  Capacity of vehicular networks with infrastructure support is both an
interesting and challenging problem as the capacity is determined by the
inter-play of multiple factors including vehicle-to-infrastructure (V2I)
communications, vehicle-to-vehicle (V2V) communications, density and mobility
of vehicles, and cooperation among vehicles and infrastructure. In this paper,
we consider a typical delay-tolerant application scenario with a subset of
vehicles, termed Vehicles of Interest (VoIs), having download requests. Each
VoI downloads a distinct large-size file from the Internet and other vehicles
without download requests assist the delivery of the files to the VoIs. A
cooperative communication strategy is proposed that explores the combined use
of V2I communications, V2V communications, mobility of vehicles and cooperation
among vehicles and infrastructure to improve the capacity of vehicular
networks. An analytical framework is developed to model the data dissemination
process using this strategy, and a closed form expression of the achievable
capacity is obtained, which reveals the relationship between the capacity and
its major performance-impacting parameters such as inter-infrastructure
distance, radio ranges of infrastructure and vehicles, sensing range of
vehicles, transmission rates of V2I and V2V communications, vehicular density
and proportion of VoIs. Numerical result shows that the proposed cooperative
communication strategy significantly boosts the capacity of vehicular networks,
especially when the proportion of VoIs is low. Our results provide guidance on
the optimum deployment of vehicular network infrastructure and the design of
cooperative communication strategy to maximize the capacity.
