Hybrid Precoding for Multiple IRS-Assisted mmWave MIMO Communication Exploiting Mixed Timescale CSI

Intelligent reflecting surface (IRS) has recently emerged as a potential low-cost solution to reshape the wireless propagation environment for improving the spectral efficiency. In this paper, we consider the hybrid precoding for multiple IRS-aided millimeter-wave (mmWave) multiple-input multiple output (MIMO) communication exploiting mixed timescale channel state information (CSI). In particular, the digital precoding matrix at the base station (BS) is optimized by using the instantaneous CSI, while the analog precoding matrix at the BS and the reflection coefficient matrices at the multiples IRSs are optimized by using the statistical CSI. We first formulate the problem to jointly optimize the digital precoding, analog precoding, and the reflection coefficient matrices by using the mixed timescale CSI. Then, an efficient algorithm and a low-complexity algorithm are proposed to solve this problem. Simulation demonstrates that the proposed scheme can significantly improve the spectral efficiency.