Analysis and Comparison of Fractional Frequency Reuse Schemes Based on Worst Case Signal to Interference Power Ratio in OFDMA Uplink

摘要

Fractional Frequency Reuse (FFR) is an efficient interference mitigation technique for modern cellular networks due to its low complexity, low 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 power Ratio (SIR) for three main FFR schemes strict FFR, Soft FFR, and sectored FFR. A closed form expression is derived analytically for worst SIR, and best inner radius. This analytical technique is utilized to configure a FFR solution for the uplink of Orthogonal Frequency Division Multiple Access (OFDMA) cellular systems. The analysis is performed using two- tiers cellular network with uniform user density and for three different cases of FFR, where Frequency Reuse Factor (FRF)= 3, FRF= 4, and Soft Frequency Reuse (SFR). Also the effect of power control exponent on both FFR schemes is 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. Power control exponent does not affect FFR with reuse three but strongly affects SFR and FRF= 4 as its increase reduces its SIR and inner radius.