  In this paper we first derived the mathematical expression for lower bound
spectral efficiency (SE) calculation for zero-force (ZF), and minimum mean
square error (MMSE). Secondly, we calculated the simulation SE with three
algorithms for ZF and MMSE precoding. We compared the simulation and
theoretical results and found that the theoretical results are 1 to 1.5 bits
less than the simulation values which implied that the theoretical lower bounds
are actually the lower bounds. To achieve the maximum spectral efficiency in
downlink massive MIMO systems we assumed perfect CSI, ZF and MMSE precoding in
this paper. We also considered that the channel has the characteristics of
small and large scale fading (SSF and LSF) as the model is like a practical. We
investigated the effect of different SNR, base station (M) and radius (R) of
the cell on spectral efficiency for simulation and theoretical results. We also
evaluated the performance of SE of each algorithms and precoding schemes for
different configurations. From the results we have observed that algorithms-1
and ZF outperform other algorithms and MMSE. From our investigation we noticed
that the LSF parameters are the most dominated factor in SE in massive MIMO
systems.
