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Six-Dimensional Movable Antenna Enabled Wideband THz Communications

Wencai Yan, Wanming Hao, Yajun Fan, Yabo Guo, Qingqing Wu, Xingwang Li

TL;DR

The paper addresses beam squint in wideband THz communications by introducing six-dimensional movable antennas (6DMA) whose 3D positions and rotations are jointly optimized with a sub-connected hybrid beamforming base station. An alternating-optimization framework combines semidefinite-relaxation-based hybrid beamforming design with feasible gradient-descent updates for 6DMA geometry, achieving superior array gain and sum-rate compared to fixed-position architectures. Key contributions include a normalized array-gain analysis showing geometry-driven squint mitigation, a detailed AO solution for joint optimization, and numerical validation across multiuser scenarios demonstrating robust performance gains and convergence. The work suggests a practical path toward high-capacity THz links with reduced hardware complexity and enhanced adaptability in realistic deployment environments, with future work on hybrid-field 6DMA channel modeling.

Abstract

In this paper, we investigate a six-dimensional movable antenna (6DMA)-enabled wideband terahertz (THz) communication system with sub-connected hybrid beamforming architecture at the base station (BS). In particular, the three-dimensional (3D) position and 3D rotation of each 6DMA surface can be flexibly reconfigured to mitigate the beam squint effects instead of introducing costly true-time-delay devices. We first analyze the normalized array gain in the 6DMA-enabled wideband THz systems based on the beam squint effects. Then, we formulate a sum-rate maximization problem via jointly optimizing 3D positions, 3D rotations, and hybrid analog/digital beamforming. To solve the non-convex problem, an alternating optimization algorithm is developed that decomposes the original problem into three subproblems, which are solved alternately. Specifically, given the positions and rotations of 6DMA surfaces, we first reformulate the objective function and design a semidefinite relaxation-based alternating minimization scheme to obtain the hybrid analog/digital beamforming. Then, the positions and rotations of the 6DMA surfaces are further optimized through a feasible gradient descent procedure. The final solutions are obtained by repeating the above procedure until convergence. Numerical results demonstrate the superior performance of the proposed scheme compared with conventional fixed-position antenna architectures.

Six-Dimensional Movable Antenna Enabled Wideband THz Communications

TL;DR

The paper addresses beam squint in wideband THz communications by introducing six-dimensional movable antennas (6DMA) whose 3D positions and rotations are jointly optimized with a sub-connected hybrid beamforming base station. An alternating-optimization framework combines semidefinite-relaxation-based hybrid beamforming design with feasible gradient-descent updates for 6DMA geometry, achieving superior array gain and sum-rate compared to fixed-position architectures. Key contributions include a normalized array-gain analysis showing geometry-driven squint mitigation, a detailed AO solution for joint optimization, and numerical validation across multiuser scenarios demonstrating robust performance gains and convergence. The work suggests a practical path toward high-capacity THz links with reduced hardware complexity and enhanced adaptability in realistic deployment environments, with future work on hybrid-field 6DMA channel modeling.

Abstract

In this paper, we investigate a six-dimensional movable antenna (6DMA)-enabled wideband terahertz (THz) communication system with sub-connected hybrid beamforming architecture at the base station (BS). In particular, the three-dimensional (3D) position and 3D rotation of each 6DMA surface can be flexibly reconfigured to mitigate the beam squint effects instead of introducing costly true-time-delay devices. We first analyze the normalized array gain in the 6DMA-enabled wideband THz systems based on the beam squint effects. Then, we formulate a sum-rate maximization problem via jointly optimizing 3D positions, 3D rotations, and hybrid analog/digital beamforming. To solve the non-convex problem, an alternating optimization algorithm is developed that decomposes the original problem into three subproblems, which are solved alternately. Specifically, given the positions and rotations of 6DMA surfaces, we first reformulate the objective function and design a semidefinite relaxation-based alternating minimization scheme to obtain the hybrid analog/digital beamforming. Then, the positions and rotations of the 6DMA surfaces are further optimized through a feasible gradient descent procedure. The final solutions are obtained by repeating the above procedure until convergence. Numerical results demonstrate the superior performance of the proposed scheme compared with conventional fixed-position antenna architectures.

Paper Structure

This paper contains 14 sections, 41 equations, 10 figures, 1 table, 4 algorithms.

Table of Contents

  1. Introduction
  2. Related Works
  3. Main Contributions
  4. System Model and Beam Squint Mitigation
  5. System Model
  6. Beam Squint Effects of 6DMA
  7. Problem Formulation and Solution
  8. Problem Formulation
  9. Problem Solution
  10. Hybrid Beamforming Design
  11. Positions and Rotations Optimization
  12. Computational Complexity
  13. Numerical Results
  14. Conclusions

Figures (10)

  • Figure 1: 6DMA-enabled communication system with hybrid beamforming.
  • Figure 2: Illustration of the positions generated on a spherical surface.
  • Figure 3: Beam pattern. (a) Normal vector deviates from the user. (b) Normal vector points towards the user.
  • Figure 4: The normalized array gain across different positions on the spherical surface.
  • Figure 5: Simulation setup.
  • ...and 5 more figures