The presence of a high-rate, but also cost-efficient and scalable, backhaul/fronthaul framework is essential in the upcoming fifth-generation (5G) wireless networks & beyond to facilitate the anticipated explosive growth in the number of various types of small cells and other RAN (radio access network) technologies, such as distributed antenna systems. Motivated by the mounting interest in Unmanned Aerial Vehicles (UAVs) 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 UAVs, flying at a relatively lower altitude in comparison with commercial flights, 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 system parameters. Simulation results demonstrate that the FSO-based vertical backhaul/fronthaul framework offers data rates higher than the baseline alternatives at competing cost levels, and thus can be considered as a promising cost-effective and scalable solution to the emerging backhaul/fronthaul requirements of the 5G+ wireless networks, particularly in the presence of ultra-dense heterogeneous small cells. We also present the challenges that accompany such a framework and provide some key ideas toward overcoming such challenges.
['Mohamed Alzenad', 'Muhammad Zeeshan Shakir', 'Halim Yanikomeroglu', 'Mohamed-Slim Alouini']
FSO-based Vertical Backhaul/Fronthaul Framework for 5G+ Wireless Networks