  A full-duplex (FD) multiple antenna access point (AP) communicating with
single antenna half-duplex (HD) spatially random users to support simultaneous
uplink (UL)/downlink (DL) transmissions is investigated. Since FD nodes are
inherently constrained by the loopback interference (LI), we study precoding
schemes for the AP based on maximum ratio combining (MRC)/maximal ratio
transmission (MRT), zero-forcing and the optimal scheme for UL and DL sum rate
maximization using tools from stochastic geometry. In order to shed insights
into the system's performance, simple expressions for single antenna/perfect LI
cancellation/negligible internode interference cases are also presented. We
show that FD precoding at AP improves the UL/DL sum rate and hence a doubling
of the performance of the HD mode is achievable. In particular, our results
show that these impressive performance gains remain substantially intact even
if the LI cancellation is imperfect. Furthermore, relative performance gap
between FD and HD modes increases as the number of transmit/receive antennas
becomes large, while with the MRC/MRT scheme, increasing the receive antenna
number at FD AP, is more beneficial in terms of sum rate than increasing the
transmit antenna number.
