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arXiv · 2608.19416

Robust Near-Field Beam Focusing Under Imperfect Localization

Nima Mozaffarikhosravi·Amirhossein Azarbahram·Prathapasinghe Dharmawansa·Italo Atzeni
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Abstract

The transition to 6G-and-beyond wireless systems with large-scale antenna arrays and high-frequency deployments significantly extends the near-field region, where channels exhibit a strong dependence on user location. While this enables location-based beam focusing as a low-overhead alternative to conventional channel estimation, its performance is highly sensitive to localization errors. In this paper, we study robust near-field beam focusing under imperfect user localization. We explicitly characterize the impact of localization errors on the line-of-sight-dominated channel by deriving a tractable uncertainty model via a first-order Taylor approximation, which captures the coupled effects of distance and angle in near-field propagation. Building on this model, we formulate a max-min signal-to-interference-plus-noise ratio optimization problem that guarantees performance under worst-case channel realizations induced by bounded localization errors. The resulting problem is reformulated into a feasibility problem using semidefinite relaxation. Numerical results demonstrate that the proposed robust design significantly improves the worst-user rate compared to non-robust beam focusing, particularly under high total transmit power levels and large localization error ranges.

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BibTeXRIS

Nima Mozaffarikhosravi, Amirhossein Azarbahram, Prathapasinghe Dharmawansa, Italo Atzeni. 2026-08-19. Robust Near-Field Beam Focusing Under Imperfect Localization. https://arxiv.org/abs/2608.19416

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