Autonomous vehicles and Intelligent Transport Systems (ITS) have started to become
a reality in recent years. However, shortcomings of these early intelligent vehicles
demonstrate a need to increase an intelligent vehicle's perceptual bubble beyond the
vehicle's onboard sensors. Vehicle-to-Everything (V2X) communications is a technology
intended to enable intelligent vehicles to increase their perceptive range via communication
with the outside world, i.e., other vehicles, road users, and infrastructure. One
of the critical layers of V2X communications is that of the underlying wireless access.
There remains an open debate on which technology (or technologies) will ultimately
be adopted as the de facto wireless access technology for V2X communications. Presently,
a myriad of unconnected threads of work are being undertaken to this end, resulting
in an unclear picture of the current state of wireless access for V2X communications.
In this tutorial review, we collate current research on wireless access for V2X communications
to showcase recent developments and the challenges facing candidate technologies.
To allow the reader to engage with the debate, we present an overview of the field
of V2X communications, its history, and standardisation. Following this, we provide
an overview of the key candidate wireless access technologies that may enable V2X
communications. Through this work, we aim to provide a comprehensive first step into
the discipline of wireless access for V2X communications.
