Relay-Aided Double-Hop RISs-Empowered Outdoor-to-Indoor Communications

In this letter, we consider a relay-aided double-hop reconfigurable intelligent surfaces (RDH-RISs) empowered outdoor-to-indoor communication system, where two RISs are deployed in a back-to-back manner and connected via a relay that can magnify the signal amplitude. We study system rates under both the single-input single-output (SISO) and general multi-users multi-input multi-output (MU-MIMO) settings. Particularly, we derive the upper bound of the rate under the SISO setting. While under the MU-MIMO setting, we propose a joint optimization algorithm to maximize the weighted sum-rate. Simulation results indicate that RDH-RISs architecture can significantly enhance performance.