Cross-Far-and-Near-Field Channel Measurement and Modeling in Extremely Large-Scale Movable Antenna Array Systems

Technologies such as ultra-massive multiple-inputmultiple- output and reconfigurable intelligent surfaces are of special interest for achieving the key performance indicators of future wireless systems, including ubiquitous connectivity and lightning-fast data rates. A common feature of these technologies is the extremely large-scale antenna array (ELAA) systems, which consist of hundreds or thousands of antennas. These systems give rise to near-field (NF) propagation, as evidenced by the variations in large-scale and small-scale parameters observed across the ELAA in multiple cross-field experiments conducted at 290 GHz. In light of the new challenges in channel modeling and characterization across the far-field (FF) and the near-field, a general cross-field model framework for ELAA systems is proposed. Specifically in this model, a comprehensive analysis of various cross-field boundaries and closed-form expressions of corresponding NF or FF parameters is provided. Based on this model, extensive simulations are performed for ELAAs of varying sizes in indoor and urban macro-cell scenarios at frequency bands ranging from sub-6 GHz, millimeter-wave up to terahertz (THz). By considering the spherical-wave front as the ground truth, the cross-field model exponentially enhances the accuracy in characterizing multi-path parameters and evaluating the system capacity.