  The presence of a super high rate, but also cost-efficient, easy-to-deploy,
and scalable, backhaul/fronthaul framework is essential in the upcoming
fifth-generation (5G) wireless networks \& beyond. Motivated by the mounting
interest in the unmanned flying platforms of various types including unmanned
aerial vehicles (UAVs), drones, balloons, and
high-altitude/medium-altitude/low-altitude platforms (HAPs/MAPs/LAPs), which we
refer to as the networked flying platforms (NFPs), for providing communications
services and the recent advances in free-space optics (FSO), this article
investigates the feasibility of a novel vertical backhaul/fronthaul framework
where the NFPs transport the backhaul/fronthaul traffic between the access and
core networks via point-to-point FSO links. The performance of the proposed
innovative approach is investigated under different weather conditions and a
broad range of system parameters. Simulation results demonstrate that the
FSO-based vertical backhaul/fronthaul framework can offer data rates higher
than the baseline alternatives, and thus can be considered as a promising
solution to the emerging backhaul/fronthaul requirements of the 5G+ wireless
networks, particularly in the presence of ultra-dense heterogeneous small
cells. The paper also presents the challenges that accompany such a novel
framework and provides some key ideas towards overcoming these challenges.
