A Tutorial on Future Vehicular Communications: From Performance Metrics to Open Research Directions

The study of vehicular networks has evolved into a new era thanks to rapid advances in electric, transportation, communication, and automobile technologies. However, the realization of modern applications like autonomous driving, intelligent transportation systems, and the smart city remain a major challenge due to the high requirements for performance metrics like data rate, latency, reliability, connectivity, coverage, and security. Moreover, in vehicular network, the performance metrics are not independent and may have a complex coupling relationship, i.e., optimizing one may result in degrading others. In this paper, we begin with discussing the coupling effect among the aforementioned performance metrics, aiming to provide a basic concept of the challenges of future vehicular networks. We aim to provide a comprehensive review of recent developments in vehicular communication technologies, such as the fifth-generation new radio (5G NR), dedicated short-range communications (DSRC), millimeter wave/terahertz communications, mobile edge computing (MEC), integrated sensing and communication (ISAC), uncrewed aerial vehicle (UAV) assisted vehicular networks, and blockchain-assisted security. The paper also covers the role of AI and its impact on the performance of each of the aforementioned applications. We then summarize several promising areas that can influence the future research in vehicular networks. Lastly, the paper concludes by highlighting key research challenges and future directions in the domain of vehicular networks.