FSO-Based Vertical Backhaul/Fronthaul Framework for 5G+ Wireless Networks

Abstract

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.Index Terms-Free-space optics (FSO); 5G+ wireless networks; vertical backhaul/fronthaul; heterogeneous networks (HetNets); radio access network (RAN); networked flying platforms (NFPs); unmanned aerial vehicle (UAV); drones; low altitude platform (LAP); medium altitude platform (MAP); high altitude platform (HAP); link budget.

A Key 6G Challenge and Opportunity - Connecting the Remaining 4 Billions: A Survey on Rural Connectivity

“…The main limitation is the cost of civil works, which are generally much more expensive than the cable cost. Although the installation costs can reach 200 USD/meter in dense urban areas [28], they go down to 30 USD/meter in rural areas, as noted in [29]. This clearly plays in favor of fiber deployment when severe geographical constraints do not exist.…”

“…In urban areas, the microwave equipment can be placed on poles or the rooftops of existing buildings. In this case, the pole leasing costs should be taken into account in OPEX calculations [28]. However, in long backhaul stretches traversing non-populated areas in order to reach remote rural agglomerations, appropriate towers need to be built.…”

“…Since microwave frequencies are licensed, appropriate fees should be regularly paid. Instead of considering spectrum costs per capita as in [28], which is more suitable for urban areas, a cost per link seems more appropriate for low density rural areas, in line with the cost presented in [35], since the investigated rural scenario corresponds to a sparsely populated area. In Section III, we the costs for different microwave separation distances between towers: 3, 5, and 10 km.…”

“…In the cost analysis of Section III, we assume a maintenance cost comparable to that of microwave links (considered to be 375 USD/year in [28]) and add an increase of 33% to account for the additional complexity of the equipment, such that the total becomes 500 USD/year. FSO links for satellite communication have also received attention in the literature.…”

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