Multiple-antenna technologies are advancing towards large-scale aperture sizes and extremely high frequencies, leading to the emergence of near-field communications (NFC) in future wireless systems. To this context, we investigate the degree of freedom (DoF) in near-field multiple-input multiple-output (MIMO) systems. We consider both spatially discrete (SPD) antennas and continuous aperture (CAP) antennas. Additionally, we explore three important DoF-related performance metrics and examine their relationships with the classic DoF. Numerical results demonstrate the benefits of NFC over far-field communications (FFC) in terms of providing increased spatial DoFs. We also identify promising research directions for NFC from a DoF perspective.
@article{arxiv.2308.00362,
title = {Near-Field Communications: A Degree-of-Freedom Perspective},
author = {Chongjun Ouyang and Yuanwei Liu and Xingqi Zhang and Lajos Hanzo},
journal= {arXiv preprint arXiv:2308.00362},
year = {2023}
}