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

TL;DR

This paper explores covert communication in IRS-assisted symbiotic radio systems, proposing optimized strategies for power and reflection control to enhance covertness against detection, with validated numerical results.

Contribution

It introduces a novel double reflection link design and joint optimization algorithms for covert communication in IRS-assisted symbiotic radio systems.

Findings

Proposed optimal power and reflection strategies improve covertness.

Derived analytical expression for detection error probability.

Numerical results confirm strategy effectiveness and accuracy.

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.