On the Fundamental Characteristics of Intelligent Reflecting Surface Enabled MIMO Channels

Smart radio environment (SRE) via reconfigurable and intelligent reflecting surfaces (IRSs) is envisioned to shape wireless communication beyond 5G. In SRE, low-cost, low-power, and passive IRS elements will, in an intelligent manner, alter the phase shifts of incident waves to beamform the reflected signal in the desired direction. SRE challenges the status quo of communication system design as the wireless channel is no longer an impairment but a customizable component for enhancing system performance. In this article, we systematically investigate and visualize the performance of IRS-multiple-input multiple-output (MIMO) channels in a practical outdoor application scenario. Here we use channel gain, rank, condition number, and spectral efficiency heat maps of the coverage area to reveal several underlying characteristics of IRS-MIMO channels under different propagation conditions and array configurations. We also present several observations and insights that have the potential to contribute design guidelines toward IRS-assisted MIMO communication for next-generation networks.