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

2026-01-14

AI Summary

This work addresses the severe degradation of multiuser connectivity in high-frequency radiative near-field communications caused by knife-edge shadowing from indoor half-space obstacles such as walls and corners, which truncates conventional focused beams and collapses the effective channel rank. To overcome this, the authors propose an analog beamforming strategy leveraging the self-bending property of Airy beams, optimizing their curved trajectory so that the main lobe “rides” along obstacle edges into shadowed regions, thereby restoring full-rank links for blocked users. A zero-point steering mechanism is further designed to align oscillatory nulls in mixed illuminated-shadowed scenarios, suppressing interference in bright zones. A Green’s function–based radiative near-field multiuser channel model elucidates the singular value collapse under shadowing. Experimental results demonstrate that the proposed method, requiring no additional hardware, achieves over 20 dB SNR gain in shadowed links and improves multiuser spectral efficiency by approximately 35% with typical indoor extremely large-scale antenna arrays.

Technology Category

• Search and Optimization: Non-convex Optimization
• Machine Learning: Efficient ML / Green AI
• Planning, Routing, and Scheduling: Scheduling under Uncertainty

Application Category

• User Modeling, Personalization and Recommendation: On-Device user modeling, personalization, and recommendation
• Security and Privacy: Large-scale security measurements
• Systems and Infrastructure for Web, Mobile and WoT: Energy management for devices in mobile Web and WoT environments

Abstract

The move to next-generation wireless communications with extremely large-scale antenna arrays (ELAAs) brings the communications into the radiative near-field (RNF) region, where distance-aware focusing is feasible. However, high-frequency RNF links are highly vulnerable to blockage in indoor environments dominated by half-space obstacles (walls, corners) that create knife-edge shadows. Conventional near-field focused beams offer high gain in line-of-sight (LoS) scenarios but suffer from severe energy truncation and effective-rank collapse in shadowed regions, often necessitating the deployment of auxiliary hardware such as Reconfigurable Intelligent Surfaces (RIS) to restore connectivity. We propose a beamforming strategy that exploits the auto-bending property of Airy beams to mitigate half-space blockage without additional hardware. The Airy beam is designed to ``ride''the diffraction edge, accelerating its main lobe into the shadow to restore connectivity. Our contributions are threefold: (i) a Green's function-based RNF multi-user channel model that analytically reveals singular-value collapse behind knife-edge obstacles; (ii) an Airy analog beamforming scheme that optimizes the bending trajectory to recover the effective channel rank; and (iii) an Airy null-steering method that aligns oscillatory nulls with bright-region users to suppress interference in mixed shadow/bright scenarios. Simulations show that the proposed edge-riding Airy strategy achieves a Signal-to-Noise Ratio (SNR) improvement of over 20 dB and restores full-rank connectivity in shadowed links compared to conventional RNF focusing, virtually eliminating outage in geometric shadows and increasing multi-user spectral efficiency by approximately 35\% under typical indoor ELAA configurations. These results demonstrate robust RNF multi-user access in half-space blockage scenarios without relying on RIS.

Problem

• radiative near-field
• half-space blockage
• knife-edge shadow
• multi-user access
• extremely large-scale antenna arrays

Innovation

• Airy beams
• radiative near-field
• half-space blockage
• beamforming
• knife-edge diffraction