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Wireless Communication for Low-Altitude Economy with UAV Swarm Enabled Two-Level Movable Antenna System

Haiquan Lu, Yong Zeng, Shaodan Ma, Bin Li, Shi Jin, Rui Zhang

TL;DR

This paper proposes a UAV swarm enabled two-level movable-antenna system to enhance uplink communication for low-altitude economy applications. It jointly optimizes 3D UAV placement, MA positions, and receive beamforming to maximize the minimum ground-user rate, leveraging both swarm mobility and intra-UAV MA adjustments. For single-antenna UAVs, key insights include SNR scaling with the number of UAVs and closed-form IUI-free placements forming a Uniform Sparse Array in the two-UE case, with an efficient alternating optimization for multiple UEs. The multi-antenna extension preserves these gains, demonstrating substantial rate improvements over benchmark schemes and providing an error-compensation scheme to counter synchronization and position uncertainties. Overall, the two-level mobility framework offers a practical path to high-capacity, reliable wireless connectivity in dynamic, low-altitude environments.

Abstract

Unmanned aerial vehicle (UAV) is regarded as a key enabling platform for low-altitude economy, due to its advantages such as 3D maneuverability, flexible deployment, and LoS air-to-air/ground communication links. In particular, the intrinsic high mobility renders UAV especially suitable for operating as a movable antenna (MA) from the sky. In this paper, by exploiting the flexible mobility of UAV swarm and antenna position adjustment of MA, we propose a novel UAV swarm enabled two-level MA system, where UAVs not only individually deploy a local MA array, but also form a larger-scale MA system with their individual MA arrays via swarm coordination. We formulate a general optimization problem to maximize the minimum achievable rate over all ground user equipments (UEs), by jointly optimizing the 3D UAV swarm placement positions, their individual MAs' positions, and receive beamforming for different UEs. To gain useful insights, we first consider the special case where each UAV has only one antenna, under different scenarios of one single UE, two UEs, and arbitrary number of UEs. In particular, for the two-UE case, we derive the optimal UAV swarm placement positions in closed-form that achieves IUI-free communication when the uniform plane wave (UPW) model holds, where the UAV swarm forms a uniform sparse array (USA) satisfying minimum safe distance constraint. While for the general case with arbitrary number of UEs, we propose an efficient alternating optimization algorithm to solve the formulated non-convex optimization problem. Then, we extend the results to the case where each UAV is equipped with multiple antennas. Numerical results verify that the proposed low-altitude UAV swarm enabled MA system significantly outperforms various benchmark schemes, thanks to the exploitation of two-level mobility to create more favorable channel conditions for multi-UE communications.

Wireless Communication for Low-Altitude Economy with UAV Swarm Enabled Two-Level Movable Antenna System

TL;DR

This paper proposes a UAV swarm enabled two-level movable-antenna system to enhance uplink communication for low-altitude economy applications. It jointly optimizes 3D UAV placement, MA positions, and receive beamforming to maximize the minimum ground-user rate, leveraging both swarm mobility and intra-UAV MA adjustments. For single-antenna UAVs, key insights include SNR scaling with the number of UAVs and closed-form IUI-free placements forming a Uniform Sparse Array in the two-UE case, with an efficient alternating optimization for multiple UEs. The multi-antenna extension preserves these gains, demonstrating substantial rate improvements over benchmark schemes and providing an error-compensation scheme to counter synchronization and position uncertainties. Overall, the two-level mobility framework offers a practical path to high-capacity, reliable wireless connectivity in dynamic, low-altitude environments.

Abstract

Unmanned aerial vehicle (UAV) is regarded as a key enabling platform for low-altitude economy, due to its advantages such as 3D maneuverability, flexible deployment, and LoS air-to-air/ground communication links. In particular, the intrinsic high mobility renders UAV especially suitable for operating as a movable antenna (MA) from the sky. In this paper, by exploiting the flexible mobility of UAV swarm and antenna position adjustment of MA, we propose a novel UAV swarm enabled two-level MA system, where UAVs not only individually deploy a local MA array, but also form a larger-scale MA system with their individual MA arrays via swarm coordination. We formulate a general optimization problem to maximize the minimum achievable rate over all ground user equipments (UEs), by jointly optimizing the 3D UAV swarm placement positions, their individual MAs' positions, and receive beamforming for different UEs. To gain useful insights, we first consider the special case where each UAV has only one antenna, under different scenarios of one single UE, two UEs, and arbitrary number of UEs. In particular, for the two-UE case, we derive the optimal UAV swarm placement positions in closed-form that achieves IUI-free communication when the uniform plane wave (UPW) model holds, where the UAV swarm forms a uniform sparse array (USA) satisfying minimum safe distance constraint. While for the general case with arbitrary number of UEs, we propose an efficient alternating optimization algorithm to solve the formulated non-convex optimization problem. Then, we extend the results to the case where each UAV is equipped with multiple antennas. Numerical results verify that the proposed low-altitude UAV swarm enabled MA system significantly outperforms various benchmark schemes, thanks to the exploitation of two-level mobility to create more favorable channel conditions for multi-UE communications.

Paper Structure

This paper contains 20 sections, 3 theorems, 72 equations, 10 figures, 2 algorithms.

Table of Contents

  1. Introduction
  2. System Model And Problem Formulation
  3. Special Case of Single-Antenna UAV
  4. Single UE and Two UEs
  5. Arbitrary Number of UEs
  6. Optimization of ${\bf V}$ With Given ${\bf Q}$
  7. Optimization of ${{\bf{q}}_l}$ With Given ${\bf V}$ and $\left\{ {{\bf{q}}_{l'} ,\forall l' \ne l} \right\}$
  8. Multi-Antenna UAV
  9. Single UE and Two UEs
  10. Arbitrary Number of UEs
  11. Optimization of ${\bf V}$ With Given ${\bf Q}$ and ${\bf B}$
  12. Optimization of ${{\bf{q}}_l}$ With Given ${\bf V}$, $\left\{ {{\bf{q}}_{l'},\forall l' \ne l} \right\}$, and $\bf B$
  13. Optimization of ${b_{l,m}}$ With Given ${\bf V}$, ${\bf Q}$, and $\left\{ {{b_{l',m'}},\forall l' \ne l,m' \ne m} \right\}$
  14. Numerical Results
  15. Single-Antenna UAV
  16. ...and 5 more sections

Key Result

Theorem 1

An optimal solution to OptimizationProblemTwoUE that achieves zero objective value is where ${{\bf{q}}_1}$ can be any vector to guarantee ${{\bf{q}}_l} \in {\cal C}$, $\forall l$, and ${\varsigma^{\star}}$ is given by

Figures (10)

  • Figure 1: Wireless communication with a low-altitude UAV swarm enabled two-level MA system.
  • Figure 2: The channels' squared-correlation coefficient ${\xi _{1,2}}$ versus $\varsigma$ and $\Gamma$.
  • Figure 3: Convergence behaviour of Algorithm \ref{['alg1']}.
  • Figure 4: The minimum achievable rate versus the transmit power of each UE for the two-UE communication in the single-antenna UAV case.
  • Figure 5: The SNR loss factor versus the transmit power for the two-UE communication in the single-antenna UAV case.
  • ...and 5 more figures

Theorems & Definitions (3)

  • Theorem 1
  • Lemma 1
  • Proposition 1