Abstract
Extremely large aperture array (ELAA) is anticipated to serve as a pivotal
feature of future multiple-input multiple-output (MIMO) systems in 6G.
Near-field (NF) fading channel models are essential for reliable link-level
simulation and ELAA system design. In this article, we propose a framework
designed to generate NF fading channels for both communication and integrated
sensing and communication (ISAC) applications. The framework allows a mixed of
line of sight (LoS) and non-LoS (NLoS) links. It also considers spherical wave
model and spatially non-stationary shadow fading. Based on this framework, we
propose a three-dimensional (3D) fading channel model for ELAA systems deployed
with a uniform rectangular array (URA). It can capture the impact of sensing
object for ISAC applications. Moreover, all parameters involved in the
framework are based on specifications or measurements from the 3rd Generation
Partnership Project (3GPP) documents. Therefore, the proposed framework and
channel model have the potential to contribute to the standard in various
aspects, including ISAC, extra-large (XL-) MIMO, and reconfigurable intelligent
surface (RIS) aided MIMO systems. Finally, future directions for ELAA are
presented, including not only NF channel modeling but also the design of
next-generation transceivers.