A near-field secure transmission framework is proposed. Employing the hybrid beamforming architecture, a multi-antenna base station (BS) transmits confidential information to a multi-antenna legitimate user (U) against a multi-antenna eavesdropper (E) in the near field. A two-stage algorithm is proposed to maximize the near-field secrecy capacity. Based on the fully-digital beamformers obtained in the first stage, the optimal analog beamformers and baseband digital beamformers can be alternatingly derived in the closed-form expressions in the second stage. Numerical results demonstrate that in contrast to the far-field secure communication relying on the angular disparity, the near-field secure communication mainly relies on the distance disparity between U and E.
@article{arxiv.2302.04189,
title = {Physical Layer Security in Near-Field Communications},
author = {Zheng Zhang and Yuanwei Liu and Zhaolin Wang and Xidong Mu and Jian Chen},
journal= {arXiv preprint arXiv:2302.04189},
year = {2023}
}