Near-Field Beamforming for Extremely Large-Scale Antenna Array

Extremely large-scale arrays is a vital technology for enhancing the capacity in wireless communications. The employment of extremely large-scale arrays makes the near-field propagation become dominant, where the achievable rate is decreased owing to beam mismatch. However, the integration of angle and distance information must be investigated in the near-field beam domain, due to the spherical nature of electromagnetic wave propagation. Thus, in this paper, we propose a beamforming algorithm to mitigate the beam mismatch. We derive the phase profile of extremely large-scale uniform planar array under the spherical wave assumption, and design the visibility region strategy to capture the non-stationarity characteristics of extremely large-scale antenna arrays. Numerical results validate that the proposed algorithm is robust against the beam misfocus effect and performs with a higher achievable transmission rate.