Robust IRS-Aided Secrecy Transmission With Location Optimization

Abstract

In this paper, we propose a robust secrecy transmission scheme for intelligent reflecting surface (IRS) aided communication systems. Different from all the existing works where IRS has already been deployed at a fixed location, we take the location of IRS as a variable to maximize the secrecy rate (SR) under the outage probability constraint by jointly optimizing the location of IRS, transmit beamformer and IRS phase shifts with imperfect channel state information (CSI) of Eve, where we consider two cases: a) the location of Eve is known; b) only a suspicious area of Eve is available. We show a critical observation that CSI models are different before and after IRS deployment, thus the optimization problem could be decomposed and solved via a two-stage framework. For case a), in the first stage, universal upper bounds of outage probabilities only related to the location of IRS are derived which can be optimized via successive convex approximation (SCA) method. In the second stage, we develop an alternative optimization (AO) algorithm to optimize beamformer and phase shifts iteratively. For case b), we propose a Max-Min SR scheme based on two-stage framework, where the location of IRS is optimized based on the worst location of Eve. Simulation results indicate the importance of the location of IRS optimization.

Impact of Phase-Shift Error on the Secrecy Performance of Uplink RIS Communication Systems

“…In addition, there exists only one optimal location for the RIS which is around 25m. Thus, in passive and active RIS schemes, different from the conventional RIS deployment, the RIS should be deployed close to the users to achieve better secrecy performance [47], [48]. On the other hand, the EH-RIS scheme achieves better secrecy performance when the RIS is located either near the BS or the users.…”

“…In [35], RIS has been used to perform secure transmission from a multiple antennas transmitter to a multiple antennas legitimate receiver. Further work in [36] considered the secrecy transmission in a RIS-aided multiple antenna communication, where the secrecy rate was improved by optimizing the RIS location. In [37], an active RIS-aided multiple antennas PHYSec transmission scheme was considered, where the active RIS was designed to amplify the signal actively.…”

Applications of Absorptive Reconfigurable Intelligent Surfaces in Interference Mitigation and Physical Layer Security

“…The above fractional programming problem can be solved through the Dinkebach algorithm by introducing a slack variable λ, in which case problem (30) becomes…”

“…The joint transmit beamformer and RIS phase shift design that maximizes the SR has been investigated in [26]- [29] for the case of perfect channel state information (CSI). Scenarios with and without partial knowledge of the eavesdropper CSI were considered in [30] and [31], respectively. The authors of [31] proposed a two-step scheme to maximize the jamming power received at Eve while simultaneously achieving a given quality of service at Bob.…”

“…The authors of [31] proposed a two-step scheme to maximize the jamming power received at Eve while simultaneously achieving a given quality of service at Bob. A similar goal was addressed in [30], where the RIS location was further optimized to improve performance. An RIS is leveraged in [32] for secure parameter estimation at a wireless sensor network fusion center operating in the presence of an eavesdropper.…”