Fractional Frequency Reuse (FFR) Scheme for Inter-Cell Interference (ICI) Mitigation in Multi-Relay Multi-Cell OFDMA Systems

In next-generation wireless networks, high data rates, improvement of Spectral Efficiency (SE), meeting the Quality of Service (QoS) requirements, increasing Energy Efficiency (EE), reducing cost, and lower complexity of cellular networks systems have become essential design metrics. Use of resource allocation and interference mitigation techniques achieve these targets, especially for users located in the cell edge region. FFR schemes with relays are used to minimize the impact of ICI in Orthogonal Frequency Division Multiple Access (OFDMA) cellular networks and to enhance the QoS. The frequency patterns (sets) in the FFR scheme are designed such that the interference from adjacent cells is minimized. Instead of using the cell system with Frequency Reuse Factor (FRF) of 1 TRF \pmb=1), FRF \pmb=3, and FRF \pmb=(1,3), this paper proposes new frequency patterns for FRF \pmb=(1,7/3) using (7,3,1) difference set and FRF \pmb=(1,7/4) using (7,4,2) difference set to provide an enhancement of the system performance in terms of SE, EE, Signal-to-Interference plus Noise Ratio (SINR), Cumulative Distribution Function (CDF) of SINR of the received signal, and Outage Probability (OP). Simulation results show that the proposed schemes have more significant ICI reduction for cell edge users compared to those of previous work.