UAV-Aided Cellular Offloading: A Potential Solution to Hot-Spot Issue in 5G

In conventional terrestrial cellular networks, mobile terminals (MTs) at the cell edge often pose the performance bottleneck due to their long distances from the serving ground base station (GBS), especially in hotspot period when the GBS is heavily loaded. This paper proposes a new hybrid network architecture by leveraging the use of unmanned aerial vehicle (UAV) as an aerial mobile base station, which flies cyclically along the cell edge to serve the cell-edge MTs and help offload data traffic from the GBS. We aim to maximize the minimum throughput of all MTs in the cell, by jointly optimizing the UAV’s trajectory, as well as the bandwidth allocation and user partitioning between the UAV and GBS. We first consider orthogonal spectrum sharing between the UAV and GBS, and then extend to the spectrum reuse case where the total bandwidth is used by both the GBS and UAV with their mutual interference effectively avoided. Numerical results show that the proposed hybrid network with optimized spectrum sharing and cyclical multiple access design significantly improves the spatial throughput over the conventional GBS-only network; while the spectrum reuse scheme can provide further throughput gains compared to orthogonal spectrum sharing, at the cost of more complexity for interference control.