In this work, we study a six-dimensional movable antenna (6DMA)-enhanced Terahertz (THz) network that supports a large number of users with a few antennas by controlling the three-dimensional (3D) positions and 3D rotations of antenna surfaces/subarrays at the base station (BS). However, the short wavelength of THz signals combined with a large 6DMA movement range extends the near-field region. As a result, a user can be in the far-field region relative to the antennas on one 6DMA surface, while simultaneously residing in the near-field region relative to other 6DMA surfaces. Moreover, 6DMA THz channel estimation suffers from increased computational complexity and pilot overhead due to uneven power distribution across the large number of candidate position-rotation pairs, as well as the limited number of radio frequency (RF) chains in THz bands. To address these issues, we propose an efficient hybrid-field generalized 6DMA THz channel model, which accounts for planar wave propagation within individual 6DMA surfaces and spherical waves among different 6DMA surfaces. Furthermore, we propose a low-overhead channel estimation algorithm that leverages directional sparsity to construct a complete channel map for all potential antenna position-rotation pairs. Numerical results show that the proposed hybrid-field channel model achieves a sum rate close to that of the ground-truth near-field channel model and confirm that the channel estimation method yields accurate results with low complexity.

翻译：本文研究了一种六维可动天线增强的太赫兹网络，通过控制基站天线面/子阵的三维位置与三维旋转，利用少量天线支持大量用户。然而，太赫兹信号的短波长与六维可动天线的大范围移动扩展了近场区域，导致一个用户可能相对于某个六维可动天线面上的天线处于远场区域，同时相对于其他六维可动天线面处于近场区域。此外，六维可动天线太赫兹信道估计面临计算复杂度与导频开销增加的问题，其原因在于大量候选位置-旋转对之间的功率分布不均衡，以及太赫兹频段射频链数量有限。针对上述问题，本文提出一种高效混合场广义六维可动天线太赫兹信道模型，该模型同时考虑单个六维可动天线面内的平面波传播与不同六维可动天线面间的球面波传播。进一步，我们提出一种低开销信道估计算法，利用方向稀疏性构建所有潜在天线位置-旋转对的完整信道映射。数值结果表明，所提混合场信道模型的和速率接近真实近场信道模型，且信道估计方法能以低复杂度获得精确结果。