A survey of optical wireless technologies: practical considerations, impairments, security issues and future research directions.

In the past few decades, the academic research and industrial synergy is dramatically accelerating to conceptualize high data rate services. The congestion in the radio frequency (RF) spectrum has imposed many inherent limitations in the growth of future wireless networks. These limitations have spurred global research activities to open new parts of the electromagnetic wave spectrum. More researches and developments in new modulation schemes, channel modelling and signal processing techniques are yet to be explored. Optical wireless communication (OWC) has appeared as an emerging complementary technology to RF systems. It is deemed as a promising alternative to address RF spectrum congestion and enhance system's capacity. OWC has gained widespread attention due to its high confidentiality, large spectrum resources and strong resistance to electromagnetic interference (EMI). In this paper, we envisage OWC systems as a promising solution for the bandwidth shortage of RF spectrum. We have also discussed the current upsurge of diversified OWCs in fifth generation (5G) and Internet-of-Things (IoT) solutions which has spurred heated discussion for future technologies. In this study, we have outlined a holistic vision of several OWC enabling technologies and survey of potential issues in OWC systems. We investigate visible light communication (VLC) and free space optics (FSO) as potential implementation approaches for OWC systems. Generally, the intent of this extant study includes (i) potential features and classifications of OWC systems, (ii) key enabling technologies, (iii) link design requirements and modulation schemes, (iv) main impairments and solutions to reduce the impairments, and (v) security issues and techniques to secure OWC. At last, open research challenges and future research directions in OWC systems are investigated. In this regard, we believe this survey will be helpful to aggregate the research efforts and eliminate the technical uncertainties towards breakthrough novelties of OWC technologies. [ABSTRACT FROM AUTHOR]