Joint Beamforming Algorithm for Multi-stream MIMO Systems Assisted by Multiple Reconfigurable Intelligent Surfaces

In recent years there has been a growing interest in reconfigurable intelligent surfaces (RISs) as enablers for the realization of smart radio propagation environments which can provide performance improvements with low energy consumption future wireless networks. However, to reap potential gains RIS it is crucial jointly design both transmit precoder and phases elements. Within this context, paper we study use multiple panels parallel or multi-hop configuration aim assisting multi-stream multiple-input multiple-output (MIMO) communication. To solve nonconvex joint optimization problem elements targeted at maximizing achievable rate, propose novel iterative algorithm based on monotone accelerated proximal gradient (mAPG) method includes an extrapolation step improving convergence speed monitoring variables ensuring sufficient descent algorithm. Based property then present detailed analysis expressions size. Simulation results different scenarios show that combined proposed be effective solution rates.