  Wireless communications refer to data transmissions in unguided propagation
media through the use of wireless carriers such as radio frequency (RF) and
visible light (VL) waves. The rising demand for high data rates, especially, in
indoor scenarios, overloads conventional RF technologies. Therefore,
technologies such as millimeter waves (mmWave) and cognitive radios have been
adopted as possible solutions to overcome the spectrum scarcity and capacity
limitations of the conventional RF systems. In parallel, visible light
communication (VLC) has been proposed as an alternative solution, where a light
source is used for both illumination and data transmission. In comparison to RF
links, VLC links present a very high bandwidth that allows much higher data
rates. VLC exhibits also immunity to interference from electromagnetic sources,
has unlicensed channels, is a very low power consumption system, and has no
health hazard. VLC is appealing for a wide range of applications including
reliable communications with low latency such as vehicle safety communication.
Despite the major advantages of VLC technology and a variety of its
applications, its use has been hampered by its cons such as its dependence on a
line of sight connectivity. Recently, hybrid RF/VLC systems were proposed to
take advantage of the high capacity of VLC links and better connectivity of RF
links. Thus, hybrid RF/VLC systems are envisioned as a key enabler to improve
the user rates and mobility on one hand and to optimize the capacity,
interference and power consumption of the overall network on the other hand.
This paper seeks to provide a detailed survey of hybrid RF/VLC systems. This
paper represents an overview of the current developments in the hybrid RF/VLC
systems, their benefits and limitations for both newcomers and expert
researchers.
