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arXiv 2406.04262eess.SP
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基于稀疏DFT码本的近场波束训练

Near-field Beam Training with Sparse DFT Codebook

Cong Zhou, Chenyu Wu, Changsheng You, Shuo Shi

AI总结:

针对XL-array近场二维波束搜索开销过高的问题,提出基于稀疏DFT码本的三阶段角度与距离训练方案,在高SNR下减少98.67%开销且不损失速率性能。

摘要:

超大规模阵列(XL-array)已成为提升未来第六代(6G)无线系统频谱效率和空间分辨率的一项有前景技术。天线数量的激增使用户更可能位于近场区域,这需要更精确的球面波前(而非平面波前)传播建模。在角度域和距离域执行二维(2D)波束搜索时,这不可避免地带来难以承受的波束训练开销。为解决该问题,我们首先引入一种新的稀疏离散傅里叶变换(DFT)码本,该码本在用户接收波束方向图中表现出角度周期性,这启发我们提出一种三阶段波束训练方案。具体而言,在第一阶段,我们利用稀疏DFT码本在角度子空间中进行波束扫描,并根据接收波束方向图估计候选用户角度。随后,激活中央子阵列扫描特定候选角度,以解决角度模糊问题并识别用户角度。在第三阶段,在估计角度上应用极域码本,以搜索用户的最佳有效距离。最后,数值结果表明,与穷举搜索方案相比,由稀疏DFT码本赋能的所提波束训练方案实现了98.67%的开销降低,同时在高信噪比(SNR)区域不损失速率性能。

英文摘要:

Extremely large-scale array (XL-array) has emerged as one promising technology to improve the spectral efficiency and spatial resolution of future sixth generation (6G) wireless systems.The upsurge in the antenna number antennas renders communication users more likely to be located in the near-field region, which requires a more accurate spherical (instead of planar) wavefront propagation modeling.This inevitably incurs unaffordable beam training overhead when performing a two-dimensional (2D) beam-search in both the angular and range domains.To address this issue, we first introduce a new sparse discrete Fourier transform (DFT) codebook, which exhibits the angular periodicity in the received beam pattern at the user, which motivates us to propose a three-phase beam training scheme.Specifically, in the first phase, we utilize the sparse DFT codebook for beam sweeping in an angular subspace and estimate candidate user angles according to the received beam pattern.Then, a central sub-array is activated to scan specific candidate angles for resolving the issue of angular ambiguity and identity the user angle.In the third phase, the polar-domain codebook is applied in the estimated angle to search the best effective range of the user.Finally, numerical results show that the proposed beam training scheme enabled by sparse DFT codebook achieves 98.67% reduction as compared with the exhaustive-search scheme, yet without compromising rate performance in the high signal-to-ratio (SNR) regime.

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