I. Introduction

The evolution of wireless communications technologies has inspired governments, standardization organizations, academic researchers, and automotive manufacturers, to investigate and deploy the communication capabilities in order to increase transportation safety and efficiency, as well as drivers and passengers comfort. By integrating wireless communications devices into vehicles, vehicular networks enable a variety of applications and services for Intelligent Transportation Systems (ITS) and road users. These applications can be classified according to the number of hops traversed in the vehicular network into: 1) one-hop applications, such as disseminating a warning message about a slippery road to the nearby vehicles; and 2) multi-hop applications, such as Internet access, chatting, and interactive gaming between passengers and fixed points located at the infrastructure, or between passengers located in different areas of the city.