[논문 리뷰] Airy Beamforming for Radiative Near-Field MU-XL-MIMO: Overcoming Half-Space Blockage

Yifeng Qin, Jing Chen외 4명|arXiv (Cornell University)|2026. 01. 14.

Advanced Wireless Communication Technologies인용 수 0

한 줄 요약

본 연구는 Airy beamforming을 도입하여 radiative near-field MU-XL-MIMO의 half-space blockage를 극복하고 RIS 없이 채널 랭크와 연결성을 회복하며, SNR 및 스펙트럴 효율의 상당한 이득을 제공합니다.

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.

연구 동기 및 목표

• 실내 환경에서 half-space 장애물(벽, 모서리)을 가진 RNF MU-MIMO를 동기 부여한다.
• Green’s function과 Fresnel 회절을 사용하여 RNF 채널에서 차단 효과와 특이값 붕괴를 모델링한다.
• 블록age 완화를 위한 Airy-beam 기반 아날로그 빔포밍을 개발하여 채널 랭크를 회복한다.
• 혼합 그림자/밝은 영역 시나리오에서 간섭 억제를 위한 Airy-null steering 방법을 제안한다.
• RIS에 의존하지 않고 SNR 및 스펙트럼 효율의 성능 향상을 정량화한다.

제안 방법

• Knife-edge 장애물 뒤에서 특이값 붕괴를 드러내는 Green’s function 기반 RNF MU-MIMO 채널 모델.
• 매개변수 (B, F, theta)로 아날로그 프리코더에 세제곱 위상 변조를 가해 Airy 아날로그 빔포밍.
• 장벽의 경계에 닿도록 Airy 빔 굴절을 최적화하고 그림자 영역을 비추도록 하는 Edge-riding 전략.
• 섞인 시나리오에서 간섭 억제를 위해 진동하는 Airy null을 밝은 영역 사용자와 맞추는 Airy-null steering.
• 차폐된 상태에서 동등 SINR을 분석하기 위해 효과 채널에 제로-포스 프리코딩으로 사용자 스트림을 분리한다.
• 장벽을 통한 회절을 시뮬레이션하고 그림자 내 전파를 포착하기 위한 Fresnel diffraction 기반 차단 모델링.

실험 결과

연구 질문

• RQ1 Can Airy beams mitigate rank collapse and outage caused by half-space blockage in RNF MU-MIMO?
• RQ2 How does edge-riding Airy beamforming compare to conventional focusing in restoring connectivity in geometrically shadowed regions?
• RQ3 Can Airy-beam tails be controlled to suppress interference in mixed shadow/bright scenarios via null steering?
• RQ4 What are the performance gains (SNR, spectral efficiency) when using Airy beamforming without RIS in indoor ELAA configurations?

주요 결과

• Edge-riding Airy beams restore non-zero channel rank behind half-space blockages, dramatically reducing outage relative to conventional focusing.
• Airy beamforming yields over 20 dB SNR improvement in shadowed links compared to traditional RNF focusing.
• Airy-based strategies recover full-rank connectivity and increase multi-user spectral efficiency by about 35% in typical indoor ELAA setups.
• Airy-null steering in mixed shadow/bright scenarios enables interference suppression without sacrificing shadowed-user performance.
• A simple fixed-geometry Airy codebook with parameters (B, F, theta) can substantially outperform baseline blockage scenarios without per-user optimization.
• The approach demonstrates robust RNF MU-MIMO operation in half-space blockage without RIS.