  Millimeter wave (mmWave) vehicular communication systems will provide an
abundance of bandwidth for the exchange of raw sensor data and support
driver-assisted and safety-related functionalities. Lack of secure
communication links, however, may lead to abuses and attacks that jeopardize
the efficiency of transportation systems and the physical safety of drivers. In
this paper, we propose two physical layer (PHY) security techniques for
vehicular mmWave communication systems. The first technique uses multiple
antennas with a single RF chain to transmit information symbols to a target
receiver and noise-like signals in non-receiver directions. The second
technique uses multiple antennas with a few RF chains to transmit information
symbols to a target receiver and opportunistically inject artificial noise in
controlled directions, thereby reducing interference in vehicular environments.
Theoretical and numerical results show that the proposed techniques provide
higher secrecy rate when compared to traditional PHY security techniques that
require digital or more complex antenna architectures.
