Energy efficiency assessment of wireless system exploiting multiple reconfigurable intelligent surfaces with hardware impairments

This article explores a practical scenario with hardware impairments (HIs) in a multireconfigurable intelligent surface (RIS) assisted wireless system. This approach is based on a mathematical analysis of the performance of the HI-RIS system. To this end, a closed-form expression of the energy efficiency (EE) and its asymptotic behavior, particularly in regions with high transmit power, are derived. Next, an analysis was conducted to compare the EE of the HI-RIS system with those of relevant systems: the ideal hardware (ID)-RIS system, HI-point-to-point (P2P) system (without RISs), and ID-P2P system (without RISs). The numerical findings unequivocally demonstrate that the incorporation of RISs substantially enhances the EE of the HI-RIS system, particularly at high transmit rates. However, at low transmit rates, the EE of the HI-RIS system less than that of the HI-P2P system. This trend is also reflected in the EEs of the ID-RIS and ID-P2P systems. Moreover, the significant impact of HI on the EEs of the HI-RIS and HI-P2P systems is analyzed. The effects of crucial system parameters, such as the number of reflecting elements, frequencies of WiFi networks, and fading order, are comprehensively determined to provide insights into the behaviors of the HI-RIS system. The outage probability and throughput behaviors of the HI-RIS system are also evaluated to comprehensively analyze of the benefits of RISs and the effects of HI. Finally, the accuracy of the derived expressions was verified using Monte Carlo simulations.