  Millimeter-wave (mmwave) communication represents a potential solution to
capacity shortage in vehicular networks. However, effective beam alignment
between senders and receivers requires accurate knowledge of the vehicles'
position for fast beam steering, which is often impractical to obtain in real
time. We address this problem by leveraging the traffic signals regulating
vehicular mobility: as an example, we may coordinate beams with red traffic
lights, as they correspond to higher vehicle densities and lower speeds. To
evaluate our intuition, we propose a tractable, yet accurate, mmwave
communication model accounting for both the distance and the heading of
vehicles being served. Using such a model, we optimize the beam design and
define a low-complexity, heuristic strategy. For increased realism, we consider
as reference scenario a large-scale, real-world mobility trace of vehicles in
Luxembourg. The results show that our approach closely matches the optimum and
always outperforms static beam design based on road topology alone. Remarkably,
it also yields better performance than solutions based on real-time mobility
information.
