Towed Movable Antenna (ToMA) Array for Ultra Secure Airborne Communications

TL;DR

This paper introduces a towed movable antenna array for airborne communications, enhancing security and beamforming flexibility by enabling dynamic 3D deployment around aircraft, outperforming fixed onboard arrays.

Contribution

It presents a novel ToMA array architecture with optimized antenna positioning for improved physical layer security in airborne systems.

Findings

Significant performance gains over fixed arrays in secure communication scenarios.

Optimal antenna positioning reduces channel correlation between users and eavesdroppers.

The proposed algorithm effectively maximizes ergodic achievable rates in multiuser settings.

Abstract

This paper proposes a novel towed movable antenna (ToMA) array architecture to enhance the physical layer security of airborne communication systems. Unlike conventional onboard arrays with fixed-position antennas (FPAs), the ToMA array employs multiple subarrays mounted on flexible cables and towed by distributed drones, enabling agile deployment in three-dimensional (3D) space surrounding the central aircraft. This design significantly enlarges the effective array aperture and allows dynamic geometry reconfiguration, offering superior spatial resolution and beamforming flexibility. We consider a secure transmission scenario where an airborne transmitter communicates with multiple legitimate users in the presence of potential eavesdroppers. To ensure security, zero-forcing beamforming is employed to nullify signal leakage toward eavesdroppers. Based on the statistical distributions of locations of users and eavesdroppers, the antenna position vector (APV) of the ToMA array is optimized to maximize the users' ergodic achievable rate. Analytical results for the case of a single user and a single eavesdropper reveal the optimal APV structure that minimizes their channel correlation. For the general multiuser scenario, we develop a low-complexity alternating optimization algorithm by leveraging Riemannian manifold optimization. Simulation results confirm that the proposed ToMA array achieves significant performance gains over conventional onboard FPA arrays, especially in scenarios where eavesdroppers are closely located to users under line-of-sight (LoS)-dominant channels.