Deployment Optimization of UAV Relay for Malfunctioning Base Station: Model-Free Approaches

Due to the advantages of high mobility, high maneuverability and high probability of line of sight (LoS) transmission, unmanned aerial vehicles (UAVs) have attracted much interest in assisting wireless communication systems. This paper considers a set of ground users cannot receive service from the base station because of a sudden base station malfunction, a UAV is deployed in the air to work as a relay to establish communication links between uncovered users and the neighboring base station. We are going to optimize the UAV relay deployment, aiming to maximize the capacity of the relay network. Considering the channel model and exact positions of ground users are priori unknown, the problem of deployment optimization can't be solved directly because of lacking parameters. Thus, considering multiple detecting UAVs are available and only one is available, model-free online deployment approaches are respectively proposed to solve this challenging problem. The optimal relay deployment is acquired via online learning and iteration without the knowledge of channel model and exact positions of the users but with the real-time measurement of relay capacity, thus the proposed model-free deployment approaches can be adaptive to the practical communication environment compared to the model-based optimization. Simulation results show that with the proposed model-free deployment approaches, relay network capacities are close to the optimum.