Inter-Tier Interference Coordination in Massive-MIMO System based on Statistical Channel Information

We study the interference coordination in massive-MIMO heterogeneous network. In this scene, macro-users (MUEs) are distributed in clusters and pico-cells are separated from MUEs. There exists the inter-tier interference and it is hard to implement interference coordination since the instantaneous channel state information (CSI) between macro-base station (MBS) and pico-users (PUEs) is hard to obtain. In this circumstance, we propose a two-tier precoding method based on the statistical CSI between MBS and pico-base station (PBS) with the minimum mean square error (MMSE) criterion to form deeper nulling for pico-cells close to MBS. In our method, the outer precoder is designed to mitigate the inter-cluster and the inter-tier interference, and the inner precoder aims to suppress the intra-cluster interference. Simulation results show that our statistical CSI based on the MMSE precoding scheme could mitigate the inter-tier interference efficiently in channels with small spatial angular spread. The proposed method could achieve better throughput than other precoding methods for PUEs close to MBS.