Flight Direction-Based Handover in Cellular-Connected UAV Communications

Cellular-connected unmanned aerial vehicle (UAV) communication is a key solution to allow UAV to be connected far beyond the normal point-to-point line of sight range. However, with the down-tilted base station (BS) antennas in most current cellular systems, the UAVs may be served by the sidelobes with a high probability and suffer significant handover delay. It is challenging to provide seamless low latency connectivity for such UAV systems. In this paper, we propose a flight direction-based handover scheme in cellular-connected UAV communications to reduce the handover rate. Specifically, the 'flight angle' of the UAV is reflected in the change rate of reference signal received power (RSRP). When the handover triggering condition is met during the time to trigger (TTT), we adopt the long short-term memory (LSTM) network to predict the RSRP in future slots. Then, the change rate in RSRP and the RSRP threshold can be used to make the handover decision. Simulation results show that the proposed handover scheme can significantly reduce the handover rate with a relatively small drop in RSRP, especially in the case of larger antenna arrays.