Asymptotic Achievability of the Cramér-Rao Lower Bound of Channel Estimation for Reconfigurable Intelligent Surface Aided Communication Systems

To achieve the joint active and passive beamforming gains in reconfigurable intelligent surface assisted millimeter wave system, reflected cascade channel needs to be accurately estimated. Many strategies have been proposed literature solve this issue. However, whether Cramér-Rao lower bound (CRLB) of such estimation is achievable still remains uncertain. fill gap, we first convert problem into a sparse signal recovery by utilizing properties discrete Fourier transform matrix Kronecker product. Then, typicality-based estimator utilized carry out task. We show that, through both mathematical proofs numerical simulations, solution letter can asymptotically CRLB.