Performance Evaluation for RIS-Assisted Communications with Power Allocation and Phase Shift Optimization

Reconfigurable Intelligent Surfaces (RISs) have the compelling ability of manipulating incident wireless signals upon reflection. Exploiting this ability leads to increasing the quality of service in wireless communications. Employing an RIS to aid in the communication between two single antenna devices in the presence of interference, optimum values for the phase shifts of the RIS are determined. Moreover, a transmit power allocation algorithm is presented for rate maximization. A comparison with relay-assisted communications is also carried out. It is found that the RIS with optimized phase shifts produces higher rates than the relay when the destination is in the vicinity of the RIS. It is also found that the RIS with optimized phase shifts is more energy efficient for a wide range of threshold rates. Furthermore, employing the optimized power allocation algorithm enhances the rate over fixed power scenarios.