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

Technologies such as ultramassive multiple-input-multiple-output (UM-MIMO) and reconfigurable intelligent surfaces (RISs) 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 NF, 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 macrocell scenarios at frequency bands ranging from sub-6 GHz, millimeter-wave up to terahertz (THz). By considering the spherical wavefront as the ground truth, the cross-field model exponentially enhances the accuracy in characterizing multipath parameters and evaluating the system capacity.