristics, on the other hand, restrict THz beam coverage on RIS when using a uniform planar array (UPA) antenna. In this study, we propose a dynamic RIS subarray structure to improve the performance of a THz MIMO communication system. In more details, an RIS is divided into several RIS subarrays according to the number of users. Each RIS subarray is paired with a user and only reflects beams to the corresponding user. Based on the structure of RIS, we first propose a weighted minimum mean square error - RIS local search (WMMSE-LS) scheme, which requires that each RIS element has limited phase shifts. To improve the joint beamforming performance, we further develop an adaptive Block Coordinate Descent(BCD)-aided algorithm, an iterative optimization method. Numerical results demonstrate the effectiveness of the dynamic RIS subarray structure and the adaptive BCD-aided joint beamforming scheme and also show the merit of our proposed system.