Cognitive Radio Vehicular Ad Hoc Networks: Design, Implementation, and Future Challenges

This chapter addresses the research issues related to the design and implementation of Cognitive Radio Vehicular Ad Hoc Networks (CRVs). CRVs are composed of vehicles equipped with reconfigurable Software Defined Radio (SDR) devices and intelligent Cognitive Radio (CR) functionalities, allowing to reconfigure all the aspects of the radio control, including the operating spectrum frequencies. As a result of the increased capacity provided by the opportunistic spectrum access, CRVs can meet the increasing bandwidth demands of existing applications for VANETs, and contribute to support a new generation of applications based on inter vehicular communication. At the same time, some important issues and system characteristics must be considered in the design and implementation of CRVs, which thus cannot be considered a direct application of common CR principles to the vehicular environment. For instance, the mobility of each vehicle is shown to have a significant negative impact on the spectrum sensing operations, in general. However, this fact could be turned into a performance gain if the mobility is predictable or restricted, like in CRVs, as discussed in this chapter. Cooperation can be seen as a natural way to increase the spectrum awareness of each vehicle in a urban environment. At the same time, it poses new questions on how it must be implemented and coordinated with the local sensing activity. In this chapter, we review the distinctive characteristics of CRVs. We provide a survey of existing solutions for spectrum management proposed in the literature and at the same time we discuss the open research problems which at present constitute an obstacle to the effective deployment of these systems.