This letter investigates the use of pilot-based codebook artificial noise (PCAN) in Integrated Sensing and Communication (ISAC) systems to enhance physical layer security. ISAC technology integrates communication and sensing through shared resources, emphasizing the need for secure strategies. PCAN allows the receiver to extract information from the pilot codebook, effectively removing interference and increasing secrecy capacity. The non-convex secrecy capacity optimization problem is addressed by decomposing it into simpler subproblems. A semidefinite relaxation (SDR) and alternating optimization algorithm is proposed to maximize secrecy capacity while maintaining sensing accuracy. Simulation results show significant improvements, particularly at low and moderate Signal-to-Noise Ratio (SNR), with consistent gains at high SNRs. This work underscores the role of optimization techniques in enhancing secure communication and balancing secrecy with sensing performance in ISAC systems.
This letter investigates the use of pilot-based codebook artificial noise (PCAN) in Integrated Sensing and Communication (ISAC) systems to enhance physical layer security. ISAC technology integrates communication and sensing through shared resources, emphasizing the need for secure strategies. PCAN allows the receiver to extract information from the pilot codebook, effectively removing interference and increasing secrecy capacity. The non-convex secrecy capacity optimization problem is addressed by decomposing it into simpler subproblems. A semidefinite relaxation (SDR) and alternating optimization algorithm is proposed to maximize secrecy capacity while maintaining sensing accuracy. Simulation results show significant improvements, particularly at low and moderate Signal-to-Noise Ratio (SNR), with consistent gains at high SNRs. This work underscores the role of optimization techniques in enhancing secure communication and balancing secrecy with sensing performance in ISAC systems.
Pilot-Based Codebook Artificial Noise (PCAN), which plays a crucial role in ensuring secure communication, is an emerging physical layer security technique. PCAN faces a significant challenge due to the unknown eavesdropper channel. To address this issue, this letter re-models the eavesdropper channel using random matrix theory. By applying the$\eta $-transform and Shannon-transform, the asymptotic expression for the eavesdropper channel capacity is derived under the condition of an unknown eavesdropper channel. The simulation result shows that when the number of transmitter antennas equals the number of eavesdropper antennas and the system dimension is large, the model can effectively characterize the eavesdropper channel capacity. Within this framework, the secrecy capacity is optimized using the Difference of Convex functions - Successive Convex Approximation (DC-SCA) algorithm, providing a new approach to improve the performance of PCAN.
Non-Orthogonal Artificial Noise (NORAN) has garnered significant attention in modern communication systems as a substitute for traditional Artificial Noise (AN), due to its independence from channel degrees of freedom. However, the design of NORAN leads to a reduction in the channel capacity of legitimate channels, thereby limiting its application in practical systems. Pilot-based Codebook Non-Orthogonal Artificial Noise (PCAN) leverages pilot signals exchanged between the receiver and transmitter as encryption keys. This allows the receiver to retrieve the upcoming PCAN from the codebook via the pilot signals, effectively transitioning from NORAN to AN in form, demonstrating high adaptability. Consequently, this paper investigates the deployment of PCAN in Massive MIMO systems to achieve secure communication. Considering the eavesdropper as an illegitimate user, whose channel state information matrix is unknown to the legitimate receiver and does not follow a simple distribution pattern, this study employs random matrix theory to model the channel of an unknown eavesdropper. It uses the successive convex approximation algorithm to analyze the optimal power allocation strategy and the maximum number of eavesdropper antennas that the system can tolerate under these conditions. The findings indicate that as the number of eavesdropper antennas increases, the eavesdropper channel modeling based on random matrix theory increasingly approximates the actual channel characteristics of the eavesdropper. Notably, when the number of eavesdropper antennasNE=128, the consistency between the modeled channel and the actual channel reaches 87.2%, and the optimal power allocation factor at this point isθ=0.5. However, as the number of eavesdropper antennas continues to increase, the effectiveness of PCAN becomes more pronounced. Nevertheless, when the number of eavesdropper antennas approaches infinity, the efficacy of PCAN significantly decreases, failing to adequately ensure the system’s security.
Contemporary research has highlighted that the design possibilities for Orthogonal Artificial Noise (AN) are circumscribed by the inherent limitations in channel degrees of freedom, yielding a scant assortment of design alternatives. In this letter, Non-Orthogonal Artificial Noise (NORAN) emerges as a viable substitute. Its applications have been recognized in relay communication systems such as those involving Unmanned Aerial Vehicles (UAVs) and Intelligent Reflecting Surfaces (IRS). Despite this, the mathematical exploration of the Secrecy Capacity (SC) function within wireless communication systems incorporating NORAN has been scant. This letter pioneers the examination of the concave-convex nature of the SC function in such systems. The findings reveal that, subject to certain transmit power conditions, the SC function for NORAN is inherently convex, implying a decrement in SC upon NORAN’s deployment, which negates its intended effect. In response to this conundrum, this discourse introduces Pilot-based Codebook Non-Orthogonal Artificial Noise (PCAN), wherein the codebook capitalizes on pilot signals exchanged between the receiver and sender as an encryption key. The receiver, with the aid of the pilot signals, retrieves the forthcoming PCAN from the codebook, thereby neutralizing the PCAN’s influence during the reception of information. This innovation equates the SC functions of PCAN and AN within the same channel framework. Additionally, this study delves into the optimization conundrum of PCAN, considering scenarios of both perfect and imperfect Channel State Information (CSI). Through theoretical analysis, it is established that with an ideal CSI and an signal-to-noise ratio (SNR) surpassing zero, the quintessential power allocation for PCAN equates to half of the total transmission power. Contrariwise, under imperfect CSI parameters, PCAN fails to deliver efficacy.
In recent research, non-orthogonal artificial noise (NORAN) has been proposed as an alternative to orthogonal artificial noise (AN). However, NORAN introduces additional noise into the channel, which reduces the capacity of the legitimate channel (LC). At the same time, selecting a NORAN design with ideal security performance from a large number of design options is also a challenging problem. To address these two issues, a novel NORAN based on a pilot information codebook is proposed in this letter. The codebook associates different suboptimal NORANs with pilot information as the key under different channel state information (CSI). The receiver interrogates the codebook using the pilot information to obtain the NORAN that the transmitter will transmit in the next moment, in order to eliminate the NORAN when receiving information. Therefore, NORAN based on pilot information codebooks can improve the secrecy capacity (SC) of the communication system by directly using suboptimal NORAN design schemes without increasing the noise in the LC. Numerical simulations and analyses show that the introduction of NORAN with a novel design using pilot information codebooks significantly enhances the security and improves the SC of the communication system.
Integrated Sensing and Communication (ISAC) can reuse the same spectrum and hardware resources for communication and radar sensing, which is a promising technology to alleviate spectrum congestion. Recently, there has been an increasing research interest in the physical layer secrecy aspects of ISAC systems. This paper studies a basic multiple-input single-output ISAC secrecy system, where a multi-antenna base station transmits a unified signal to sense a point target and communicate to a single-antenna receiver in the presence ofKsingle antenna eavesdroppers. Under this setup, a sensing signal-to-noise ratio (SNR) constrained secrecy rate maximization problem has been formulated. We showed that the problem can be reformulated as a convex semidefinite programming problem and proved that beamforming is the optimal transmission scheme. We derived two low-complexity semiclosed-form optimal beamforming solutions and one suboptimal closed-form solution. Numerical results demonstrate that the proposed solutions attain the optimum of the sensing SNR constrained secrecy rate maximization problem and have lower computational complexity than the existing method.
Empowered by the integrated sensing and communication capability, this paper proposes a new two-stage artificial noise (AN)-assisted secure beamforming design towards physical layer security enhancement. Specifically, in the first stage a nearly omni-directional AN is used for sensing the eavesdropper, where the AN is radiated istropically except in the direction of the communication user. With the known channel knowledge of the eavesdropper, a spatially AN is transmitted in the second stage to deliberately degrade the eavesdropper. To balance the sensing and secure communication performance, we aim to maximize the effective secrecy rate by jointly optimize the time allocation and the transmit beamforming in both stages. A efficient optimization algorithm based on weighted minimum mean square error is then developed to solve the formulated non-convex problem. Simulation results are provided to demonstrate the performance advantage of our proposed design over the existing benchmark schemes in terms of achieving a larger effective secrecy rate.