Compensation of Double Fading Effect via Active RIS to Improve the System Performance

Although reconfigurable intelligent surfaces (RIS) represent a promising technology, the double fading effect remains a significant concern in RIS-assisted systems, as it can degrade overall system performance if the RIS is not optimally positioned. In this paper, we propose a new compensation technique to remove the double fading effect by using an active RIS system. First, the fading between base station (BS) and RIS is compensated at the active RIS by adjusting the amplification factor and phase of the active RIS elements. Then the resultant reflected signal from the active RIS, form of the source signal with residual error, experiences only single fading at the user equipment (UE). The residual error due to the channel fading compensation of the first link at the active RIS is characterized and collaborated with simulation results. The proposed method not only improves the bit error rate (BER) and outage probability (OP) performance but also enhances the physical layer security (PLS) in the presence of eavesdroppers (Eves). The PLS performance of the proposed system is analyzed in terms of secrecy capacity and secrecy outage probability (SOP). The performance of the proposed model is compared with existing state-of-the-arts.