Coverage Analysis for CellularConnected UAVs with 3D Antenna Patterns In this paper, we consider cellularconnected unmanned aerial vehicle (UAV) networks, in which the UAVs are aerial user equipments (UEs) served by the ground base stations (GBSs). A realistic groundtoair channel model, with line of sight (LOS) and nonLOS (NLOS) transmissions, is incorporated into the analysis. Three dimensional (3D) antenna radiation combing the vertical and horizontal patterns is taken into account for the GBSs. More importantly, 3D antenna patterns are also considered for the UAVs. In particular, we compare the performances of four types of antenna configurations, namely an omnidirectional pattern, a doughnutshaped sine pattern, a doughnutshaped cosine pattern, a directional pattern with tilting angle toward the serving GBS. Via numerical results, it is demonstrated that the directional pattern with tilting angle provides the best signaltointerferenceplusnoise ratio (SINR) coverage probability. It is also shown that the optimal UAV altitude varies depending on the environment and antenna patterns.

EnergyEfficient UAVAssisted 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 celledge users offloaded by the MBS. Compared with FAPs, UAV is cheaper and flexible which can provide better communication quality for the celledge GTs with better channel condition. Based on the theoretical model, we proposed plausible optimal algorithm to maximize the energyefficiency (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 energyefficiency by exploiting optimal flight strategy and spectrum allocation strategy.