By Onn Haran

With the existence of multiple V2X standards derived from both WiFi (DSRC) and cellular (LTE-V2X), keeping track of their progress can be challenging. The latest C-V2X generation, 5G-V2X, aims to harmonize the V2X operation in Europe, while promising new features. But what is the practical value of these new features?

Well, it depends. For instance, a 5G-V2X profile can operate using one of 3 different subcarrier spacing configurations in order to further improve radio performance at radical differential speeds. Similarly, its support for higher modulation constellation (QAM256 versus QAM64) enables two slow-moving nearby road users to exchange a large amount of data in a short time.

One feature that truly stands out and offers significant value is Groupcast. As its name suggests, it facilitates many-to-many connectivity. This can be connection-oriented, involving specific group members, or connectionless, where group members dynamically join and leave based on proximity.

Groupcast is critical for advanced V2X use cases, particularly those involving movement coordination, which are classified as Day 3 scenarios. A common misconception is that movement coordination can only be applied once automated vehicles dominate the roads. However, L2+ human-operated vehicles with advanced driving capabilities can already benefit.

Groupcast enables the first killer app: Lane Change Assist Modern vehicles equipped with Automatic Cruise Control (ACC) can execute lane changes when the driver activates the turn signal. However, these systems often struggle with tight gaps or complex merging scenarios. By leveraging Groupcast, vehicles can negotiate planned lane merges with relevant vehicles in the target lane, ensuring that sufficient space is left or adjustments are made, such as slowing down. This enables safer, more efficient lane changes, enhances traffic flow, and improves driver comfort.

To enhance safety, a visual indicator could be integrated into the sideview mirror, positioned next to the blind spot detection alert. This would notify the driver that their vehicle has coordinated with the vehicle in the adjacent lane and is ready to initiate a lane change without requiring manual intervention. It would also signal to drivers in the target lane that a vehicle is about to merge in front of them.

The European Telecommunications Standards Institute (ETSI) has already conducted a pre-standardization study of Cooperative Merging, proposing an implementation framework. A stable draft is available, and while it may take a few years to develop production-grade interoperable systems, this timeline aligns with the broader 5G-V2X deployment schedule.

The second killer app is enhanced reliability for safety. V2X messages are not acknowledged, which is usually not an issue since nearby vehicles, the intended recipients, are likely to receive the message even if a more distant vehicle transmits at the same time.

In most situations, a vehicle isn’t in immediate danger, so a missed message has negligible impact. However, in high-risk scenarios, such as a vehicle making an emergency stop, running a red light, or a bicycle crossing an intersection, it becomes critical that the at-risk vehicle’s transmissions are reliably received. This ensures nearby drivers can take appropriate actions to safeguard both themselves and the vehicles in proximity.

This protection is facilitated by Groupcast. Group members, identified based on their proximity to the at-risk vehicle or bicycle, signal any reception failures, prompting retransmissions until the message is successfully received. Once the high-risk scenario is resolved, the road user switches back to broadcast communication to avoid overloading the network.

In summary, 5G-V2X brings several important enhancements, but the key new feature is Groupcast. OEMs are keen to enhance Adaptive Cruise Control’s functionality, and Connected Lane Change Assist significantly improves both driver safety and the overall experience. Additionally, it ensures that V2X communication reliability is heightened where it matters most: high-risk scenarios.