Mobility Dependent Hybrid RF/FSO Backhaul in UAV Assisted Cellular Networks

The increasing trend of employing unmanned air vehicles (UAVs) as movable base stations (MBSs) holds a great potential of enhancing the performance of a cellular network at a cell edge. The performance is generally enhanced to either accommodate more users or to optimize the throughput of existing ones. One of the paramount challenges of deploying an MSB-based cellular network is to design a stable backhaul connection of the MBS with the ground base station (BS). This paper proposes a hybrid backhaul based on radio frequency (RF) and free space optical (FSO) communication, where the decision to choose between RF and FSO depends on mobility of the MBS. In particular, an analytical framework to model the mobility of a MBS is proposed wherein the probability to fly or to stop is estimated. In addition, analytical expressions for the bit error rate (BER) of RF-only backhaul, FSO-only backhaul and mobility-dependent hybrid RF/FSO backhaul are derived and substantiated through Monte Carlo simulation results.