# Near-Field Wideband Beam Training Based on Distance-Dependent Beam Split

arXiv: https://arxiv.org/abs/2406.07989 · HTML: https://mlsanity.com/paper/2406.07989/

## Key facts

- Cited by 2 papers in the map (data through 14 Oct 2026).
- First posted on arXiv 12 Jun 2024.

## Built on by (most cited first, 2 of 2)

- [SPOT: Single-Shot Positioning via Trainable Near-Field Rainbow Beamforming](https://mlsanity.com/paper/2511.11391/) (2025)
- [Near-Field Wideband Channel Estimation for XL-MIMO Systems via Denoising Diffusion Model](https://mlsanity.com/paper/2604.20494/) (2026)

## Abstract (arXiv)

Near-field beam training is essential for acquiring channel state information in 6G extremely large-scale multiple input multiple output (XL-MIMO) systems. To achieve low-overhead beam training, existing method has been proposed to leverage the near-field beam split effect, which deploys true-time-delay arrays to simultaneously search multiple angles of the entire angular range in a distance ring with a single pilot. However, the method still requires exhaustive search in the distance domain, which limits its efficiency. To address the problem, we propose a distance-dependent beam-split-based beam training method to further reduce the training overheads. Specifically, we first reveal the new phenomenon of distance-dependent beam split, where by manipulating the configurations of time-delay and phase-shift, beams at different frequencies can simultaneously scan the angular domain in multiple distance rings. Leveraging the phenomenon, we propose a near-field beam training method where both different angles and distances can simultaneously be searched in one time slot. Thus, a few pilots are capable of covering the whole angle-distance space for wideband XL-MIMO. Theoretical analysis and numerical simulations are also displayed to verify the superiority of the proposed method on beamforming gain and training overhead.