  Motivated by the potentially high downlink traffic demands of commuters in
future autonomous vehicles, we study a network architecture where vehicles use
Vehicle-to-Vehicle (V2V) links to form relay network clusters, which in turn
use Vehicle-to-Infrastructure (V2I) links to connect to one or more Road Side
Units (RSUs). Such cluster-based multihoming offers improved performance, e.g.,
in coverage and per user shared rate, but depends on the penetration of V2V-V2I
capable vehicles and possible blockage, by legacy vehicles, of line of sight
based V2V links, such as those based on millimeter-wave and visible light
technologies. This paper provides a performance analysis of a typical vehicle's
connectivity and throughput on a highway in the free-flow regime, exploring its
dependence on vehicle density, sensitivity to blockages, number of lanes and
heterogeneity across lanes. The results show that, even with moderate vehicle
densities and penetration of V2V-V2I capable vehicles, such architectures can
achieve substantial improvements in connectivity and reduction in per-user rate
variability as compared to V2I based networks. The typical vehicle's
performance is also shown to improve considerably in the multilane highway
setting as compared to a single lane road. This paper also sheds light on how
the network performance is affected when vehicles can control their relative
positions, by characterizing the connectivity-throughput tradeoff faced by the
clusters of vehicles.
