Improved Pilot Sequences Allocation in Massive MIMO Systems

Pilot contamination is one of the main limiting factors for the performance of massive MIMO systems. In this paper, two novel pilot allocation schemes are proposed to mitigate the pilot contamination effect and to enhance the system performance with low complexity of pilot allocation. The pilot assignment schemes are based on dividing the cell into center and edge zones, including uniform N sectors in the edge zone. The overall spectral efficiency of the proposed schemes is maximized over the ratio of center zone radius to the cell radius and the number of scheduled users per cell. Numerical results reveal that the proposed schemes significantly outperform the existing techniques in terms of mitigating the pilot contamination and the spectral efficiency improvement.