Block Sparsity Based Channel Estimation for IRS-Assisted mmWave MIMO Systems

In this paper, we consider the downlink channel estimation for the intelligent reflecting surface (IRS) assisted MIMO systems in the millimeter wave band. It is challenging to perform the channel estimation for the IRS-assisted wireless communication systems, due to the large amount of passive reflecting elements at the IRS. On account of the inherent sparsity of millimeter-wave channels, the sparse representation expressions of the channel between the base station (BS) and IRS and that between the IRS and user equipment (UE) are obtained separately. Furthermore, the cascaded channel is estimated by solving the BS-IRS and IRS-UE channels in an alternating way. To improve the estimation accuracy and reduce the pilot over-head, the algorithm of the block-structured orthogonal matching pursuit (BS-OMP) is devised to estimate the BS-IRS channel by exploiting its block sparsity. The simulation results show that the proposed method provides the higher estimation accuracy and consumes less pilot overhead by comparing with its counterparts.