1. Introduction

The advanced technology of connected and automated vehicles (CAVs) enables vehicles to interact with their internal and external environments to improve road safety, transportation efficiency, and the experience of both drivers and passengers. To empower smart vehicular services especially in the future driverless era, the CAV networks are expected to support high-bandwidth content delivery and reliable accessibility of multifarious applications. However, the limited radio spectrum resources, the inflexibility in accommodating dynamic traffic demands, and geographically constrained fixed infrastructure deployment of current terrestrial networks pose great challenges in ensuring ubiquitous, flexible, and reliable network connectivity. To address these challenges in a cost-effective way, heterogeneous vehicular networks (HetVNets) that integrate terrestrial networks with non-terrestrial networks can be leveraged to boost network capacity, enhance system robustness, and provide ubiquitous 3D wireless coverage. Furthermore, mobile edge caching technologies can be utilized in HetVNets to further mitigate backhaul traffic burden and reduce vehicular content delivery delay. In this chapter, we first provide an overview of the vehicular content delivery networks and then elaborate the mobile edge caching-assisted HetVNets with differentiated network characteristics. Finally, we present the key research problems investigated in this monograph.