  In this paper, the privacy of wireless transmissions is improved through the
use of an efficient technique termed dynamic directional modulation (DDM), and
is subsequently assessed in terms of the measure of information leakage.
Recently, a variation of DDM termed low-power dynamic directional modulation
(LPDDM) has attracted significant attention as a prominent secure transmission
method due to its ability to further improve the privacy of wireless
communications. Roughly speaking, this modulation operates by randomly
selecting the transmitting antenna from an antenna array whose radiation
pattern is well known. Thereafter, the modulator adjusts the constellation
phase so as to ensure that only the legitimate receiver recovers the
information. To begin with, we highlight some privacy boundaries inherent to
the underlying system. In addition, we propose features that the antenna array
must meet in order to increase the privacy of a wireless communication system.
Last, we adopt a uniform circular monopole antenna array with equiprobable
transmitting antennas in order to assess the impact of DDM on the information
leakage. It is shown that the bit error rate, while being a useful metric in
the evaluation of wireless communication systems, does not provide the full
information about the vulnerability of the underlying system.
