V ehicular networks have attracted a lot of interest in the past decade from both industry and academia. Via enabling vehicles to communicate with each other (i.e., vehicle-to-vehicle, V2V), and with infrastructure (i.e., vehicle-to-infrastructure, V2I), vehicular networks can support enormous applications, which are mainly divided into two categories: safety applications and non-safety applications. Dedicated short-range communication (DSRC) based on IEEE 802.11p has gained increasing attention for its easy deployment, low cost, and capacity to naturally support V2V communications [1]. Nonetheless, it suffers from scalability issues, for example, unbounded delay, limited radio range, and lack of a pervasive roadside communication infrastructure [2] . Thus, the fourth generation (4G) Long Term Evolution (LTE) system is proposed to support vehicular communication [3] . For the vehicle user, it can benefit from the wide coverage, high throughput, and low latency of LTE networks. However, due to high vehicle mobility and dynamic network topology, it is quite difficult to provide satisfactory intelligent transportation system (ITS) services only through LTE. Specifically, when the number of vehicle users increases in the cell coverage, the strict latency requirement of safety applications cannot be guaranteed by LTE itself. Heterogeneous vehicular networks (HetVNETs), by integrating different access networks including DSRC and LTE, are expected to be a viable solution to meet various communication requirements for ITS services [4] . HetVNETs are in the process of constituting a fundamental information platform, and will eventually evolve into all vehicles being connected. However, there are problems that hinder the rapid development of HetVNETs. ITS services proliferate significantly, and different kinds of them can be well supported by different wireless access technologies. Various heteroge- HetVNETs can meet various QoS requirements for intelligent transport system services by integrating different access networks coherently. However, the current network architecture for HetVNET cannot efficiently deal with the increasing demands of a rapidly changing network landscape. Thanks to the centralization and flexibility of the Cloud-RAN, soft-defined networking can conveniently be applied to support the dynamic nature of future HetVNET functions and various applications while reducing the operating costs. In this article, we first propose the multi-layer Cloud-RAN architecture for implementing the new network, where the multi-domain resources can be exploited as needed for vehicle users. Then the high-level design of a soft-defined HetVNET is presented in detail. Finally, we briefly discuss key challenges and solutions for this new network, corroborating its feasibility in the emerging fifth-generation era.
The multi-layer Cloud-RAN architecture REF is proposed for implementing the new vehicular network, where the multi-domain resources can be exploited as needed for vehicle users.
Soft-defined heterogeneous vehicular network: architecture and challenges
IEEE Network
IEEE Network
Computer Science