A low-complexity pilot reuse scheme to increase the throughput of massive MIMO

Pilot reuse (PR) in each cell has been proposed to reduce the pilot overhead and improve the throughput of massive multiple-input multiple-output systems. Since PR can introduce interference into channel estimation, several pilot scheduling schemes have been developed to alleviate this problem. However, current schemes have high computational complexity. In this paper, we try to design a low-complexity PR scheme making full use of the channel angle-of-arrival (AOA) information. First we point out that the pilot interference may remain severe even though the AOAs of users reusing pilots are non-overlapping, then an additional criterion is proposed to guide PR. We also develop a method based on the spatial filtering to estimate the channel AOA cosine interval, and develop a PR scheme with the criterion. Simulation results show that the pilot interference can be mainly confined to be a very low level under the proposed PR scheme, and the system throughput can be greatly improved compared to the conventional massive MIMO system.