Abstract:

To tackle the pilot contamination (PC) problem in three-dimensional (3D) massive multiple-input multiple-output (MIMO) systems, a soft pilot reuse (SPR) based pilot contamination suppression scheme is proposed. By exploiting the elevation degree of freedom (DoF), the users with separable or inseparable elevation channel state information (CSI) among the adjacent cells are regarded as center users or edge users, respectively. The edge users in the adjacent cells are assigned orthogonal pilot sequences to eliminate the PC, while the center users in all cells reuse the pilot sequences and suppress the PC by the improved channel estimate method. Thus, the channel estimation accuracy of all the users in the cell can be improved. Simulation results demonstrate that, compared to the conventional pilot allocation schemes, the proposed scheme can decontaminate pilots more effectively and achieve a better system performance with a low complexity.

Key words: three-dimensional massive multiple-input multiple-output, pilot contamination, soft pilot reuse, channel estimate