Ofdma-based Networks Capacity Improvement Using Enhanced Fractional Frequency Reuse Scheme

OFDMA as a broadband technology is intended to offer high data rate services. In cellular networks, a Frequency Reuse (FR) principle has been used to maximize the Signal to Noise-plus-Interference Ratio (SINR), which in turn allows high data rates and spectral efficiency to be achieved. Earlier FR schemes used in 2G and 3G networks are known as Integer Frequency Reuse (IFR) schemes, and were able to improve the global SINR of the system but not the interference at cell edge. Fractional Frequency Reuse (FFR) schemes have been proposed in OFDMA based networks (WiMAX forum 2006) to combat the low SINR at cell edge and gain more amount of spectrum per cell. The tradeoff between interference mitigation using IFR schemes and the extra cell BW gained from FFR scheme needs to be considered. There is a need for the analysis and optimization of FFR key parameters which control the system performance to ensure the highest data rate and spectral efficiency. In this paper, we propose a new FFR-based scheme called Enhance FFR (EFFR), deriving its analytic model and using simulations to evaluate its performance along with different FR schemes and patterns, including IFR and FFR (classified into Hard, HFFR and Soft, SFFR). The effective SINR (SINReff) and Cell Data Rate (DRcell) are used as performance criteria. Further, the optimum values of SINRth and power ration ψ have been defined for all FR patterns. Simulation results show that the highest DRcell was obtained from the proposed EFFR 1x3x3, followed by SFFR 3x1x1, at 137.85 Mbps and 111.33 Mbps, respectively.