Movable Frequency Diverse Array-Assisted Covert Communication With Multiple Wardens

TL;DR

This paper introduces a movable FDA (MFDA) system that dynamically adjusts antenna positions to enhance covert communication, especially under multiple wardens and correlated channels, outperforming traditional FDA methods.

Contribution

The paper proposes a novel movable FDA (MFDA) technology with dynamic antenna positioning and develops an optimization algorithm to maximize covert rate under practical CSI constraints.

Findings

MFDA significantly improves covert performance over conventional FDA.

Adjusting antenna positions can increase covert rate when frequency constraints are strict.

Simulation results validate the effectiveness of the proposed MFDA approach.

Abstract

The frequency diverse array (FDA) is highly promising for improving covert communication performance by adjusting the frequency of each antenna at the transmitter. However, when faced with the cases of multiple wardens and highly correlated channels, FDA is limited by the frequency constraint and cannot provide satisfactory covert performance. In this paper, we propose a novel movable FDA (MFDA) antenna technology where positions of the antennas can be dynamically adjusted in a given finite region. Specifically, we aim to maximize the covert rate by jointly optimizing the antenna beamforming vector, antenna frequency vector and antenna position vector. To solve this non-convex optimization problem with coupled variables, we develop a two-stage alternating optimization (AO) algorithm based on the block successive upper-bound minimization (BSUM) method. Moreover, considering the challenge of obtaining perfect channel state information (CSI) at multiple wardens, we study the case of imperfect CSI. Simulation results demonstrate that MFDA can significantly enhance covert performance compared to the conventional FDA. In particular, when the frequency constraint is strict, MFDA can further increase the covert rate by adjusting the positions of antennas instead of the frequencies.