  In this paper, a full-duplex unmanned aerial vehicle (FD-UAV) relay is
employed to increase the communication capacity of millimeter-wave (mmWave)
networks. Large antenna arrays are equipped at the source node (SN),
destination node (DN), and FD-UAV relay to overcome the high path loss of
mmWave channels and to help mitigate the self-interference at the FD-UAV relay.
Specifically, we formulate a problem for maximization of the achievable rate
from the SN to the DN, where the UAV position, analog beamforming, and power
control are jointly optimized. Since the problem is highly non-convex and
involves high-dimensional, highly coupled variable vectors, we first obtain the
conditional optimal position of the FD-UAV relay for maximization of an
approximate upper bound on the achievable rate in closed form, under the
assumption of a line-of-sight (LoS) environment and ideal beamforming. Then,
the UAV is deployed to the position which is closest to the conditional optimal
position and yields LoS paths for both air-to-ground links. Subsequently, we
propose an alternating interference suppression (AIS) algorithm for the joint
design of the beamforming vectors and the power control variables. In each
iteration, the beamforming vectors are optimized for maximization of the
beamforming gains of the target signals and the successive reduction of the
interference, where the optimal power control variables are obtained in closed
form. Our simulation results confirm the superiority of the proposed
positioning, beamforming, and power control method compared to three benchmark
schemes. Furthermore, our results show that the proposed solution closely
approaches a performance upper bound for mmWave FD-UAV systems.
