  Fractional frequency reuse (FFR) is an interference management technique
well-suited to OFDMA-based cellular networks wherein the cells are partitioned
into spatial regions with different frequency reuse factors. To date, FFR
techniques have been typically been evaluated through system-level simulations
using a hexagonal grid for the base station locations. This paper instead
focuses on analytically evaluating the two main types of FFR deployments -
Strict FFR and Soft Frequency Reuse (SFR) - using a Poisson point process to
model the base station locations. The results are compared with the standard
grid model and an actual urban deployment. Under reasonable special cases for
modern cellular networks, our results reduce to simple closed-form expressions,
which provide insight into system design guidelines and the relative merits of
Strict FFR, SFR, universal reuse, and fixed frequency reuse. We observe that
FFR provides an increase in the sum-rate as well as the well-known benefit of
improved coverage for cell-edge users. Finally, a SINR-proportional resource
allocation strategy is proposed based on the analytical expressions, showing
that Strict FFR provides greater overall network throughput at low traffic
loads, while SFR better balances the requirements of interference reduction and
resource efficiency when the traffic load is high.
