Rank Optimization for MIMO Channel with RIS: Simulation and Measurement

TL;DR

An efficient RIS optimization method is proposed to enhance the effective rank of the MIMO channel for achievable rate improvement and reveals a significant increase in effective rank and achievable rate for the RIS-assisted MIMO channel compared to the MIMO channel without RIS.

Abstract

Reconfigurable intelligent surface (RIS) is a promising technology that can reshape the electromagnetic environment in wireless networks, offering various possibilities for enhancing wireless channels. Motivated by this, we investigate the channel optimization for multiple-input multiple-output (MIMO) systems assisted by RIS. In this paper, an efficient RIS optimization method is proposed to enhance the effective rank of the MIMO channel for achievable rate improvement. Numerical results are presented to verify the effectiveness of RIS in improving MIMO channels. Additionally, we construct a 2$\times$2 RIS-assisted MIMO prototype to perform experimental measurements and validate the performance of our proposed algorithm. The results reveal a significant increase in effective rank and achievable rate for the RIS-assisted MIMO channel compared to the MIMO channel without RIS.

Figures (6)

• Figure 1: The considered RIS-assisted MIMO communication system.
• Figure 2: Deployment of the considered RIS-assisted 2$\times$2 MIMO communication system (top view).
• Figure 3: Effective rank versus power ratio of the RIS-assisted channel for different numbers of unit cells.
• Figure 4: Comparison of the achievable rate for the ZF receiver and the upper bound with increasing $\alpha$ when considering different numbers of unit cells.
• Figure 5: A photo of the RIS-assisted 2$\times$2 MIMO communication prototype.