STAR-RIS Assisted Full-Duplex Systems: Impact of Correlation and Maximization

We focus on the sum-rate performance of a full-duplex (FD) communication system assisted by a simultaneous transmitting and reflecting reconfigurable intelligent surface (STAR-RIS). Contrary to previous work, we account for the unavoidable spatial correlation at the STAR-RIS, and we result in closed-form expressions based on statistical channel state information (CSI), expressed by large-scale statistics. Moreover, we propose a novel maximization of the sum-rate by optimizing simultaneously both the amplitudes and the phase-shifts of the STAR-RIS. This method has a reduced overhead, which is quite important on STAR-RIS systems that are implemented with double elements compared to conventional-RIS.