Massive MIMO versus Small-Cell Systems: Spectral and Energy Efficiency Comparison

In this paper, we study the downlink performance of two important 5G network architectures, i. e. massive multipleinput multiple-output (M-MIMO) and small-cell densification. We propose a comparative modeling for the two systems, where the user and antenna/ base station (BS) locations are distributed according to Poisson point processes (PPPs). We then study the SIR distribution and the outage rate of each network. By comparing these results, we observe that for user-average spectral efficiency, small-cell densification is favorable in crowded areas with moderate to high user density and M-MIMO with low user density. However, small-cell systems outperform M-MIMO in all cases when the performance metric is the energy efficiency. The results of this paper are useful for the optimal design of practical 5G networks.