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 2×2
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