Compressive Cascaded Channel Covariance Sensing for UPA-Type RIS-Aided Dual-Wideband Systems

This letter introduces a novel cascaded channel covariance matrix (C-CCM) estimation method for millimeter wave (mmWave) uniform planar array (UPA)-type reconfigurable intelligent surface (RIS)-aided dual-wideband multiple-input multiple-output (MIMO) systems. We formulate C-CCM estimation as a compressive covariance sensing problem and propose a beam-squint-aware (BSA) cascaded covariance orthogonal matching pursuit (CC-OMP) algorithm. The CC-OMP estimates large-size spatial C-CCMs from small-size temporal covariance matrices derived from the received signals. Simulation results demonstrate the superiority of the CC-OMP over state-of-the-art approaches in terms of normalized mean square error (NMSE).