Cell Range Expansion in Backhaul Capacity Limited Massive MIMO HetNets

In this paper, we consider the small cell range expansion problem in massive multiple-input multiple-output (MIMO) heterogeneous networks (HetNets) with limited backhaul capacity, and derive the close-form formulas to calculate the range expansion bias (REB) of equal uplink received signal strengths (RSSs) boundary (EUB). In order to reduce the effect of severe downlink intercell interference in the expanded regions (ERs) of small cell, we propose a downlink precoding scheme based on the estimated channel state information (CSI). Simulation results verify the relationships among different small cell coverage boundaries, and demonstrate the benefits of the proposed downlink precoding scheme in maximizing the overall sum rate and improving the performance of MIMO HetNets.