  In this paper, we consider two fundamental full-duplex (FD) architectures,
two-node and three-node, in the context of cellular networks where the
terminals employ directional antennas. The simultaneous transmission and
reception of data in non-orthogonal channels makes FD radio a potential
solution for the currently limited spectrum. However, its implementation
generates high levels of interference either in the form of loopback
interference (LI) from the output to the input antenna of a transceiver or in
the form of co-channel interference in large-scale multicell networks due to
the large number of active links. Using a stochastic geometry model, we
investigate how directional antennas can control and mitigate the co-channel
interference. Furthermore, we provide a model which characterizes the way
directional antennas manage the LI in order to passively suppress it. Our
results show that both architectures can benefit significantly by the
employment of directional antennas. Finally, we consider the case where both
architectures are employed in the network and derive the optimal values for the
density fraction of each architecture which maximize the success probability
and the network throughput.
