  The next generations of vehicles will require data transmission rates in the
order of terabytes per driving hour, to support advanced automotive services.
This unprecedented amount of data to be exchanged goes beyond the capabilities
of existing communication technologies for vehicular communication and calls
for new solutions. A possible answer to this growing demand for ultra-high
transmission speeds can be found in the millimeter-wave (mmWave) bands which,
however, are subject to high signal attenuation and challenging propagation
characteristics. In particular, mmWave links are typically directional, to
benefit from the resulting beamforming gain, and require precise alignment of
the transmitter and the receiver beams, an operation which may increase the
latency of the communication and lead to deafness due to beam misalignment. In
this paper, we propose a stochastic model for characterizing the beam coverage
and connectivity probability in mmWave automotive networks. The purpose is to
exemplify some of the complex and interesting tradeoffs that have to be
considered when designing solutions for vehicular scenarios based on mmWave
links. The results show that the performance of the automotive nodes in highly
mobile mmWave systems strictly depends on the specific environment in which the
vehicles are deployed, and must account for several automotive-specific
features such as the nodes speed, the beam alignment periodicity, the base
stations density and the antenna geometry.
