In this paper, we examine the effectiveness of distributed null-steering-based physical layer security (PLS) in over-the-air computation (AirComp), considering the impact of imperfect channel estimation. AirComp has been extensively studied for its ability to efficiently aggregate data in Internet of Things (IoT) networks, but dealing with imperfect channel estimation is a major pragmatic challenge in these networks. This work focuses on how phase errors in imperfect channel estimation affect AirComp’s distributed null-steering-based PLS by evaluating their impact on the mean square error (MSE) performance. A closed-form expression is derived to quantify the degradation in PLS performance of AirComp systems caused by channel estimation errors. The analysis shows that imperfect channel state information (CSI) causes a non-negligible degradation in the MSE performance and also reduces the effectiveness of the PLS technique employed. The degradation of up to 10 times in the average MSE received at the desired location is observed at the loop SNR value of 5 dB. Furthermore, the average MSE gap between the legitimate receiver and the eavesdropper is reduced by more than 0.1 with imperfect channel estimation. The results provide insights into the potential degradation due to imperfect CSI, which helps to quantify the relationship between the CSI estimation error and its impact on the PLS performance of AirComp networks.
In this paper, we examine the effectiveness of distributed null-steering-based physical layer security (PLS) in over-the-air computation (AirComp), considering the impact of imperfect channel estimation. AirComp has been extensively studied for its ability to efficiently aggregate data in Internet of Things (IoT) networks, but dealing with imperfect channel estimation is a major pragmatic challenge in these networks. This work focuses on how phase errors in imperfect channel estimation affect AirComp’s distributed null-steering-based PLS by evaluating their impact on the mean square error (MSE) performance. A closed-form expression is derived to quantify the degradation in PLS performance of AirComp systems caused by channel estimation errors. The analysis shows that imperfect channel state information (CSI) causes a non-negligible degradation in the MSE performance and also reduces the effectiveness of the PLS technique employed. The degradation of up to 10 times in the average MSE received at the desired location is observed at the loop SNR value of 5 dB. Furthermore, the average MSE gap between the legitimate receiver and the eavesdropper is reduced by more than 0.1 with imperfect channel estimation. The results provide insights into the potential degradation due to imperfect CSI, which helps to quantify the relationship between the CSI estimation error and its impact on the PLS performance of AirComp networks.
With the rapid proliferation of the Internet of Things (IoT), small devices in various applications generate, process, and exchange security and safety-critical data as well as privacy-sensitive information. However, due to limited hardware capabilities of such small devices, the IoT networks are inherently vulnerable to security attacks. In this context, the analog cooperative beamforming (ACB)-based physical layer security (PLS) technique can be a suitable solution to guarantee security in the IoT networks by creating a virtual antenna array with multiple IoT devices. Nevertheless, such techniques suffer from poor secrecy performance, when an eavesdropper is located within the main beam toward the legitimate receiver. Motivated by this limitation, in this article, we propose a fully distributed null-steering beamformer, which is suitable for IoT networks following decentralized architecture. Through analysis and simulation, we show that the proposed PLS algorithm outperforms the existing ACB-based PLS scheme. Furthermore, we show that there exists an optimal degree of nulling that maximizes the secrecy performance, which can be estimated based on the analytical results.
In recent years, physical layer security (PLS) has emerged as a promising concept to complement cryptography solutions. Many PLS schemes require perfect knowledge of the channel state information (CSI) at the transmitter. However, in practical cases, CSI is often imperfect due to channel estimation errors, noisy feedback channels and outdated CSI. In this paper, we study the impact of imperfect CSI on an adaptive PLS scheme that combines diversity with interleaving to provide security. Particularly, we derive the secrecy capacity expressions for the legitimate receiver and the eavesdropper's channels under imperfect CSI conditions. Numerical and theoretical simulations for secrecy capacity and bit error rate (BER) are carried out for the frequency-selective Rayleigh fading wiretap channel model. The results reveal the negative impact of imperfect CSI on the secrecy and BER performance of the single input single output (SISO) orthogonal frequency division multiplexing (OFDM) system. The analysis is done under both frequency division duplex (FDD) and time division duplex (TDD) modes.
Physical layer security (PLS) is an emerging paradigm that makes use of wireless channel characteristics to provide security. Many PLS schemes require knowledge of the channel state information (CSI). However, CSI is usually imperfect due to factors such as noisy feedback channels, channel estimation errors and outdated CSI. In this paper, we investigate the impact of imperfect CSI on the secrecy and error rate performances of a PLS scheme that combines adaptive matched-filter (MF) precoding and diversity in orthogonal frequency division multiplexing (OFDM). Particularly, we derive the secrecy capacity and error rate expressions for the legitimate and eavesdropper's channels under imperfect CSI assumption. The impact of the imperfect CSI is studied via theoretical as well as numerical techniques in frequency-selective Rayleigh fading wiretap channel. The analysis is done in both frequency division duplex (FDD) and time division duplex (TDD) modes.
Although underwater wireless optical communication (UWOC) receives much interest lately, security issues associated with it get little attention. In this work, it is the first attempt to investigate the physical layer security (PLS) performance of the vertical UWOC system with perfect and imperfect channel state information (CSI). Specifically speaking, the communication between two legitimate peers in the presence of an external eavesdropper is studied from the information-theoretic security perspective. Assuming that turbulence-induced fading over the vertical UWOC links is respectively subject to cascaded lognormal (LN) and Gamma-Gamma (GG) distributions for weak and moderate/strong turbulence conditions, and the angular pointing error is randomized by the Beckmann distribution, the composite cascaded statistical fading models are derived with the comprehensive effects of path loss, underwater turbulence, angular pointing errors, and channel estimation error. On the basis of these models, analysis frameworks of the probability of strictly positive secrecy capacity (SPSC), secrecy outage probability (SOP), and average secrecy capacity (ASC) are further obtained for this UWOC system, which are confirmed by Monte Carlo (MC) simulations. Furthermore, the effects including the number of layers, the level of channel estimation error, the link distance, the location of the eavesdropper, the quality of the main and eavesdropping channels on this system are analyzed for different water conditions. The presented results give valuable insights into the practical aspects of deployment of UWOC networks.
In recent years, physical layer security has been regarded as a promising technique to facilitate secure communications in next generation mobile systems, where theoretically massive MIMO can significantly enhance the system secrecy performance under its advantage in shaping the transmitted signals to null the interference or leakage. However, in practical systems, the achievable secrecy performance under imperfect channel state information (CSI) deserves further investigation. In this paper, we give a detailed analysis about the physical layer security problem in a multi-user massive MIMO system with imperfect CSI. The considered imperfect CSI includes both the outdated CSI due to the transmission and processing delay, and the channel estimation error. We first derive a tight asymptotic lower bound of the ergodic system secrecy capacity under imperfect CSI, and then analyze how imperfect CSI affects the system secrecy performance. Moreover, we propose a channel prediction scheme that can result in more accurate CSI, in order to alleviate the negative effect on the achievable system secrecy capacity caused by imperfect CSI. Simulation results reveal that the imperfect CSI greatly reduces the system secrecy capacity, while our designed channel prediction scheme can effectively mitigate the harmful impact of imperfect CSI and thus improve the system secrecy performance.
This paper investigates physical layer security in multi-antenna keyhole systems with imperfect channel state information (CSI). In dense urban environments, rank-deficient channels, specifically the rank-one keyhole effect, significantly degrade secrecy performance. We derive closed-form asymptotic expressions for the secrecy outage probability (SOP) and average secrecy rate (ASR) in the high signal-to-noise ratio (SNR) regime. Based on the analytical results and Monte-Carlo simulations, the impacts of key parameters, such as Alice's antenna number and CSI error variance, are quantified and discussed, which provides insights into robust secrecy design.