  With the growing interest in cell-free massive multiple-input multiple-output
(MIMO) systems, the benefits of single-antenna access points (APs) versus
multi-antenna APs must be analyzed in order to optimize deployment. In this
paper, we compare various antenna system topologies based on achievable
downlink spectral efficiency, using both measured and synthetic channel data in
an indoor environment. We assume multi-user scenarios, analyzing both conjugate
beamforming (or maximum-ratio transmission (MRT)) and zero-forcing (ZF)
precoding methods. The results show that the semi-distributed multi-antenna APs
can reduce the number of APs, and still achieve the comparable achievable rates
as the fully-distributed single-antenna APs with the same total number of
antennas.
