Due to the dramatic increase in high data rate services and in order to meet the demands of the fifth-generation (5G) networks, researchers from both academia and industry are exploring advanced transmission techniques, new network architectures and new frequency spectrum such as the visible light and the millimeter wave (mmWave) spectra. Visible light communication (VLC) particularly is an emerging technology that has been introduced as a promising solution for 5G and beyond, owing to the large unexploited spectrum, which translates to significantly high data rates. Although VLC systems are more immune against interference and less susceptible to security vulnerabilities since light does not penetrate through walls, security issues arise naturally in VLC channels due to their open and broadcasting nature, compared to fiber-optic systems. In addition, since VLC is considered to be an enabling technology for 5G, and security is one of the 5G fundamental requirements, security issues should be carefully addressed and resolved in the VLC context. On the other hand, due to the success of physical layer security (PLS) in improving the security of radio-frequency (RF) wireless networks, extending such PLS techniques to VLC systems has been of great interest. Only two survey papers on security in VLC have been published in the literature. However, a comparative and unified survey on PLS for VLC from information theoretic and signal processing point of views is still missing. This paper covers almost all aspects of PLS for VLC, including different channel models, input distributions, network configurations, precoding/signaling strategies, and secrecy capacity and information rates. Furthermore, we propose a number of timely and open research directions for PLS-VLC systems, including the application of measurement-based indoor and outdoor channel models, incorporating user mobility and device orientation into the channel model, and combining VLC and RF systems to realize the potential of such technologies.

中文翻译：

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可见光通信系统的物理层安全性：调查

由于高速率业务的急剧增加，为了满足第五代（5G）网络的需求，学术界和工业界的研究人员正在探索先进的传输技术、新的网络架构和新的频谱，如可见光。光和毫米波 (mmWave) 光谱。可见光通信 (VLC) 特别是一种新兴技术，由于未开发的大频谱可转化为极高的数据速率，因此已作为 5G 及更高版本的有前途的解决方案引入。尽管 VLC 系统对干扰具有更强的免疫力，并且由于光不能穿透墙壁而不易受到安全漏洞的影响，但与光纤系统相比，由于 VLC 频道的开放和广播性质，安全问题自然会出现。此外，由于 VLC 被认为是 5G 的一项使能技术，而安全性是 5G 的基本要求之一，因此应在 VLC 环境中仔细解决和解决安全问题。另一方面，由于物理层安全 (PLS) 在提高射频 (RF) 无线网络的安全性方面取得了成功，将这种 PLS 技术扩展到 VLC 系统引起了人们的极大兴趣。文献中仅发表了两篇关于 VLC 安全性的调查论文。然而，仍然缺乏从信息论和信号处理的角度对 VLC 的 PLS 进行比较和统一的调查。本文几乎涵盖了 VLC 的 PLS 的所有方面，包括不同的信道模型、输入分布、网络配置、预编码/信令策略以及保密容量和信息速率。