How V2X actually works.
Six pages, in the order an engineer would want them. The radio choice and why it is now effectively settled. The spectrum, band by band, with the real MHz figures. The messages, with their real names and IDs. The layered station architecture that keeps the messages independent of the radio. And the silicon.
In the order an engineer would want them.
C-V2X
PC5 and Uu, 3GPP Releases 14 through 19, LTE-V2X and NR-V2X, resource allocation modes.
DSRC vs C-V2X
The technical comparison, the measured performance delta, and how the standards war ended.
Spectrum
5.9 GHz allocations in the US, EU, China, Korea, Japan and India, with the real MHz figures.
Message sets
SAE J2735 and the ETSI ITS messages, with IDs and rates.
ITS station architecture
ETSI EN 302 665 — access, networking, facilities, applications, and the two vertical entities.
Chipsets and hardware
NXP, Qualcomm, Autotalks, Microchip, Unex, Quectel, and the OBU/RSU platforms.
If you only read two of them.
Read C-V2X first. It is the radio that carries almost all of this, and the distinction between its two interfaces — the direct sidelink and the network path — explains more of the industry's behaviour than any other single fact.
Then read message sets. Interoperability lives at that layer, not at the radio: two devices from two vendors can share a radio and still be mutually useless if they do not agree on the message.
If you are new to the subject, how V2X works is a better starting point than any page in this section. It covers the same ground without a single standard number.