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As the commercialization of 5G wireless networks gains momentum, there is a growing emphasis on exploratory research into the upcoming 6G wireless networks. This era of technological advancement sees 6G networks characterized by a more visionary and performance-driven ethos compared to their predecessors. Traditional wireless networks, spanning from 1G to 5G, predominantly operate within a spectrum below 6 GHz, often below 3 GHz. Due to the physical constraints on antenna arrays and the proportional relationship between element spacing and wavelength, these spectrum bands necessitate the use of relatively small numbers of antennas. Consequently, the combined effect of these lower-dimensional antenna arrays and lower frequency bands confines the range of wireless near-field communication to mere meters or even centimeters, thereby shaping the design of these systems around far-field assumptions.

However, the transition to 6G networks is marked by the adoption of larger antenna apertures and higher frequency bands, such as new mid frequency, millimeter wave, and terahertz bands, which accentuate near-field characteristics, as shown in Table 1.1. The integration of emerging technologies such as Reconfigurable Intelligent Surface (RIS)[1][2][3], extremely large aperture arrays (ELAA)[4], movable antenna (MA)[5] and cell-free networks [6] is expected to amplify the prevalence of the near-field scenario in future wireless networks. This shift challenges traditional far-field plane wave assumptions and underscores the need to rethink strategies for spatial resource utilization [7]. While conventional systems have …