Low‐complexity joint active and passive beamforming for RIS‐aided MIMO systems

In this paper, we consider the reconfigurable intelligent surface (RIS)-aided MIMO systems to realize a high quality link between the base station (BS) and the users via a RIS. To achieve this goal, the active beamforming at the BS and the passive beamforming at the RIS should be jointly optimized. However, most of the existing joint optimization schemes that maximize the sum-rate have high computational complexity due to the complex derivative calculations and matrix inversion. To this end, a biologically inspired particle swarm optimization (PSO) algorithm is exploited to solve the non-convex sum-rate optimization problem with low-complexity. Simulation results show that the proposed scheme provides a better trade-off between performance and complexity than existing solutions for RIS-aided MIMO systems.