Heterogeneous Massive MIMO with Small Cells
A heterogeneous network with Massive MIMO and small cells can achieve even higher spectral and energy efficiency than a Massive MIMO alone. The performance of such heterogeneous system is examined in this paper. A few small cells are used to enhance the spectral and energy efficiency of the overall system. Macro Massive MIMO base stations use a large number of antennas, which enables accurate nulling of small cell users to suppress the interference between macro cell and small cells. We derive analytical expressions for the capacity and SINR lower bounds for both the downlink and uplink of the heterogeneous network. Our simulation results shows that nulling from macro cell Massive MIMO is essential for small cells' good and stable performance.