Low-complexity AoA-driven pilot assignment for multi-cell massive MIMO systems

Abstract In this paper, the problem of pilot contamination in a multi-cell massive multiple input multiple output (MIMO) system is addressed. We propose a pilot assignment scheme, in which compared to the conventional methods, the corresponding optimization problem is solved in a low-complexity manner. To this end, by utilization of multi-path model comprising angle of arrival (AoA) distributions of users for propagation channels, the pilot assignment pattern would be defined by an optimization problem with discrete variables, and a criterion is presented to realize the obtained problem via an alternative involving continuous optimization variables. In addition, the resultant problem is dealt with in an iterative manner, where the sequential convex programming (SCP) is exploited. The numerical analysis reveals that the proposed method converges by only limited iterations. Furthermore, the proposed scheme out-performs compared to the conventional methods from complexity point of view, for a negligible degradation in the uplink sum rate.