An Enhanced Handover Scheme for Cellular-Connected UAVs

In this paper, we propose an enhanced handover scheme for cellular-connected UAVs. Specifically, our handover scheme considers the following characteristics: 1) UAV can detect multiple cells with the comparable RSRP levels which may cause many unnecessary handovers. The handover event trigger parameters in our scheme are dynamically adjusted to avoid a UAV to handover from a cell to another cell with the comparable RSRP level; 2)In the process of taking off, the UAV would fly through the null space of antenna lobes many times, while the time duration is normally very short. The RSRP during the UAV taking off varies quickly, so that the measurement reports may not provide an accurate channel information for the UAV. In this case, when the link quality between the UAV and the BS is below a threshold, the BS allows the link being maintained for a while with the hope that the link quality would get better again. We implement our proposed handover scheme on the NS3 platform, and compare with the current LTE handover scheme and the sojourn time estimation-based handover algorithm. Our simulation results demonstrate that our proposed scheme can significantly reduce the number of unnecessary handovers. Moreover, the network throughput of our scheme is improved, since the the communication resources taken by the unnecessary handovers is utilized by the UAV for transmitting data.