Covert Communication and Physical Layer Security in Hybrid Power–Frequency Multiple Access With Friendly Jamming: Performance Analysis and Deep Learning Evaluation
Covert communication and physical layer security (PLS) have emerged as two essential pillars for safeguarding wireless networks against increasingly sophisticated eavesdropping and surveillance threats. This paper investigates a downlink hybrid power–frequency multiple access (HPMA) system aided by a friendly jammer, where a single source communicates with two legitimate users in the presence of a passive eavesdropper. By jointly exploiting the power and frequency domains, the proposed HPMA scheme achieves clear advantages in terms of covertness and secrecy performance compared to conventional orthogonal multiple access (OMA) and non-orthogonal multiple access (NOMA) schemes. For performance analysis, we derive closed-form and approximated expressions for key metrics, including detection error probability (DEP), secrecy outage probability (SOP), effective secrecy throughput (EST), and average secrecy capacity (ASC), which reveal important trade-offs among resource allocation, jammer power, and secrecy reliability. To further reduce the computational burden of conventional analysis, a regression-based deep neural network (DNN) framework is developed to efficiently predict the secrecy performance of the considered system. Extensive Monte Carlo simulations validate the analytical results and confirm the superiority of the proposed HPMA scheme with friendly jamming. These findings provide useful insights for the design of future secure and covert wireless systems with low-complexity and intelligent physical-layer security requirements.
Covert communication and physical layer security (PLS) have emerged as two essential pillars for safeguarding wireless networks against increasingly sophisticated eavesdropping and surveillance threats. This paper investigates a downlink hybrid power–frequency multiple access (HPMA) system aided by a friendly jammer, where a single source communicates with two legitimate users in the presence of a passive eavesdropper. By jointly exploiting the power and frequency domains, the proposed HPMA scheme achieves clear advantages in terms of covertness and secrecy performance compared to conventional orthogonal multiple access (OMA) and non-orthogonal multiple access (NOMA) schemes. For performance analysis, we derive closed-form and approximated expressions for key metrics, including detection error probability (DEP), secrecy outage probability (SOP), effective secrecy throughput (EST), and average secrecy capacity (ASC), which reveal important trade-offs among resource allocation, jammer power, and secrecy reliability. To further reduce the computational burden of conventional analysis, a regression-based deep neural network (DNN) framework is developed to efficiently predict the secrecy performance of the considered system. Extensive Monte Carlo simulations validate the analytical results and confirm the superiority of the proposed HPMA scheme with friendly jamming. These findings provide useful insights for the design of future secure and covert wireless systems with low-complexity and intelligent physical-layer security requirements.
This study analyzes the physical-layer security and covert communication in hybrid power-frequency multiple-access (PFMA) systems. By partially overlapping users’ signals in power domains coupled with orthogonal transmission, PFMA exhibits strong resistance to untrusted users exploiting information intended for a distant user in non-orthogonal multiple access (NOMA), for its ability to successive interference cancellation-free approach. In the context of internal users intercepting signals within the same power domain, external users eavesdropping on legitimate users, and external wardens monitoring communications, we derive closed-form expressions for the connection outage probability (COP), secrecy outage probability (SOP), and detection error probability (DEP). Furthermore, we establish closed-form approximations for the optimal transmitting signal-to-noise ratio and the warden’s detection threshold factors to minimize the DEP. Numerical results are studied to very demonstrate the superiority of PFMA in improving COP and SOP compared to NOMA. The study also examines the impacts of different knowledge communication channels on DEP performance.
In this article, we study the physical-layer security (PHY-security) improvement method for a downlink nonorthogonal multiple access (NOMA) system in the presence of an active eavesdropper. To this end, we propose a full-duplex (FD)-enabled NOMA system and a promising scheme, called the minimal transmitter selection (MTS) scheme, to support secure transmission. Specifically, the cell-center and cell-edge users act simultaneously as both receivers and jammers to degrade the eavesdropper channel condition. Additionally, the proposed MTS scheme opportunistically selects the transmitter to minimize the maximum eavesdropper channel capacity. To estimate the secrecy performance of the proposed methods, we derive an approximated closed-form expression for secrecy outage probability (SOP) and build a deep neural network (DNN) model for SOP evaluation. Numerical results reveal that the proposed NOMA system and MTS scheme improve not only the SOP but also the secrecy sum throughput. Furthermore, the estimated SOP through the DNN model is shown to be tightly close to other approaches, i.e., the Monte-Carlo method and analytical expressions. The advantages and drawbacks of the proposed transmitter selection scheme are highlighted, along with insightful discussions.
In this paper, we investigate the secrecy performance of an uplink-downlink power domain non-orthogonal multiple access (PD-NOMA) system with imperfect successive interference cancellation (SIC) in physical layer security (PLS). In the proposed system, two source users (SUs) communicate with two destination users (DUs) with the help of a cluster of multi-relay nodes using the decode-and-forward (DF) protocol in the presence of multi-eavesdroppers. These eavesdroppers try to overhear the wireless signal around the DUs. In our system, the selected DF-relay node also works as a jammer to improve security and protect confidential information from multi-eavesdroppers. In this role, the DF-relay node generates a jamming signal, creating artificial interference to reduce the quality of the eavesdropping channels. To evaluate the secrecy performance of the system, we derived the analytical expressions of the secrecy outage probability (SOP) for both DUs using three relay selection strategies over Rayleigh fading channels and used Monte Carlo simulations to confirm the accuracy of our calculations. Furthermore, we examined the effects of system parameters such as the number of eavesdroppers and DF relaying nodes, the power allocation, SIC performance, the position of eavesdropper on the SOP of the two DUs. We compared the performance of our proposed NOMA system with those of conventional orthogonal multiple access (OMA) schemes.
This paper investigates the physical layer security (PLS) of non-orthogonal multiple access (NOMA)-enabled overlay cognitive radio networks (NOMA-OCRNs), considering multiple non-colluding eavesdroppers. Here PLS is evaluated in terms of: (i) secrecy outage probability (SOP) of primary user (PU) and secondary user (SU) and (ii) system SOP (SSOP), system secrecy throughput (SST) and secrecy energy efficiency (SEE) of the network. Residual hardware impairments arising from non-ideal hardware and imperfect successive interference cancellation conditions are considered. Firstly, we derive new analytical expressions for the SOPs of PU and SU. Numerical evaluation results show that both PU as well as SU suffer very high SOPs that tend to unity in the high transmit power region. Further, RHI and i-SIC have a significant impact on the secrecy performance. To improve the PLS performance, we propose a jamming-assisted framework and develop novel analytical models for determining the SOPs of PU and SU. We derive the asymptotic SOP expressions as well. Detailed analytical and simulation results are presented to demonstrate that the proposed jamming-assisted framework leads to a significant reduction of the SOPs of both PU and SU while exhibiting considerable enhancement of SST and SEE of the network compared to the no-jammer scenario. In the final part of this paper, we utilize a deep learning framework for the precise and fast prediction of the SOPs of PU and SU, that can replace complex mathematical modeling.
NOMA (Non-Orthogonal Multiple Access) has been recognized as new multiple access technology for wireless communication networks of the fifth generation and beyond, owing to its ability to improve spectral efficiency, support massive connectivity, and provide user fairness. However, it has been observed that the superposition-based transmission principle of NOMA is highly susceptible to eavesdropping attacks, especially in an open wireless network where all wireless communications are inherently broadcast in nature. Hence, ensuring secure wireless communications for NOMA systems has now become an important area of research. This research aims to improve the secrecy level of wireless communications for NOMA systems by employing Physical Layer Security (PLS) techniques. Specifically, two prominent PLS techniques, Artificial Noise (AN) and Cooperative Jamming (CJ), have been employed to provide security against passive eavesdropping attacks. The cooperative NOMA system architecture is considered, and the secrecy enhancement is analyzed for two possible scenarios when the eavesdropper is close to the relay node and when the eavesdropper is close to the base station. The secrecy performance of the proposed system is analyzed through various parameters, namely, Secrecy Outage Probability (SOP), Secrecy Capacity (SC), Secrecy Rate (SR), and Secrecy Energy Efficiency (SEE) in terms of the Signal to Noise Ratio (SNR). The numerical results for the secrecy metrics are obtained through MATLAB-based simulations, whereas the system-level model is developed using the Simulink platform to verify the suggested system's functionality in the presence of AN and CJ for the legitimate NOMA users and the eavesdropper. The results show that the secrecy performance is significantly enhanced with the introduction of AN and CJ, and the system shows robust performance in terms of energy efficiency. This paper provides significant insights into the design of the NOMA system from the secrecy perspective and validates the potential of PLS techniques for the design of the future wireless system.
This paper studies the secure communications of a wireless-powered full-duplex cooperative non-orthogonal multiple access (CoNOMA) system with a source node, a group of near users, a far user and an external eavesdropper. In particular, the eavesdropper intends to wiretap the transmitted signals from the source. Two of the near users are picked up, served as a wireless-powered relay and a wireless friendly jammer, respectively. We propose a user selection and cooperative jamming based secure transmission scheme. Specifically, the source transmits a superimposed signal to the selected near user. The selected near user, who is employed as a relay, can harvest energy from the radio frequency signals and decode the information simultaneously. The harvested energy are then utilized to forward the signal to the far user. The jammer also collects energy from the source, and emits artificial noise by using the harvested energy to confuse the eavesdropper. Based on the proposed scheme, the closed-form expression for secrecy outage probability (SOP) and effective secrecy throughput (EST) are derived. The correctness of our theoretical analysis is verified by Monte-Carlo simulations, and the superiority of the proposed scheme in improving the system secure performance is also validated.