  C-V2X (Cellular Vehicle-to-Everything) is the important enabling technology
for autonomous driving and intelligent transportation systems. It evolves from
LTE (Long Term Evolution)-V2X to NR (New Radio)-V2X, which will coexist and be
complementary with each other to provide low latency, high reliability, and
high throughput communications for various C-V2X applications. In this article,
a vision of C-V2X is presented. The requirements of the basic road safety and
advanced applications, the architecture, the key technologies, and the
standards of C-V2X are introduced, highlighting the technical evolution path
from LTE-V2X to NR-V2X. Especially, based on the continual and active promotion
of C-V2X research, field testing and development in China, the related works
and progresses are also presented. Lastly, the trends of C-V2X applications
with technical challenges are envisioned.
