The Optimal Distance Threshold of Aerial FFR Systems with Multiple Antennas

Abstract

The distance threshold, which is used to distinguish the cell-edge region from the cell- center region, is an important factor in fractional frequency reuse (FFR) system performance. In this paper, we study the optimal distance threshold to maximize system throughput in the downlink cellular networks including aerial base stations. Subject to the constraint that a given target outage probability is satisfied, the optimal distance threshold is analyzed as a function of cell size. It is proven that when the sizes of all cells in the network are scaled at the same rate, the optimal distance threshold normalized by cell size is non-decreasing in the cell size. The analytical results in this paper provide a system design guideline for initial planning of FFR cellular networks of different sizes including macro, pico, and femto systems. In particular, for size-scalable aerial networks comprising base stations in the sky, such as balloons or unmanned aerial vehicles, our analysis offers insight into the design of the distance threshold with regard to cell size.