The Analysis of Beamforming Resolution for Near-Field MIMO Communication Networks

With the rapid development of sixth-generation (6G) wireless networks and large-scale multiple-input multiple-output (MIMO) technology, the traditional far-field plane wave model becomes inaccurate, and a spherical wave model must be employed. We analyze the near-field beamforming resolution and a closed-form approximation of the resolution is derived using the Fresnel approximation and Taylor expansion, revealing its dependence on the number of antennas and user positions. We further provide sufficient conditions to guarantee a desired resolution threshold, and demonstrate that the resulting constraints are monotonic and solvable by efficient numerical methods. Simulation results confirm the accuracy of the proposed approximation and its usefulness in guiding near-field transmission design.