On the BER Performance of RIS-Enhanced NOMA-Assisted Backscatter Communication under Nakagami-m Fading

Backscatter communication (BackCom) has been envisioned as a prospective candidate for enabling the sustained operation of battery-constrained Internet-of- Things (IoT) devices. This approach involves the transmission of information by a backscatter node (BSN) through passive reflection and modulation of an impinging radio-frequency (RF) signal. However, the short operational range and low data rates of contemporary BackCom systems render them insufficient on their own to provide ubiquitous connectivity among the plethora of IoT devices. Meanwhile, wireless networks are rapidly evolving towards the smart radio paradigm. Thus, to enhance the coverage range and capacity, reconfigurable intelligent surfaces (RISs) can be incorporated into the existing BackCom systems. RISs employ passive reflective elements to adaptively configure the stochastic wireless environment in a cost-effective and energy- efficient manner. Furthermore, non-orthogonal multiple access (NOMA) can be exploited to improve the spectral efficiency of the BackCom systems. In this paper, we present the design and bit error rate (BER) analysis of an RIS-enhanced NOMA-assisted bistatic BackCom system under Nakagami-m fading channel. Our extensive simulation results reveal the effectiveness of the proposed system over the conventional NOMA-assisted BackCom system without RIS, and demonstrate the impact of various factors, including the power-reflection coefficients, RIS phase-shift designs, number of reflecting elements, RIS location, and split factor, on the BER performance of the proposed RIS-assisted system.