Logo
ScienceStack
Table of Contents
Fetching ...
Sign In

AmbShield: Enhancing Physical Layer Security with Ambient Backscatter Devices against Eavesdroppers

Yifan Zhang, Yishan Yang, Riku Jäntti, Zheng Yan, Dusit Niyato, Zhu Han

TL;DR

AmbShield tackles passive eavesdropping in wireless networks by leveraging ambient backscatter devices (AmBDs) to simultaneously strengthen the legitimate channel and interfere with the eavesdropper without additional transmit power. The authors develop a unified analytical framework to derive the exact PDFs/CDFs of the legitimate and eavesdropper SINRs and a closed-form secrecy outage probability (SOP) in Fox–$H$ form, along with high-SNR asymptotics and a secrecy diversity order of $1$. They validate the theory with Monte Carlo simulations and show SOPs below $10^{-3}$ under practical conditions, even with imperfect synchronization and CSI estimation, demonstrating the practical viability of AmBD-assisted PLS. The work provides concrete design guidelines for deploying AmBDs to enhance physical-layer security in real-world networks.

Abstract

Passive eavesdropping compromises confidentiality in wireless networks, especially in resource-constrained environments where heavyweight cryptography is impractical. Physical layer security (PLS) exploits channel randomness and spatial selectivity to confine information to an intended receiver with modest overhead. However, typical PLS techniques, such as using beamforming, artificial noise, and reconfigurable intelligent surfaces, often involve added active power or specialized deployment, and, in many designs, rely on precise time synchronization and perfect CSI estimation, which limits their practicality. To this end, we propose AmbShield, an AmBD-assisted PLS scheme that leverages naturally distributed AmBDs to simultaneously strengthen the legitimate channel and degrade eavesdroppers' without requiring extra transmit power and with minimal deployment overhead. In AmbShield, AmBDs are exploited as friendly jammers that randomly backscatter to create interference at eavesdroppers, and as passive relays that backscatter the desired signal to enhance the capacity of legitimate devices. We further develop a unified analytical framework that analyzes the exact probability density function (PDF) and cumulative distribution function (CDF) of legitimate and eavesdropper signal-to-interference-noise ratio (SINR), and a closed-form secrecy outage probability (SOP). The analysis provides clear design guidelines on various practical system parameters to minimize SOP. Extensive experiments that include Monte Carlo simulations, theoretical derivations, and high-SNR asymptotic analysis demonstrate the security gains of AmbShield across diverse system parameters under imperfect synchronization and CSI estimation.

AmbShield: Enhancing Physical Layer Security with Ambient Backscatter Devices against Eavesdroppers

TL;DR

AmbShield tackles passive eavesdropping in wireless networks by leveraging ambient backscatter devices (AmBDs) to simultaneously strengthen the legitimate channel and interfere with the eavesdropper without additional transmit power. The authors develop a unified analytical framework to derive the exact PDFs/CDFs of the legitimate and eavesdropper SINRs and a closed-form secrecy outage probability (SOP) in Fox– form, along with high-SNR asymptotics and a secrecy diversity order of . They validate the theory with Monte Carlo simulations and show SOPs below under practical conditions, even with imperfect synchronization and CSI estimation, demonstrating the practical viability of AmBD-assisted PLS. The work provides concrete design guidelines for deploying AmBDs to enhance physical-layer security in real-world networks.

Abstract

Passive eavesdropping compromises confidentiality in wireless networks, especially in resource-constrained environments where heavyweight cryptography is impractical. Physical layer security (PLS) exploits channel randomness and spatial selectivity to confine information to an intended receiver with modest overhead. However, typical PLS techniques, such as using beamforming, artificial noise, and reconfigurable intelligent surfaces, often involve added active power or specialized deployment, and, in many designs, rely on precise time synchronization and perfect CSI estimation, which limits their practicality. To this end, we propose AmbShield, an AmBD-assisted PLS scheme that leverages naturally distributed AmBDs to simultaneously strengthen the legitimate channel and degrade eavesdroppers' without requiring extra transmit power and with minimal deployment overhead. In AmbShield, AmBDs are exploited as friendly jammers that randomly backscatter to create interference at eavesdroppers, and as passive relays that backscatter the desired signal to enhance the capacity of legitimate devices. We further develop a unified analytical framework that analyzes the exact probability density function (PDF) and cumulative distribution function (CDF) of legitimate and eavesdropper signal-to-interference-noise ratio (SINR), and a closed-form secrecy outage probability (SOP). The analysis provides clear design guidelines on various practical system parameters to minimize SOP. Extensive experiments that include Monte Carlo simulations, theoretical derivations, and high-SNR asymptotic analysis demonstrate the security gains of AmbShield across diverse system parameters under imperfect synchronization and CSI estimation.
Paper Structure (27 sections, 3 theorems, 78 equations, 8 figures, 2 tables)

This paper contains 27 sections, 3 theorems, 78 equations, 8 figures, 2 tables.

Table of Contents

  1. Introduction
  2. Related Work
  3. AN-based PLS Schemes
  4. Beamforming-based PLS schemes
  5. RIS-based PLS schemes
  6. AmBD-related PLS schemes
  7. System Model
  8. Channel Model
  9. Receiver Model
  10. Design Goals
  11. Performance Analysis
  12. PDF and CDF of AmbShield
  13. Legitimate Channel
  14. Eavesdropping Channel
  15. Closed-form Secrecy Outage Probability
  16. ...and 12 more sections

Key Result

Theorem 1

The Fox-H SOP for the AmbShield is where $A_{r} = \frac{\sigma_{r}^{2} \Omega_{t,r}^{ K-1}}{P\prod_{k=1}^{K}\beta_{k}}, c = \Theta - 1, d = \frac{\Theta}{c}, \lambda = \frac{1}{P \Omega_{t,e}}, \mathcal{A} = [(0,1)^{K}, (0,\tfrac{1}{2})^{K}, (0,1), (1,1)]$.

Figures (8)

  • Figure 1: System model of AmbShield, where AmBDs are leveraged as friendly jammers that randomly reflect signals to simultaneously enhance communication performance and jam eavesdroppers.
  • Figure 2: The CDF of the received SNRs at the legitimate receiver and the Eve, respectively.
  • Figure 3: The SOP versus SNR of legitimate Channel under different BD numbers
  • Figure 4: The SOP versus SNR of legitimate Channel under different $\bar{\gamma}_e$
  • Figure 5: The SOP versus SNR of legitimate Channel under different $d_{k,r}$
  • ...and 3 more figures

Theorems & Definitions (6)

  • Theorem 1
  • proof
  • Theorem 2
  • proof
  • Theorem 3
  • proof