Hardware Impaired Ambient Backscatter NOMA Systems: Reliability and Security

Abstract: Non-orthogonal multiple access (NOMA) and ambient backscatter communication have been envisioned as two promising technologies for the Internet-of-things due to their high spectral efficiency and energy efficiency. Motivated by this fact, we consider an ambient backscatter NOMA system in the presence of a malicious eavesdropper. Under some realistic assumptions of residual hardware impairments (RHIs), channel estimation errors (CEEs) and imperfect successive interference cancellation (ipSIC), we investigate the physical layer security (PLS) of the ambient backscatter NOMA systems focusing on reliability and security. In order to further improve the security of the considered system, an artificial noise scheme is proposed where the radio frequency (RF) source acts as a jammer that transmits interference signal to the legitimate receivers and eavesdropper. On this basis, the analytical expressions for the outage probability (OP) and the intercept probability (IP) are derived. To gain more insights, the asymptotic analysis and diversity orders for the OP in the high signal-to-noise ratio (SNR) regime are carried out, and the asymptotic behaviors of the IP in the high main-to-eavesdropper ratio (MER) region are explored as well. Numerical results show that: 1) RHIs, CEEs and ipSIC have negative effects on the OP but positive effects on the IP; 2) Compared with CEEs, RHIs have a more serious impact on the reliability and security of the considered system; 3) There exists a trade-off between reliability and security, and this trade-off can be optimized by reducing the power coefficient of the artificial noise or increasing the interfering factor of readers; 4) There are error floors for the OP due to the CEEs and the reflection coefficient; 5) As MER grows large, the security for Rnand Rf is improved, while the security for T is reduced.

• The paper analyzes the reliability and physical layer security of ambient backscatter NOMA systems under residual hardware impairments, channel estimation errors, and imperfect SIC, proposing an artificial noise scheme.
• Key findings reveal that hardware impairments, especially RHIs, negatively affect reliability (OP) but improve security (IP), indicating a complex trade-off.
• The study shows that optimizing this reliability-security trade-off is possible by adjusting parameters like artificial noise power or reader interference factors, while warning of error floors in reliability at high SNR and nuanced security effects on different devices based on MER.

Analysis of Reliability and Security in Hardware-Impaired Ambient Backscatter NOMA Systems

The paper "Hardware Impaired Ambient Backscatter NOMA Systems: Reliability and Security" explores the reliability and security of ambient backscatter communication systems integrated with Non-Orthogonal Multiple Access (NOMA) under hardware impairments. The study is significant in the context of the Internet-of-Things (IoT), where enhancing spectral and energy efficiency is paramount.

Core Contributions

The research focuses on the physical layer security (PLS) of ambient backscatter NOMA systems while addressing residual hardware impairments (RHIs), channel estimation errors (CEEs), and imperfect successive interference cancellation (ipSIC). The authors propose an artificial noise scheme to protect the system from malicious eavesdroppers, where the radio frequency (RF) source disrupts unauthorized reception with interference signals.

The paper provides analytical expressions for outage probability (OP) and intercept probability (IP), accompanied by an asymptotic analysis of OP in the high signal-to-noise ratio (SNR) regime, and IP in the high main-to-eavesdropper ratio (MER) scenario. Several key findings are reported:

1. Impact of Impairments: RHIs, CEEs, and ipSIC exhibit negative effects on OP but beneficial impacts on IP, pointing to an intricate reliability-security trade-off.
2. Dominance of RHIs: Among the examined impairments, RHIs have a disproportionately more severe impact on system performance.
3. Trade-off Management: The reliability-security equilibrium can be optimized by adjusting the power coefficient of artificial noise or the interference factor of readers.
4. Error Floors: Due to CEEs and reflection coefficient factors, OP displays error floors in high SNR conditions.
5. MER Effects: As MER grows larger, security improves for the far and near readers, while it diminishes for the tag.

Theoretical and Practical Implications

The implications of the study are twofold. Theoretically, the results deepen the understanding of non-ideal factors affecting ambient backscatter NOMA systems, allowing for the enhancement of design strategies focusing on security and reliability. Practically, this research informs the deployment of IoT systems by providing solutions to mitigate the vulnerabilities introduced by RHIs, CEEs, and ipSIC, thereby contributing to the secure and efficient expansion of IoT networks.

Future Prospects

The insights from this paper present several avenues for future research and development in secure IoT systems. Notably, the interplay of impairments with advanced interference management techniques could further enrich the system’s reliability and security. Additionally, adopting deep learning approaches for real-time adjustment of system parameters might lead to novel solutions against both RHIs and CEEs, fostering the emergence of highly adaptive, secure ambient backscatter communication systems.

In conclusion, the paper provides a comprehensive analysis of hardware-impacted ambient backscatter NOMA systems, emphasizing essential methodologies for achieving robust communication in the growing domain of IoT networks.