Full duplex (FD) systems suffer from very high hardware cost and high power consumption to mitigate the self-interference (SI) in the analog domain. Moreover, in millimeter wave (mmWave) they rely on hybrid beamforming (HYBF) as a signal processing tool to partially deal with the SI, which presents many drawbacks such as high insertion loss and high power consumption. This article proposes the use of near-field (NF-) IRSs for FD systems with the objective to solve the aforementioned issues cost-efficiently. Namely, we propose to truncate the analog/hybrid beamforming stage of the mmWave FD systems and compensate it with an NF-IRS, to simultaneously and smartly control the uplink (UL) and downlink (DL) channels, while assisting in shaping the SI channel: this to obtain very strong passive SI cancellation. A novel joint active and passive beamforming design for the weighted sum-rate (WSR) maximization of a NF-IRS-assisted mmWave point-to-point FD system is presented. Results show that the proposed solution fully reaps the benefits of the IRSs only when they operate in the NF, which leads to considerably higher gains compared to the conventional massive MIMO (mMIMO) mmWave FD and half duplex (HD) systems.

翻译：全双工系统在模拟域中为抑制自干扰而面临极高的硬件成本和功耗。此外，在毫米波频段中，该系统依赖混合波束赋形作为信号处理工具以部分消除自干扰，但混合波束赋形存在插入损耗高、功耗大等缺陷。本文提出将近场智能反射面应用于全双工系统，旨在以经济高效的方式解决上述问题。具体而言，我们拟截断毫米波全双工系统的模拟/混合波束赋形阶段，并通过近场智能反射面进行补偿，从而同时智能控制上行和下行信道，同时辅助塑造自干扰信道，以实现极强的无源自干扰消除。针对近场智能反射面辅助的毫米波点对点全双工系统，本文提出一种新颖的联合有源与无源波束赋形设计，以最大化加权和速率。结果表明，所提方案仅在智能反射面工作于近场时才能充分获益，与传统的毫米波大规模MIMO全双工和半双工系统相比，可实现显著更高的性能增益。