Handover Analysis in Aerial Base Station Networks With Different Altitudes

This letter studies the handover characteristics of a network of aerial base stations (ABSs) with different altitudes. In many real-world applications, ABSs fly at different altitudes depending on their tasks or environments. However, to date, the impacts of 3D placement on the handover performance, such as the difference in altitudes or the minimum and maximum altitudes, have not been clarified. We model the locations of ABSs with a 3D Poisson point process and consider two mobility scenarios where either users or ABSs move. We first show the equivalence of the occurrence processes of handovers in different scenarios. We then derive the handover rate per unit length (HOL), which is the expected number of handovers performed during the time a user or ABS moves a unit length. We also derive computationally efficient upper bounds of the HOL and demonstrate that are fairly accurate approximations through numerical examples.