Overcoming Half-Space Blockage: Airy Beamforming for Radiative Near-Field Multiuser XL-MIMO Communications

Abstract

Next-generation wireless systems with extremely large-scale antenna arrays (ELAAs) operate in the radiative near-field (RNF) region, where distance-aware focusing is feasible but is easily interrupted by half-space obstacles such as walls and corners. When the aperture-to-user path is clipped by a knife edge, conventional focused beams are truncated and the multi-user channel suffers a collapse of its weak singular mode that defeats zero-forcing (ZF) precoding. In this paper, a hybrid transmission strategy is proposed in which a low-dimensional Airy radio-frequency beam family, parameterized by only three physical quantities (launch angle, virtual focal length, and signed curvature), is used to carry energy around an accessible diffracting edge, while a digital ZF stage performs the final inter-user cancellation under one explicitly declared total-radiated-power constraint. Channel separability is evaluated on the whitened effective channel, so that non-orthogonal analog beams cannot distort the comparison. In the principal blocked two-user scene, the proposed design attains 4.94 bit/s/Hz, compared with 1.97 for conventional focusing, 4.61 for a caustic construction, 5.93 for unrestricted digital ZF, and 6.47 for an iterative fully digital WMMSE reference, and the whitened smallest singular value is more than doubled. Across 36 blocked-user geometries, the whitened conditioning and the minimum user rate are improved in every case. The approach requires an accessible diffracting edge and does not restore service through a fully opaque plane.