Channel Customization for RISs-assisted mmWave MIMO communication systems

Abstract

To address the inherent channel deficiency in strong line-of-sight (LoS) millimeter-wave (mmWave) wireless systems, distributed reconfigurable intelligent surfaces (RISs) are introduced in this study to customize the wireless channel. Capitalizing on the ability of the RIS to reshape electromagnetic waves, we theoretically show that a favorable channel with an arbitrary tunable rank and a minimized truncated condition number can be established by elaborately designing the placement and reflection matrix of RISs. The number of elements needed for each RIS to combat the path loss is also considered in this research. Numerical results show that the effective channel rank can be flexibly and accurately customized according to the required number of data streams. Moreover, utilizing our proposal, every corner in the interested coverage can build the well-conditioned channel with small truncated condition number.