  The looming electromagnetic spectrum crisis -- due to the fact of the
explosive growth in the increasing user data demand -- has encouraged the
emergence of new wireless technologies. This paper surveys the state-of-the-art
leading and rapid developments in the current Light Fidelity (LiFi) technology.
First, an overview is shown to help readers understand the potential of this
technology. A comprehensive comparison with legacy wireless technologies is
analyzed. We devise a taxonomy based on the main characteristics such as
modulation techniques, applications, scenarios, network topologies, and
architecture requirements, which enables a foundation for the research
community. We highlight the powerful opportunities, the ongoing works, and
results, identifying the challenges for future research.
