  The transmission capacity of an ad-hoc network is the maximum density of
active transmitters per unit area, given an outage constraint at each receiver
for a fixed rate of transmission. Assuming that the transmitter locations are
distributed as a Poisson point process, this paper derives upper and lower
bounds on the transmission capacity of an ad-hoc network when each node is
equipped with multiple antennas. The transmitter either uses eigen multi-mode
beamforming or a subset of its antennas to transmit multiple data streams,
while the receiver uses partial zero forcing to cancel certain interferers
using some of its spatial receive degrees of freedom (SRDOF). The receiver
either cancels the nearest interferers or those interferers that maximize the
post-cancelation signal-to-interference ratio. Using the obtained bounds, the
optimal number of data streams to transmit, and the optimal SRDOF to use for
interference cancelation are derived that provide the best scaling of the
transmission capacity with the number of antennas. With beamforming, single
data stream transmission together with using all but one SRDOF for interference
cancelation is optimal, while without beamforming, single data stream
transmission together with using a fraction of the total SRDOF for interference
cancelation is optimal.
