  The integration of unmanned aerial vehicles (UAVs) into the terrestrial
cellular networks is envisioned as one key technology for next-generation
wireless communications. In this work, we consider the physical layer security
of the communications links in the millimeter-wave (mmWave) spectrum which are
maintained by UAVs functioning as base stations (BS). In particular, we propose
a new precoding strategy which incorporates the channel state information (CSI)
of the eavesdropper (Eve) compromising link security. We show that our proposed
precoder strategy eliminates any need for artificial noise (AN) transmission in
underloaded scenarios (fewer users than number of antennas). In addition, we
demonstrate that our nonlinear precoding scheme provides promising secrecy-rate
performance even for overloaded scenarios at the expense of transmitting
low-power AN.
