Relay selection and link scheduling in cooperative free-space optical backhauling of 5G small cells

With the explosive growth in the number of various small cells in the forthcoming fifth-generation (5G) wireless networks, it is a great challenge to schedule the 5G backhaul traffic in an effective way. In this paper, we investigate the feasibility of a 5G backhaul framework based on Free-Space Optical (FSO) communication system to design a high-rate, but also reliable and resource-efficient backhaul solution. We focus on the problem of throughput maximization in the cooperative FSO relay channel and propose a relay selection algorithm using back-pressure theory to boost transmission quality. Then, a link scheduling algorithm is further put forward to improve the resource utilization by making full use of the idle FSO links. Simulation results demonstrate that the proposed algorithms can significantly enhance the performance of cooperative FSO-backhaul system in reliability and resource utilization, especially for data-intensive transmission scenarios.