STAR-RIS Aided Covert Communication

TL;DR

This paper proposes a STAR-RIS-assisted multi-antenna covert communication scheme that maximizes covert rate while ensuring covertness against a warden, using an iterative beamforming optimization algorithm.

Contribution

It introduces a novel STAR-RIS-assisted covert communication framework with a closed-form DEP expression and an iterative GCMMA-based optimization algorithm.

Findings

STAR-RIS significantly improves covert communication performance

The proposed scheme achieves higher covert rates than conventional RIS

The optimization algorithm effectively balances covertness and QoS constraints

Abstract

This paper investigates the multi-antenna covert communications assisted by a simultaneously transmitting and reflecting reconfigurable intelligent surface (STAR-RIS). In particular, to shelter the existence of communications between transmitter and receiver from a warden, a friendly full-duplex receiver with two antennas is leveraged to make contributions to confuse the warden. Considering the worst case, the closed-form expression of the minimum detection error probability (DEP) at the warden is derived and utilized as a covert constraint. Then, we formulate an optimization problem maximizing the covert rate of the system under the covertness constraint and quality of service (QoS) constraint with communication outage analysis. To jointly design the active and passive beamforming of the transmitter and STAR-RIS, an iterative algorithm based on globally convergent version of method of moving asymptotes (GCMMA) is proposed to effectively solve the non-convex optimization problem. Simulation results show that the proposed STAR-RIS-assisted scheme highly outperforms the case with conventional RIS.