Fuzzy Logic Based Handover Under Multi-Connectivity in Cellular-Connected UAV Communications

Cellular-connected unmanned aerial vehicle (UAV) communications is a promising solution to enable UAVs' beyond visual line of sight operations. However, most of the current cellular systems may only provide service for the UAV through base station (BS) antennas' sidelobes and thus result in frequent handovers. Ensuring reliable connectivity for such UAV systems is a significant challenge. Introducing multi-connectivity (MC) can reduce data plane interruptions and achieve higher reliability. However, existing works adopting reference signal received power (RSRP)-based handover in MC may not be ideal in cellular-connected UAV communications. In this paper, we therefore propose a multi-criteria handover scheme under MC based on fuzzy logic (FL) to reduce the handover rate and provide more reliable communications for cellular-connected UAVs. First, we consider the average RSRP, the average change rate in RSRP, and the average BS loads as the multiple handover criteria. Then, we adopt FL to combine the considered multiple criteria and obtain the scores for each BS. Finally, we update the serving BS set according to the scores of each BS. Simulation results show that the proposed handover scheme can significantly reduce the handover rate, and provide more reliable connectivity and higher throughput.