Optimal design parameters for coverage probability in fractional frequency reuse and soft frequency reuse

In this work, the authors derive the optimal signal-to-interference-ratio (SIR) thresholds S_t which maximise coverage probability for both fractional frequency reuse (FFR) and soft frequency reuse (SFR) networks with base station locations modelled using Poisson point process. It is analytically shown that for both FFR and SFR, the optimal SIR threshold is equal to the target SIR T, i.e, S_t = T. The authors also show that at the optimal SIR threshold, FFR achieves a higher coverage than frequency reuse (1/Δ). Furthermore, for the cases when S_t > T and S_t <; T, FFR achieves a higher coverage than reuse (1/Δ) and reuse 1, respectively. On the other hand, SFR coverage can be higher or lower than reuse (1/Δ) coverage, even when S_t = T. However, when S_t > T, SFR achieves a higher coverage than reuse 1, and when S_t <; T, the SFR coverage can be lower than reuse 1 coverage. The FFR and SFR coverages are also compared for a given Δ, and it is shown that FFR achieves a higher coverage than SFR at the optimal value of S_t.