Coverage Analysis for UAV-Assisted mmWave Cellular Networks Using Poisson Hole Process

To reduce strong mutual interference between unmanned aerial vehicles (UAVs) and ground base stations (GBSs) and to balance the quality of service (QoS) of cell-center and cell-edge users, in UAV-assisted millimeter wave (mmWave) cellular networks we let the UAVs serving as aerial base stations (ABSs) keep a certain distance from the GBSs. It is assumed that GBSs are distributed by a Poisson point process (PPP) on the ground, and the location of UAVs is modeled as a Poisson hole process (PHP) at a certain altitude. Based on the preserving neighbor hole approximation method, the nearest distance distribution functions are derived. With the strongest average received power association policy, we provide the distribution functions of serving distances and the user association probabilities. Then, the coverage probability of the considered network is derived. The coverage performance of two special cases, the mmWave terrestrial cellular network and the UAV-assisted mmWave cellular network with PPP model, are also derived. In addition, the analysis framework is extended into the scenario where UAVs have different altitudes. Through simulations, optimal key ABS parameters maximizing the coverage probability are demonstrated. It also unveils that the proposed UAV-assisted mmWave cellular network can enhance the coverage probability via carefully designing of system parameters.