  Space Division Multiple Access (SDMA) based Medium Access Control (MAC)
protocols have been proposed to enable concurrent communications and improve
link throughput in Multi-Input Multi-Output (MIMO) Ad Hoc networks. For the
most part, the works appearing in the literature make idealized and simplifying
assumptions about the underlying physical layer as well as some aspects of the
link adaptation protocol. The result is that the performance predicted by such
works may not necessarily be a good predictor of actual performance in a fully
deployed system. In this paper we look to introduce elements into the SDMA MAC
concept that would allow us to better predict their performance under realistic
operating conditions. Using a generic SDMA-MAC we look at how the network sum
throughput changes with the introduction of the following: $(a)$ use of the
more practical MMSE algorithm instead of the zero-forcing or SVD based nulling
algorithms used for receive beamnulling; $(b)$ impact of channel estimation
errors; $(c)$ introduction of link adaptation mechanism specifically designed
for concurrent SDMA MACs; $(d)$ incorporation of TX beamforming along with RX
beamnulling. Following on the transmission window during which concurrent
transmissions are allowed by the MAC, we qualify the impact of each of these
four elements in isolation. At the conclusion, the performance of a system that
incorporates elements $a-d$ is presented and compared against the baseline
system, showing an improvement of up to 5x in the overall network sum
throughput.
