Fractional frequency reuse aided pilot decontamination for massive MIMO systems

Pilot contamination leads to a dramatic performance loss in massive multiple-input multiple-output (MIMO) systems. In this paper, we propose an advanced- fractional frequency reuse scheme for massive MIMO systems to tackle the pilot contamination problem. We optimize the size of a cell-center region (CCR) to maximize the average throughput of the system without compromising the data rate of cell-edge users. After simplifying the problem with a lower bound of average throughput, we obtain a low complexity suboptimal solution. By analyzing this solution, we show the relationship between the size of the CCR and the number of antennas at each base station. Simulations results validate our analysis and demonstrate that the proposed scheme outperforms existing method employed in the unity frequency reuse system.