  Recent advances in Vehicle-to-Everything (V2X) technology and the upcoming
sixth-generation (6G) network will dawn a new era for vehicular services with
enhanced communication capabilities. Connected and Autonomous Vehicles (CAVs)
are expected to deliver a new transportation experience, increasing the safety
and efficiency of road networks. The use of millimeter-wave (mmW) frequencies
guarantees a huge amount of bandwidth (> 1GHz) and a high data rate (>
10Gbit/s), which are required for CAVs applications. However, high frequency is
impaired by severe path loss, and line of sight (LoS) propagation can be easily
blocked by static and dynamic obstacles. Several solutions are being
investigated, and the most promising one exploits relays. However, traditional
relay schemes react to link failure and leverage instantaneous information,
which impedes efficient relay selection in highly mobile and complex networks,
such as vehicular scenarios. In this context, we propose a novel proactive
relaying strategy that exploits the cooperation between CAVs and environment
information to predict the dynamic LoS-map, which describes the links'
evolution in time. The proactive relaying schemes exploit the dynamic LoS-map
to maximize the network connectivity. A novel framework integrating realistic
mobility patterns and geometric channel propagation models is proposed to
analyze the performance in different scenarios. Numerical simulations suggest
that the proactive relaying schemes mitigate beam blockage and maximize the
average probability of connecting CAVs with reliable links.
