Interference Characterization and Mitigation in Near-Field XL-MIMO: A Case for Linear and Circular Array Geometries

Extremely large-scale multiple-input multipleoutput (XL-MIMO) introduces near-field communication regime due to its large antenna aperture in which spherical wavefronts and beam focusing replace conventional far-field assumptions. This shift significantly impacts interference behavior, especially for near-field users who are affected by both near-and far-field interferers. In this letter, we derive a closed-form expression for total interference and analyze the spectral efficiency for different array geometries. Our results reveal that uniform circular arrays (UCAs) outperform uniform linear arrays (ULAs) in the near-field by generating Bessel-like beams that enhance spatial focusing and significantly reduce interference.