Directional modulation (DM), as an efficient secure transmission method, offers security through its directive property and is suitability for LoP channels such as millimeter wave, UAV, satellite communication, and smart transportation. If the direction angle of the desired user is known, the desired channel gain vector is obtainable. Thus, in advance, the DM transmitter knows the values of the directional angles of the desired user and eavesdropper, or their DOAs because the BVCM andANPM are mainly determined by the directional angles of the desired user and eavesdropper. For a DM transceiver, working as a receiver, the first step is to measure the DOAs of the desired user and eavesdropper. Then, in the second step, using the measured DOAs, the BVCM and ANPM are designed. In this article, we describe DOA measurement methods, power allocation, and beamforming in DM networks. A machine learning-based DOA measurement method is proposed to make a substantial secrecy rate (SR) performance gain compared to single-snapshot measurement without machine learning for a given null-space projection beamforming scheme. However, for a conventional DM network, there still exists a serious security issue: the eavesdropper moves inside the main beam of the desired user and may intercept the CMs intended for the desired users because the BVCM and ANPM are only angle-dependent. To address this problem, we present a new concept of SPWT, where the transmit waveform has two-dimensional dependency by using DM, random subcarrier selection with randomization procedure, and phase alignment at the DM transmitter.

中文翻译：

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定向调制：B5G 和未来无线网络的物理层安全解决方案


定向调制（DM）作为一种高效的安全传输方法，通过其方向性提供安全性，适用于毫米波、无人机、卫星通信、智能交通等LoP信道。如果已知期望用户的方向角，则可以获得期望的信道增益矢量。因此，DM发射机预先知道期望用户和窃听者的方向角的值，或者他们的DOA，因为BVCM和ANPM主要由期望用户和窃听者的方向角确定。对于作为接收器工作的 DM 收发器，第一步是测量所需用户和窃听者的 DOA。然后，在第二步中，使用测量的 DOA，设计 BVCM 和 ANPM。在本文中，我们描述 DM 网络中的 DOA 测量方法、功率分配和波束成形。针对给定的零空间投影波束形成方案，提出了一种基于机器学习的 DOA 测量方法，与没有机器学习的单快照测量相比，可显着提高保密率 (SR) 性能。然而，对于传统的DM网络来说，仍然存在严重的安全问题：窃听者在目标用户的主波束内移动，并且可能拦截针对目标用户的CM，因为BVCM和ANPM仅与角度相关。为了解决这个问题，我们提出了 SPWT 的新概念，其中通过使用 DM、具有随机化过程的随机子载波选择以及 DM 发射机的相位对齐，使发射波形具有二维相关性。