Double Intelligent Reflecting Surface-Assisted Multi-User MIMO Mmwave Systems With Hybrid Precoding

This work investigates the effect of double intelligent reflecting surface (IRS) in improving spectrum efficient multi-user multiple-input multiple-output (MIMO) network operating millimeter wave (mmWave) band. Specifically, we aim to solve a weighted sum rate maximization problem by jointly optimizing digital precoding at transmitter and analog phase shifters IRS, subject minimum achievable constraint. To facilitate design an solution, first reformulate original into tractable one exploiting majorization-minimization (MM) method. Then, block coordinate descent (BCD) method is proposed obtain suboptimal where matrices are alternately optimized. matrix solved quadratically constrained quadratic programming (QCQP), while shift optimization Riemannian manifold (RMO). The convergence computational complexity analyzed. Finally, simulation results provided verify performance design, as well effectiveness double-IRS spectral efficiency.