OFDMA cellular network with fractional frequency reuse under maximum SIR connectivity

In this paper, we analyze the downlink signal-to-interference ratio (SIR) performance in an OFDMA cellular network where the base-stations (BSs) are distributed according to a homogeneous Poisson point process on the two-dimensional plane. We study two popular adaptive fractional frequency reuse (FFR) mechanisms, namely strict-FFR and soft frequency reuse (SFR). We compute the coverage probability at the mobile-station (MS) which chooses to communicate with the BS with the maximum instantaneous SIR for the two FFR techniques. Comparison of these results with those of the nearest BS connectivity model by Novlan et. al. show a surprising result that the maximum SIR connectivity, which is known to be coverage optimal for static and no frequency reuse scenarios, is not optimal anymore with FFR techniques. This shift from conventional wisdom demands further exploration on which BS should the MS connects to for optimal downlink performance.