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Physical Layer Security in AmBC-NOMA Networks with Random Eavesdroppers

Xinyue Pei, Xingwei Wang, Min Huang, Yingyang Chen, Xiaofan Li, Theodoros A. Tsiftsis

TL;DR

This work addresses physical layer security in AmBC-NOMA networks with randomly distributed eavesdroppers modeled by a homogeneous Poisson point process. By combining artificial noise (AN) injection at the base station with an Eve-exclusion protection zone, the authors derive closed-form outage probability and intercept probability expressions for the near user, far user, and backscatter device, including high-SNR asymptotics that reveal OP floors and zero diversity. The analysis leverages stochastic geometry and specialized functions (e.g., the exponential-integral function) to capture the impact of random Eves and backscatter interference, and it validates results with extensive numerical simulations. The findings demonstrate that AN and the protected zone effectively enhance PLS, and the work provides deep insights into how system parameters (transmit SNR, reflection efficiency, power allocation, exclusion radius, Eve density, and backscattered AN cancellation) shape reliability and security in AmBC-NOMA deployments.

Abstract

In this work, we investigate the physical layer security (PLS) of ambient backscatter communication non-orthogonal multiple access (AmBC-NOMA) networks where non-colluding eavesdroppers (Eves) are randomly distributed. In the proposed system, a base station (BS) transmits a superimposed signal to a typical NOMA user pair, while a backscatter device~(BD) simultaneously transmits its unique signal by reflecting and modulating the BS's signal. Meanwhile, Eves passively attempt to wiretap the ongoing transmissions. Notably, the number and locations of Eves are unknown, posing a substantial security threat to the system. To address this challenge, the BS injects artificial noise (AN) to mislead the Eves, and a protected zone is employed to create an Eve-exclusion area around the BS. Theoretical expressions for outage probability (OP) and intercept probability (IP) are provided to evaluate the system's reliability-security trade-off. Asymptotic behavior at high signal-to-noise ratio (SNR) is further explored, including the derivation of diversity orders for the OP. Numerical results validate the analytical findings through extensive simulations, demonstrating that both the AN injection and protected zone can effectively enhance PLS. Furthermore, analysis and insights of different key parameters, including transmit SNR, reflection efficiency at the BD, power allocation coefficient, power fraction allocated to desired signal, Eve-exclusion area radius, Eve distribution density, and backscattered AN cancellation efficiency, on OP and IP are also provided.

Physical Layer Security in AmBC-NOMA Networks with Random Eavesdroppers

TL;DR

This work addresses physical layer security in AmBC-NOMA networks with randomly distributed eavesdroppers modeled by a homogeneous Poisson point process. By combining artificial noise (AN) injection at the base station with an Eve-exclusion protection zone, the authors derive closed-form outage probability and intercept probability expressions for the near user, far user, and backscatter device, including high-SNR asymptotics that reveal OP floors and zero diversity. The analysis leverages stochastic geometry and specialized functions (e.g., the exponential-integral function) to capture the impact of random Eves and backscatter interference, and it validates results with extensive numerical simulations. The findings demonstrate that AN and the protected zone effectively enhance PLS, and the work provides deep insights into how system parameters (transmit SNR, reflection efficiency, power allocation, exclusion radius, Eve density, and backscattered AN cancellation) shape reliability and security in AmBC-NOMA deployments.

Abstract

In this work, we investigate the physical layer security (PLS) of ambient backscatter communication non-orthogonal multiple access (AmBC-NOMA) networks where non-colluding eavesdroppers (Eves) are randomly distributed. In the proposed system, a base station (BS) transmits a superimposed signal to a typical NOMA user pair, while a backscatter device~(BD) simultaneously transmits its unique signal by reflecting and modulating the BS's signal. Meanwhile, Eves passively attempt to wiretap the ongoing transmissions. Notably, the number and locations of Eves are unknown, posing a substantial security threat to the system. To address this challenge, the BS injects artificial noise (AN) to mislead the Eves, and a protected zone is employed to create an Eve-exclusion area around the BS. Theoretical expressions for outage probability (OP) and intercept probability (IP) are provided to evaluate the system's reliability-security trade-off. Asymptotic behavior at high signal-to-noise ratio (SNR) is further explored, including the derivation of diversity orders for the OP. Numerical results validate the analytical findings through extensive simulations, demonstrating that both the AN injection and protected zone can effectively enhance PLS. Furthermore, analysis and insights of different key parameters, including transmit SNR, reflection efficiency at the BD, power allocation coefficient, power fraction allocated to desired signal, Eve-exclusion area radius, Eve distribution density, and backscattered AN cancellation efficiency, on OP and IP are also provided.

Paper Structure

This paper contains 29 sections, 14 theorems, 61 equations, 7 figures, 3 tables.

Table of Contents

  1. Introduction
  2. Related Works
  3. PLS design in AmBC network
  4. PLS design in AmBC-NOMA
  5. Motivations and Contributions
  6. Motivations and Novelty
  7. Contributions
  8. Outline and Notations
  9. System Model
  10. System Overview
  11. Transmission Model
  12. Signal Decoding Process
  13. Outage Probability Analysis
  14. OP of $U_F$
  15. OP of $U_N$
  16. ...and 14 more sections

Key Result

Theorem 1

The OP of $U_F$ can be derived as where $\mathcal{A}_0$ and $\mathcal{B}_0$ have been defined in Table OP_parameters.

Figures (7)

  • Figure 1: System model.
  • Figure 2: OP and IP versus transmit SNR.
  • Figure 3: OP and IP versus reflection efficiency.
  • Figure 4: OP versus power allocation coefficient $a_N$ and power fraction $\theta$.
  • Figure 5: IP versus power allocation coefficient $a_N$ and power fraction $\theta$.
  • ...and 2 more figures

Theorems & Definitions (27)

  • Theorem 1
  • proof
  • Theorem 2
  • proof
  • Theorem 3
  • proof
  • Corollary 1
  • proof
  • Corollary 2
  • Corollary 3
  • ...and 17 more