Since the turn of the century, vehicle-to-everything (V2X) technology has usually relied on dedicated short-range communications (DSRC) – a “Wi-Fi-like” protocol running on a reserved bit of spectrum to allow vehicles to talk to each other or to road-side infrastructure. Today, it’s much more likely that automakers and suppliers researching and building V2X solutions are using either cellular V2X (C-V2X) or a hybrid between DSRC and C-V2X. You might be wondering, what is C-V2X and what is responsible for this shift in thinking?
V2X: why aren’t we using it?
It’s important to start with the rationale behind V2X, which is primarily road safety. Vehicles communicating to each other may be able to avoid accidents that their drivers don’t see, enhancing capabilities for them to predict and avoid forward collisions and lane change sideswipes. The National Highway Traffic Safety Administration (NHTSA) in the US estimates that vehicle-to-vehicle (V2V) communications alone would reduce accidents by 13%, saving many lives from V-to-V collisions.
However, V2X technology also provides many other benefits besides preventing vehicle accidents:
- Optimizing traffic flow in heavy traffic situations
- Ensuring vehicles avoid striking pedestrians or bicycles
- Assisting emergency vehicles in clearing the roadway
- Helping control safety in construction zones
- Gaining efficiency in platooning multiple vehicles
With all these benefits, why haven’t we seen it in vehicles on the road yet?
Automakers have little incentive to introduce V2X technologies that only work between their own vehicles, or that increase price to consumers with no immediate gain in safety. Because changes to the technology were happening much faster than regulations could be drafted, most early DSRC proposals became obsolete before they gained sufficient industry traction. Yet, DSRC has since been standardized, and governments around the globe have been working on regulations (albeit slowly) that would make it mandatory within the decade. Automakers like VW and Ford are jumping onboard. As they say – watch this space.
Let’s come back to the question at hand: why are industry innovators shifting from DSRC to C-V2X?
1. One radio
One of the biggest reasons for automakers more interested in embracing C-V2X over DSRC is the radio hardware. Most newer vehicles already include a 3G/LTE/4G cellular radio to offer streaming radio services such as TuneIn, Spotify, or Pandora, download over-the-air (OTA) software updates, refresh navigation maps, reroute using current traffic information, or provide an in-vehicle hotspot. If the existing radio hardware can easily add C-V2X, then it’s practically a no-brainer for the automaker to get on the V2X bandwagon with little extra cost.
As it’s designed, C-V2X leverages many of the same protocols and frequencies of standard cellular data communication. This allows it to be more easily integrated into an existing chipset, and Qualcomm has done just that. As they are the industry de facto cellular chipset provider, adding C-V2X to their chips means the odds of having multiple vehicles from multiple vendors that can speak to each other as well as to a road or city network increases exponentially. On the other hand, using DSRC would be more costly with its additional radio and associated hardware. (Note that modifications to the vehicle’s antenna configuration would be needed regardless of whether the OEM chooses C-V2X or DSRC – something we’ll discuss later.)
2. Newer technology
The fundamentals of DSRC have been debated and refined since 1999, while the IEEE standard, IEEE 802.11p, started work in 2005. That’s many years ago now, and a lot in radio design, protocol development, and electronics have changed since then.
The C-V2X standard is significantly more recent. First released in 2016 and developed by chipset vendors and other companies over the next several years; it piggybacks on the development and availability of LTE and 5G technology. C-V2X supports the same use cases and message payloads as DSRC, and while it takes advantage of lessons learned from earlier V2X trials and research, it’s not backwards compatible with DSRC.
Newer isn’t always better, but C-V2X can send messages twice as far and twice as fast as DSRC, is better at handling message conflict, and less expensive to integrate – all benefits from having a fresh and modern take on the technology. What’s not to love?
One of the communication targets within the V2X acronym is V2P – vehicle to pedestrian. V2P systems being tested today depend on road-side infrastructure (typically pole-mounted cameras) to detect pedestrians at busy intersections and transmit their location to approaching vehicles, which limits the effective deployment of V2P solutions to select trouble zones like busy intersections or school crossings. This is another reason innovators are moving away from DSRC. For V2P support that’s ubiquitous, people would need to carry DSRC transmitters in their pockets – and that’s unlikely to happen anytime soon.
However, most pedestrians today are carrying cell phones. Although not in deployment now, upcoming 5G standards that incorporate C-V2X capabilities makes it much more likely that personal cellphones would allow vehicles to detect and avoid pedestrians and cyclists in the future.
How quickly could a C-V2X enabled vehicle detect a cell-phone carrying person? It’s important to understand that using C-V2X for point-to-point communication doesn’t require a cellular network: it can communicate directly between devices without needing a cell base tower as an intermediary. That direct communication is critical to provide the low latency that crash avoidance situations require. With a device-to-device range of one kilometre or under and message turnaround times of sub-one-millisecond (as part of the C-V2X 5G roadmap), even quickly moving vehicles would have plenty of time to detect and brake before coming close to a pedestrian.
4. Dense traffic
One of the other benefits of V2X is improving the vehicle flow in heavy traffic, by either intelligent coordination of vehicles and traffic signals or synchronizing the start/stop of several vehicles at once. And while DSRC works well in most safety applications, it can struggle when there are a lot of vehicles due to too many simultaneous transmissions. This is far from a reason to avoid DSRC. However, due to a number of technical considerations in the way the C-V2X protocol is designed, it operates better in dense traffic.
5. V2X and autonomous
Some expect V2X will become widespread with the rise of autonomous vehicles as a way to help self-driving vehicles capitalize on their safety promise. But implementing V2X is a massive project that won’t happen all at once, and autonomous vehicles must still function in places where there is no vehicle-to-infrastructure (V2I) system in place. They also must coordinate with nearby vehicles that have no vehicle-to-vehicle (V2V) tech installed.
That said, the performance of autonomous vehicles can be improved wherever those systems are available. V2I systems can give self-driving vehicles additional assistance in places with complex road geometries or congested intersections. And V2V technology can allow several autonomous vehicles to coordinate, letting the trailing vehicles brake for problems sooner than line-of-sight lidar or cameras could allow or taking advantage of platooning to improve battery efficiency.
Are these self-driving enhancements dependent on a particular variant of V2X? Not really, no. However, just like in the infotainment case, it’s far more likely that an autonomous vehicle will require connectivity for software updates at a minimum. If the vehicle already has a cellular connection, there’s a much quicker route to C-V2X than DSRC.
Taking both options
With all these reasons to embrace C-V2X, is there still life in DSRC? In fact, yes! Because DSRC was standardized much earlier, regional trials are much more likely to have used DSRC in their proof-of-concept and initial deployments. That means that vehicles on the road today that encounter V2I-enabled technology – such as signals, on-ramps, and pedestrian detection systems – will almost certainly find DSRC systems outnumbering C-V2X. That probably means that at least until C-V2X enabled infrastructure becomes dominant, vehicles may want to be outfitted with both systems.
Because DSRC and C-V2X both need the 5.9 GHz wireless band, it means a single antenna design should work for both. (This assumes the vehicle also has a standard cellular antenna that C-V2X can share.) The DSRC standard is also being revamped to remove some of the current limitations. There’s still some life in the old dog yet!
At Area X.O we love V2X projects and are well equipped to handle both DRSC and C-V2X with LTE or 5G. If you want to learn more, make sure you attend (either in-person or virtually) the CAV Canada 2021 conference where this and many other connected autonomous vehicle topics will be shared and debated. Is V2X your passion or your latest curiosity? Come to CAV Canada 2021 to share your thoughts and discover more. The date is fast approaching – best to register now!