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Intelligent Reflecting Surface-Assisted Symbiotic Radio Systems: A Double-Reflection Covert Communication Design

Yunpeng Feng, Jian Chen, Lu Lv, Yuchen Zhou, Long Yang, Naofal Al-Dhahir, Fumiyuki Adachi

TL;DR

This work derives an analytical expression for the average detection error probability of W and designs an optimal strategy to determine the transmit power and backscatter reflection coefficient and develops the phase alignment pursuit and the power leakage minimization algorithms for the PSR and the CSR cases, respectively.

Abstract

We investigate covert communication in an intelligent reflecting surface (IRS)-assisted symbiotic radio (SR) system under the parasitic SR (PSR) and the commensal SR (CSR) cases, where an IRS is exploited to create a double reflection link for legitimate users and degrade the detection performance of the warden (W). Specifically, we derive an analytical expression for the average detection error probability of W and design an optimal strategy to determine the transmit power and backscatter reflection coefficient. To further enhance the covert performance, the joint optimization of the source transmit power, backscatter device (BD) reflection coefficient, and IRS phase-shifter is formulated as an expectation-based quadratic-fractional (EQF) problem. By reformulating the original problem into a fraction-eliminated backscatter power leakage minimization problem, we further develop the phase alignment pursuit and the power leakage minimization algorithms for the PSR and the CSR cases, respectively. Numerical results confirm the accuracy of the derived results and the superiority of our proposed strategy in terms of covertness.

Intelligent Reflecting Surface-Assisted Symbiotic Radio Systems: A Double-Reflection Covert Communication Design

TL;DR

This work derives an analytical expression for the average detection error probability of W and designs an optimal strategy to determine the transmit power and backscatter reflection coefficient and develops the phase alignment pursuit and the power leakage minimization algorithms for the PSR and the CSR cases, respectively.

Abstract

We investigate covert communication in an intelligent reflecting surface (IRS)-assisted symbiotic radio (SR) system under the parasitic SR (PSR) and the commensal SR (CSR) cases, where an IRS is exploited to create a double reflection link for legitimate users and degrade the detection performance of the warden (W). Specifically, we derive an analytical expression for the average detection error probability of W and design an optimal strategy to determine the transmit power and backscatter reflection coefficient. To further enhance the covert performance, the joint optimization of the source transmit power, backscatter device (BD) reflection coefficient, and IRS phase-shifter is formulated as an expectation-based quadratic-fractional (EQF) problem. By reformulating the original problem into a fraction-eliminated backscatter power leakage minimization problem, we further develop the phase alignment pursuit and the power leakage minimization algorithms for the PSR and the CSR cases, respectively. Numerical results confirm the accuracy of the derived results and the superiority of our proposed strategy in terms of covertness.

Paper Structure

This paper contains 25 sections, 5 theorems, 100 equations, 10 figures, 2 algorithms.

Table of Contents

  1. Introduction
  2. System Model
  3. Transmission Strategy and Achievable Rate Analysis
  4. Transmission strategy in the PSR Case
  5. Transmission strategy in the CSR Case
  6. Covert Signal Detection at Warden
  7. The PSR case
  8. The CSR case
  9. Covert Performance Anaysis
  10. Joint Power and IRS Beamforming Design
  11. Problem Formulation and Reformulation
  12. The PSR case
  13. The CSR case
  14. The Optimization of IRS's Phase Shifts
  15. The PSR case
  16. ...and 10 more sections

Key Result

Proposition 1

For the case of $M\to\infty$, the complex Gaussian random variables ${\bf g}_S^H {\bf \Theta g}_B$ and ${\bf g}_B^H {\bf \Theta g}_W$ are i.i.d.

Figures (10)

  • Figure 1: Covert communication in IRS-assisted SR system.
  • Figure 2: Transmission frame for the CSR case within a channel coherence time.
  • Figure 3: The average DEP versus the average transmit power of the source with $\alpha=0.2$.
  • Figure 4: Convergence behavior of the developed algorithm with $P_{\max}=\text{25dBm}$, $\epsilon_{sic}=\text{2bps/Hz}$ and $\epsilon_{c}=\text{0.5bps/Hz}$.
  • Figure 5: Maximal average DEP versus the transmit power of the source.
  • ...and 5 more figures

Theorems & Definitions (6)

  • Remark 1
  • Proposition 1
  • Theorem 1
  • Proposition 2
  • Proposition 3
  • Lemma 1