On the Secrecy Analysis of a RIS-aided Wireless Communication System Subject to Phase Quantization Errors

In this paper, we analyze the physical layer security of a jamming-aided wireless communication system assisted by a reconfigurable intelligent surface (RIS). Our setup consists of a source node communicating with a destination node with the help of a RIS, and under the presence of a malicious passive eavesdropper attempting to overhear the genuine transmission. Furthermore, an external cooperative jammer is incorporated to reinforce the system's secrecy by broadcasting an artificial noise to disrupt the eavesdropper; such a noise can be removed at the destination. Finally, we assume that the tunable RIS phases based on the channel estimates are subject to quantization errors. By virtue of the well-adopted Gamma and Exponential distributions approximations, an approximate expression for the system's intercept probability (IP) is derived in terms of the main setup parameters. The results show that the greater the number of reflective elements (REs) and jamming power, the better the secrecy, while the number of quantization bits has less impact when exceeding 3 bits. In particular, an IP of 10-3 can be reached with 50 REs even when the legitimate link's average signal-to-noise ratio (SNR) is 15 dB below the wiretap channel's average SNR. Monte Carlo simulations endorse the derived analytical results.