Smart Radios for Smart Vehicles: Cognitive Vehicular Networks

The recent strides made in vehicular networks have enabled a new class of in-car entertainment systems and enhanced the ability of emergency responders using opportunistic spectrum usage enabled by cognitive radio (CR) technology. These CR-enabled vehicles (CRVs) have the ability to use additional spectrum opportunities outside the IEEE 802.11p-specified standard 5.9-GHz band. The aim of this article is to provide a taxonomy of the existing literature on this fast-emerging application area of CRV networks, highlight the key research that has already been undertaken, and point toward the open problems. We explore different architectures [i.e., completely decentralized as well as base station (BS) supported], the sensing schemes suited for highly mobile scenarios with emphasis on cooperation, and spectrum access methods that assure the availability of the required quality of service (QoS). Moreover, we describe the design of a new simulator tool that is able to merge information from real-world street maps with licensed user activity patterns, thereby resulting in a powerful platform for testing and analysis of protocols for CRVs. Finally, the article lists several open research challenges aimed at drawing the attention of the reader toward the important issues that need to be addressed to realize the vision of completely autonomous CRVs.