Free Space Optics for 5G Backhaul Networks and Beyond

Abstract

The exponential increase of mobile users and the demand for high-speed data services has resulted in signi cant congestions in cellular backhaul capacity. As a solution to satisfy the tra c requirements of the existing 4G network, the 5G net- work has emerged as an enabling technology and a fundamental building block of next-generation communication networks. An essential requirement in 5G backhaul networks is their unparalleled capacity to handle heavy tra c between a large number of devices and the core network. Microwave and optic ber technologies have been considered as feasible solutions for next-generation backhaul networks. However, such technologies are not cost e ective to deploy, especially for the backhaul in high-density urban or rugged areas, such as those surrounded by mountains and solid rocks. Addi- tionally, microwave technology faces alarmingly challenging issues, including limited data rates, scarcity of licensed spectrum, advanced interference management, and rough weather conditions (i.e., rain, which is the main weather condition that a ects microwave signals the most). The focus of this work is to investigate the feasibility of using free-space-optical (FSO) technology in the 5G cellular backhaul network. FSO is a cost-e ective and wide-bandwidth solution as compared to traditional backhaul solutions. However, FSO links are sensitive to atmospheric turbulence-induced fad- ing, path loss, and pointing errors. Increasing the reliability of FSO systems while still exploiting their high data rate communications is a key requirement in the de- ployment of an FSO backhaul network. Overall, the theoretical models proposed in this work will be shown to enhance FSO link performance.

In the experimental direction, we begin by designing an integrated mobile FSO system. To the best of our knowledge, no work in the literature has addressed the atmospheric path loss characterization of mobile FSO channels in a coastal envi- ronment. Therefore, we investigate the impact of weather e ects in Thuwal, Saudi Arabia, over FSO links using outdoor and indoor setups. For the indoor experiments, results are reported based on a glass climate chamber in which we could precisely control the temperature and humidity.