This article delves into the optimal design of transmitting signals with artificial noise (AN) in reconfigurable intelligent surface (RIS) assisted secure communication system. Due to the introducing of RIS, injecting AN into null space of Alice-Bob channel is not optimal. Our approach commences with the formulation of the signal and AN design as an optimization problem, with the objective of maximizing the secrecy rate while conforming to the secrecy outage probability (SOP) constraint. Through constructing an equivalent channel model for the RIS-assisted communication scenario, we deduce the optimal solution which is represented as transmitting direction and corresponding power allocation for both information-bearing signal and AN. The research results contribute a theoretical objective for the practical design of AN transmission scheme in RIS-assited secure communication scenarios.
This article delves into the optimal design of transmitting signals with artificial noise (AN) in reconfigurable intelligent surface (RIS) assisted secure communication system. Due to the introducing of RIS, injecting AN into null space of Alice-Bob channel is not optimal. Our approach commences with the formulation of the signal and AN design as an optimization problem, with the objective of maximizing the secrecy rate while conforming to the secrecy outage probability (SOP) constraint. Through constructing an equivalent channel model for the RIS-assisted communication scenario, we deduce the optimal solution which is represented as transmitting direction and corresponding power allocation for both information-bearing signal and AN. The research results contribute a theoretical objective for the practical design of AN transmission scheme in RIS-assited secure communication scenarios.
This paper addressed the optimal design of signal with artificial noise in Reconfigurable Intelligent Surface (RIS) assisted physical secure communication system, which becomes complicated due to the introduction of an auxiliary and reconfigurable communication link. We firstly formulate the optimal form design of the transmitted signal and artificial noise (AN) as a problem of maximizing secrecy capacity under the constraint of secrecy outage probability (SOP). By constructing an equivalent channel for RIS-assisted communication scenario, the optimal solution is derived which involves transmit direction vector, transmit power vector and power splitting factor. The results can provide guidance for the secure transmission design of confidential communication systems in consumer Internet of Things (CIoT) scenarios.
In this paper, we consider a reconfigurable intelligent surface (RIS)-assisted multiple-input multiple-output (MIMO) secure communication system, where only legitimate user's (Bob's) statistical channel state information (CSI) can be obtained at the transmitter (Alice), while eavesdropper's (Eve's) CSI is unknown. Firstly, the analytical expression of the achievable ergodic rate at Bob is obtained. Then, by exploiting Bob's statistical CSI, we jointly design the transmit covariance matrix at Alice and the phase shift matrix at the RIS to minimize the transmit power of the information signal under the quality-of-service (QoS) constraint of Bob. Finally, we propose an artificial noise (AN)-aided method without Eve's CSI to enhance the security of this system and use the residual power to design the transmit covariance for AN. Simulation results verify the convergence of the proposed method, and also show that there exists a trade-off between the secrecy rate and QoS of Bob.
This paper analyzes the secrecy performance of a reconfigurable intelligent surface (RIS) assisted wireless communication system with a friendly jammer in the presence of an eavesdropper. The friendly jammer enhances the secrecy by introducing artificial noise towards the eavesdropper without degrading the reception at the destination. Approximate secrecy outage probability (SOP) is derived in closed form. We also provide a simpler approximate closed-form expression for the SOP in order to understand the effect of system parameters on the performance and to find the optimal power allocation for the transmitter and jammer. The optimal transmit and jamming power allocation factor is derived by minimizing the SOP assuming a total power constraint. It is shown that the SOP performance is significantly improved by the introduction of the jammer and a gain of approximately 3 dB is achieved at an SOP of 10–4by optimally allocating power compared to the case of equal power allocation.
In this article, the physical layer security (PLS) is investigated for reconfigurable intelligent surface (RIS)-aided wireless communication systems, where one RIS is deployed to assist the communications between a pair of transmitter (Alice) and receiver (Bob), under a passive eavesdropper (Eve) attack. For the Eve, different from the bounded channel state information uncertainty model, the distribution of the Eve’s location is introduced into the wiretap link. In the proposed system, considering that the Eve can overhear signals transmitted from Alice or reflected by the RIS, two scenarios are studied for RIS-aided secure communication systems: one is that the Eve distributes close to Alice without the RIS orientation, and the other is that the Eve locates close to Bob and in the presence of the RIS. After investigating the probability distribution functions of the Eve’s location and the wiretap link, the novel cumulative density functions (CDFs) of the received signal-to-noise ratios (SNRs) at the Eves are, respectively, derived for the two considered scenarios, taking into account the effects of RIS reflection coefficients, pathloss, and Eve’s location distribution. The closed-form expressions for the probability of the nonzero secrecy capacity and the ergodic secrecy capacity are obtained, providing insights into the impact of the Eve’s location uncertainty and the RIS design on the secrecy performance. Moreover, based on the derived CDFs for received SNRs at Eves, the secrecy outage probabilities are, respectively, analyzed. Specifically, under the constraint of the secrecy outage probability, the closed forms of the minimum required SNRs at Bob and the number of RIS elements are also obtained. Simulation and analytical results corroborate the derived expressions and reveal the tradeoff between the system’s energy efficiency and the number of RIS elements.
Abstract This paper investigates a cooperative beamforming (BF) and jamming schemes in active reconfigurable intelligent surface (RIS)-assisted secure communication network, where an active RIS perform reflecting BF and a friendly jammer transmits jamming signal to enhance the security. Specifically, we consider a secrecy rate maximization problem under specific power constraints by assuming that perfect channel state information (CSI) of the eavesdroppers (Eves) can be obtained by the transmitter (Alice). Using the semidefinite relaxation (SDR) and CharnesCooper transformation, we address this problem by performing a one-dimensional search which involves solving a sequence of semidefinite programs (SDPs). For more practical scenario that perfect CSI of the Eves can not be obtained by Alice, a robust joint design of BF and jamming is proposed and the worst-case secrecy rate optimization is solved by using the S-procedure and its extension. Finally, simulation results demonstrate the performance gains of the proposed designs.
Ensuring signal confidentiality against eavesdroppers is particularly challenging, especially with imperfect channel state information (CSI). To address this, we propose a novel approach leveraging reconfigurable intelligent surfaces (RISs) to enhance security and optimize transmission performance. This paper focuses on secure communication in symbiotic radio (SR) systems by investigating cooperative jamming-assisted transmission with RISs, providing a robust solution to these challenges. RIS-I, acting as a secondary transmitter (STx), multicasts confidential signals from the primary transmitter (Alice) to a primary user (Bob), protecting against eavesdropping by Eve. Additionally, RIS-I transmits its own signals to a secondary user (SU) using backscattering radio technology. Meanwhile, RIS-II serves as a cooperative jammer, converting received confidential signals from Alice into jamming signals by strategically adjusting its reflection coefficients to disrupt Eve’s reception. These RISs can operate cooperatively; when RIS-II transmits as an STx, RIS-I functions as a cooperative jammer. We explore two scenarios: 1. With perfect CSI for the wiretap channel, we propose a joint SDR(Semi-definite relaxation)+MM(Minorization-maximization) optimization algorithm to simultaneously optimize Alice’s beamforming vector and the RISs’ reflection coefficients. 2. With imperfect CSI, we derive the secrecy outage probability formula and evaluate the scheme’s performance across different scenarios. Numerical results demonstrate that RIS-assisted cooperative jamming significantly enhances the secrecy rate and reduces the secrecy outage probability for Bob, outperforming traditional RIS-assisted SR systems.