Energy-Efficient UAV-Assisted Communication with Spectrum Optimization

In traditional ground cellular systems, ground terminals (GTs) in marginal areas are often faced with performance bottlenecks due to they are too far from the macro base station (MBS). For some temporary and unexpected communication service requirements, it is uneconomical to deploy femtocell access points (FAPs) on the edge of cell. In this paper, we investigate a cellular system that utilizes a unmanned aerial vehicles (UAVs) with base station module unit as an airborne mobile base station to provide communication channel for the cell-edge users offloaded by the MBS. Compared with FAPs, UAV is cheaper and flexible which can provide better communication quality for the cell-edge GTs with better channel condition. Based on the theoretical model, we proposed plausible optimal algorithm to maximize the energy-efficiency (EE) of the UAV by jointly optimizing the spectrum allocation, flying speed and user partition between the UAV and MBS. Numerical results indicate that our design could achieve relatively higher energy-efficiency by exploiting optimal flight strategy and spectrum allocation strategy.