  This paper examines the secrecy performance of millimeter-wave (mm-Wave)
communications with imperfect hardware and uncertain eavesdropper location. We
consider a multiple-antenna source communicating with a single-antenna
destination using masked beamforming to transmit the information signals with
artificial noise (AN) in the presence of a passive eavesdropper (Eve). For this
system, we derive new expressions for the secrecy outage probability (SOP) and
secrecy throughput with mm-Wave multipath propagation under slow-fading channel
conditions and hardware imperfections. Based on this, optimal power allocation
(OPA) solutions are derived for the information and AN signals aimed at
minimizing the SOP and maximizing the secrecy throughput. Our results reveal
that it is non-trivial to achieve an OPA solution for the general scenario of
imperfect hardware. We also highlight that our proposed masked beamforming with
OPA scheme significantly enhances the secrecy throughput compared with the
benchmark schemes of maximal-ratio transmission and equal power allocation.
