Performance analysis of uplink Fractional Frequency Reuse using worst case Signal to Interference Ratio

Fractional Frequency Reuse (FFR) is an efficient mitigation technique for modern cellular networks because of its low complexity and coordination requirements and resource allocation flexibility. This work considers the use of FFR in the cellular uplink where we analyze the uplink worst case Signal to Interference Ratio (SIR) for two main FFR schemes; which are strict FFR and Soft FFR. A closed form expression is derived analytically for the worst SIR and for the best inner radius. This analytical technique is utilized to configure a FFR solution for the uplink of OFDMA cellular system. The analysis is performed using two-tier cellular network with uniform user density and for three different cases of FFR. The effect of power control exponent on both FFR schemes is also studied. The inner radius configuration depends on equalizing the worst SIR for both inner and outer edges of the cell. Numerical results show that FFR with reuse four yields the highest SIR. It is noticed that power control exponent doesn´t affect strict FFR but affects SFR as it reduces its SIR and inner radius.