  Communications based solely on radio frequency (RF) networks cannot provide
adequate quality of service for the rapidly growing demands of wireless
connectivity. Since devices operating in the optical spectrum do not interfere
with those using the RF spectrum, wireless networks based on the optical
spectrum can be added to existing RF networks to fulfill this demand. Hence,
optical wireless communication (OWC) technology can be an excellent complement
to RF-based technology to provide improved service. Promising OWC systems
include light fidelity (LiFi), visible light communication, optical camera
communication (OCC), and free-space optical communication (FSOC). OWC and RF
systems have differing limitations, and the integration of RF and optical
wireless networks can overcome the limitations of both systems. This paper
describes an LiFi/femtocell hybrid network system for indoor environments. Low
signal-to-interference-plus-noise ratios and the shortage bandwidth problems of
existing RF femtocell networks can be overcome with the proposed hybrid model.
Moreover, we describe an integrated RF/optical wireless system that can be
employed for users inside a vehicle, remote monitoring of ambulance patients,
vehicle tracking, and vehicle-to-vehicle communications. We consider LiFi, OCC,
and FSOC as the optical wireless technologies to be used for communication
support in transportation, and assume macrocells, femtocells, and wireless
fidelity to be the corresponding RF technologies. We describe handover
management-including detailed call flow, interference management, link
reliability improvement, and group handover provisioning-for integrated
networks. Performance analyses demonstrate the significance of the proposed
integrated RF/optical wireless systems.
