C-V2X技术
What is C-V2X?
C-V2X is the V2X communication technology used in China, the US and in the future in Europe. C-V2X is defined by 3GPP standard based on cellular modem technology which uses PC5 interface in the 5.9 Ghz band to transmit and receive messages between vehicles, motorcycles, and Road Side Units (RSU).
Direct Communication
C-V2X technology includes two communication links: Vehicle to Network (V2N), based on the existing cellular network (Uu), and Vehicles to Vehicle (V2V) direct communication not using the cellular network. It is of utmost importance to note, that all V2V safety use-cases require a direct communication link between road users.
Safety-critical V2V messages and cellular V2N infotainment messages have different requirements such as real-time vs. non-real-time, reliability and security targets. In our context, C-V2X refers solely to the direct communication link (PC5).
The separation between the devices handling the network and direct communication links is essential to assure safe and secure vehicle control.
C-V2X Standards
C-V2X was first introduced in 3GPP Release 14 LTE standard in 2017, as an extension of LTE’s Proximity Services (ProSe) used for device to device (D2D) / Ad-hoc direct communication services. The version is called LTE-V2X since the physical layer utilizes the technology (SC-FDMA) and frame structure as in LTE uplink communication.
C-V2X Progress
The next generation, 5G-V2X, was released in 2020 as part of 3GPP Rel. 16. Rel. 17 and 18 extends 5G-V2X capabilities are backward compatible with Rel. 16.
Rel. 16 introduces the concept of groupcast, a reliable group communication, uniquely enabling manoeuvring coordination between vehicles (“Day3” use-case).
LTE-V2X and 5G-V2X cannot share the same channel. Ongoing C-V2X deployments, like those in the US and China, will persist with LTE-V2X, while new deployments, like those in Europe, will exclusively utilize 5G-V2X.
Two Communication Modes
C-V2X specification defines two communication modes:
• Mode 1/3: Network assisted communication. C-V2X communication relies on the cellular network for scheduling and resource management.
• Mode 2/4: Out-of-coverage/SIM-less operation. C-V2X communication is completely autonomous and independent from cellular network.
All C-V2X deployments are solely Mode 2/4.
Autotalks’ C-V2X
Autotalks introduced LTE-V2X into the 2nd generation devices, CRATON2 and SECTON. The devices support 3GPP Rel. 14/15 compliant top-performance PC5 modem, with dual antenna and diversity for both transmission and reception.
Autotalks 3rd generation devices, TEKTON3 and SECTON3, added 5G-V2X capabilities. The devices can operate concurrently 5G-V2X channel and additional LTE-V2X (or DSRC) channel.
Antenna installation for C-V2X
In May 2020, Autotalks tested antenna installation for C-V2X. The field test was documented in a video and the analysis and results can be found in technical report.
