Blockage and RIS Cooperative Joint Beamforming for mmWave MIMO Systems

The revised version has been submitted to the IEEE Transactions on Vehicular Technology.

 A reconfigurable intelligent surface (RIS) is a kind of metasurface that provides an adaptable way of controlling the propagation of radio signals in wireless systems, allowing for improved coverage and system efficiency. Instead of the traditional RIS-assisted single-to-multiple reflection channel, we present a time-variant location-based hybrid reflection channel(TL-HRC) model in this paper. The designed TL-HRC model can easily tune a cooperative situation between the mobile blockage and RIS in millimeter wave massive multiple-input and multiple-output systems and satisfactorily scale a high received power gain. Based on the designed TL-HRC model, we establish a joint active and passive beamforming problem for the weighted sum rate maximization and propose an alternative optimization with a RIS element selection (AO-RES) algorithm to tackle the challenging high dimensional coupled parameters. Through simulation experiments the effectiveness of the proposed TL-HRC-based AO-RES algorithm is validated in terms of the weighted sum rate with the case of perfect channel state information.