Breaking Near-Field Communication Barriers: Focused, Curved, or Airy Beamforming?
Shupei Zhang, Boya Di, Lingyang Song
Abstract
To meet the requirements for high data rates and ubiquitous connectivity in 6G networks, higher frequencies and larger array apertures are employed to enhance spatial resolution and spectral efficiency. This evolution leads to an expansion of the near-field region, where spherical-wave focusing can significantly enhance received power. However, the pervasive presence of obstacles in near-field environments makes communication in obstructed scenarios a critical challenge, particularly for sensitive high-frequency links with high penetration losses. In this paper, we propose a new waveform, termed the near-field Airy beam, which is tailored to the amplitude and phase characteristics of obstructed near-field channels. By integrating non-uniform amplitude response with non-linear phase profile, the proposed Airy beam forms specific curved trajectories, energy distributions, and focal points, enabling energy concentration at the user even after circumventing obstacles. An Airy beamforming algorithm is also developed for hybrid beamformer architectures. Considering practical conditions with unknown obstacle and user locations, we design an Airy beam codebook and a low-overhead hierarchical search scheme to identify the optimal user-aligned beam. Simulation results demonstrate that in obstructed environments, the near-field Airy beam achieves a received power gain of over 3 dB compared to conventional waveforms like focused and curved beams, closely approaching the theoretical upper bound. Across the mmWave to THz bands and various obstacle dimensions, the proposed beam training scheme consistently outperforms traditional methods in terms of spectral efficiency while maintaining a comparable training overhead.