User Grouping and Pilot Allocation for Spatially Correlated Massive MIMO Systems

This paper proposes a novel approach to deal with pilot contamination for spatially correlated massive multiple-input multiple-output (MIMO) systems with insufficient pilots. Specifically, a typical multi-cell multi-terminal time division duplex massive MIMO system is modeled first. To maximize the average achievable system capacity, a user grouping method which progressively merges the individual terminals with the largest angle of arrival similarity is proposed to mitigate the intra-cell interference. Furthermore, in order to alleviate the inter-cell interference, a pilot allocation method is proposed, including two algorithms, i.e., group matching algorithm and graph coloring-based pilot allocation algorithm. Compared with the existing pilot allocation schemes, the simulation results validate that the proposed approach can effectively improve the complexity-performance trade-off with a finite number of the base station antennas.