  In this paper we examine a number of deployment issues which arise from
practical considerations in massive multiple-input-multiple-output (MIMO)
systems. We show both spatial correlation and line-of-sight (LOS) introduce an
interference component to the system which causes non-orthogonality between
user channels. Distributing the antennas into multiple clusters is shown to
reduce spatial correlation and improve performance. Furthermore, due to its
ability to minimize interference, zero forcing (ZF) precoding performs well in
massive MIMO systems compared to matched filter (MF) precoding which suffers
large penalties. However, the noise component in the ZF signal-to-noise-ratio
(SNR) increases significantly in the case of imperfect transmit channel state
information (CSI).
