Radio Propagation Environment Prediction Method for UAV-Assisted Cellular Networks with Millimeter-Wave Beamforming

This paper considers an unmanned aerial vehicle (UAV)-assisted millimeter-wave cellular network system. This system can provide a high frequency communication area around a user equipment (UE) by moving a relay station (RS) mounted on the UAV to an appropriate position and relaying signals. The RS communicates with the UE and a base station using narrow beams to compensate for large propagation loss in high frequency bands. Accurate prediction of the propagation environment is important for determining where to move the UAV-RS in this system. Therefore, we propose a radio propagation prediction method that utilizes received power information for multiple beams. The proposed method estimates the propagation conditions and parameters for measurement data by considering not only the relationship between distance and received power but also the power ratio between the beams. Subsequently, a blockage map indicating where a signal is blocked is constructed based on the estimated results. The propagation condition and the channel gain at a given position pair can be predicted using the estimated parameters and the constructed blockage map. Computer simulation results, assuming an urban environment, demonstrate that the proposed method can accurately predict the propagation environment even when there is a large variation in the received power.