Optical Communications Laboratory, Ocean College, Zhejiang University, Zheda Road 1, Zhoushan 316021, China.
Shenzhen Institute of Information Technology, Shenzhen 518172, China.
Sensors (Basel). 2023 Mar 9;23(6):2960. doi: 10.3390/s23062960.
The enhanced proliferation of connected entities needs a deployment of innovative technologies for the next generation wireless networks. One of the critical concerns, however, is the spectrum scarcity, due to the unprecedented broadcast penetration rate nowadays. Based on this, visible light communication (VLC) has recently emerged as a viable solution to secure high-speed communications. VLC, a high data rate communication technology, has proven its stature as a promising complementary to its radio frequency (RF) counterpart. VLC is a cost-effective, energy-efficient, and secure technology that exploits the current infrastructure, specifically within indoor and underwater environments. Yet, despite their appealing capabilities, VLC systems face several limitations which constraint their potentials such as LED's limited bandwidth, dimming, flickering, line-of-sight (LOS) requirement, impact of harsh weather conditions, noise, interference, shadowing, transceiver alignment, signal decoding complexity, and mobility issue. Consequently, non-orthogonal multiple access (NOMA) has been considered an effective technique to circumvent these shortcomings. The NOMA scheme has emerged as a revolutionary paradigm to address the shortcomings of VLC systems. The potentials of NOMA are to increase the number of users, system's capacity, massive connectivity, and enhance the spectrum and energy efficiency in future communication scenarios. Motivated by this, the presented study offers an overview of NOMA-based VLC systems. This article provides a broad scope of existing research activities of NOMA-based VLC systems. This article aims to provide firsthand knowledge of the prominence of NOMA and VLC and surveys several NOMA-enabled VLC systems. We briefly highlight the potential and capabilities of NOMA-based VLC systems. In addition, we outline the integration of such systems with several emerging technologies such as intelligent reflecting surfaces (IRS), orthogonal frequency division multiplexing (OFDM), multiple-input and multiple-output (MIMO) and unmanned aerial vehicles (UAVs). Furthermore, we focus on NOMA-based hybrid RF/VLC networks and discuss the role of machine learning (ML) tools and physical layer security (PLS) in this domain. In addition, this study also highlights diverse and significant technical hindrances prevailing in NOMA-based VLC systems. We highlight future research directions, along with provided insights that are envisioned to be helpful towards the effective practical deployment of such systems. In a nutshell, this review highlights the existing and ongoing research activities for NOMA-based VLC systems, which will provide sufficient guidelines for research communities working in this domain and it will pave the way for successful deployment of these systems.
联网实体的增强型增殖需要为下一代无线网络部署创新技术。然而，一个关键问题是频谱稀缺，这是由于当今前所未有的广播渗透率造成的。基于这一点，可见光通信（VLC）最近已成为确保高速通信的可行解决方案。VLC 是一种高速率数据通信技术，已证明其作为射频（RF）对应物的有前途的补充技术的地位。VLC 是一种具有成本效益、节能且安全的技术，可利用当前基础设施，特别是在室内和水下环境中。然而，尽管它们具有吸引人的功能，但 VLC 系统面临着一些限制其潜力的限制，例如 LED 的有限带宽、调光、闪烁、视距（LoS）要求、恶劣天气条件的影响、噪声、干扰、阴影、收发器对准、信号解码复杂性和移动性问题。因此，非正交多址接入（NOMA）已被认为是克服这些缺点的有效技术。NOMA 方案已成为解决 VLC 系统缺点的革命性范例。NOMA 的潜力在于增加用户数量、系统容量、大规模连接，并提高未来通信场景中的频谱和能量效率。受此启发，本研究提供了基于 NOMA 的 VLC 系统概述。本文提供了基于 NOMA 的 VLC 系统现有研究活动的广泛范围。本文旨在提供对 NOMA 和 VLC 重要性的第一手了解，并调查了几种启用 NOMA 的 VLC 系统。我们简要强调了基于 NOMA 的 VLC 系统的潜力和功能。此外，我们概述了这些系统与智能反射面（IRS）、正交频分复用（OFDM）、多输入多输出（MIMO）和无人机（UAV）等几种新兴技术的集成。此外，我们专注于基于 NOMA 的混合 RF/VLC 网络，并讨论了机器学习（ML）工具和物理层安全（PLS）在该领域的作用。此外，本研究还强调了基于 NOMA 的 VLC 系统中存在的各种重大技术障碍。我们强调了未来的研究方向，并提供了预期对该领域研究人员有帮助的见解，这将有助于这些系统的有效实际部署。简而言之，本综述强调了基于 NOMA 的 VLC 系统的现有和正在进行的研究活动，这将为在该领域工作的研究社区提供足够的指导，并为这些系统的成功部署铺平道路。
