What is the right vehicle communication technology for safety?
Onn Haran, founder and CTO of Autotalks and the inventor of the world’s first V2X chipset, looks at the challenges of direct V2X and its cellular equivalent.
Vehicle communication with V2X holds the promise to improve driver safety and comfort. There are two main approaches: Vehicle-to-everything communication (V2X), which uses a dedicated channel to directly exchange information between nearby road users, without involving the cellular network, and network communication, also known as V2N2X, which uses the cellular network to exchange information via multiple clouds. Hybrid communication combines both V2X and network communication.
The major decision factors of these technologies are service availability, business model, privacy, latency and cybersecurity. Misunderstanding can, at best, delay their deployment or, at worst, result in applying the wrong technology for the intended task. Instead of dismissing their differences, clear boundaries must be established so that stakeholders and the industry understand the specific functions of each technology.
The architecture of a V2X network is straightforward: a road user broadcasts a message, and all nearby road users receive it. The network communication architecture is fundamentally different. Road user transmission begins by connecting to the manufacturer’s (OEM’s) cloud via the cellular network, which may use a different mobile operator for each OEM. After processing, the OEM cloud sends the data to a centralized information-sharing cloud, which then distributes the message to the relevant OEMs’ clouds. Finally, the message is sent through the cellular network back to the intended road user.
Figure 1: Architectures of the V2X and V2N2X communication networks
All OEMs have a cloud service but in the case of two-wheelers and aftermarket devices, third-party companies would need to develop and offer safety cloud services.
Vehicular communication serves two primary purposes: enhancing the driver’s situational awareness and warning the driver in safety-critical scenarios. Situational awareness includes information like lane closure or a stopped vehicle on the road shoulder. Safety-related actions warn the driver when they are about to hit another road user of any type: vehicle, bicycle, or pedestrian. The safety-related action roadmap targets using communication to automatically apply vehicle brakes to prevent accidents.
Network communication excels in elevating situational awareness. While the V2X range is up to around 1.5km, network communication can indicate a road closure further along the route. V2X remains effective for most situational awareness warnings, for example, notifying drivers of road works.
When safety-related actions are involved, the only viable communication technology is V2X due to multiple aspects:
Service availability: Safety is needed everywhere and at all times. V2X operates without infrastructure and guarantees full availability. Conversely, network communication relies on cellular coverage. Remote roads and some highways often lack cellular coverage and city centers can experience low network availability. Additionally, 5G network slicing is not yet implemented, so the cellular network does not isolate the safety data from non-safety data.
The FCC (Federal Communications Commission) maintains a map of cellular coverage in the US, revealing very poor coverage in rural areas: 54% for 4G and 18% for 5G. According to NHTSA statistics, rural areas experienced 17,103 traffic fatalities in 2021, accounting for 43% of total fatalities. A safety network that ignores 43% of fatalities is unacceptable.
Figure 2: US roads cellular coverage for urban and rural areas
Network communication has poor coverage on rural roads and cannot guarantee constant availability.
Business model: Safety is a fundamental right for all road users and cannot be denied to those with lower incomes. OEMs are cost-conscious and consider the lifetime costs of a vehicle, not just the initial hardware costs. While V2X requires additional hardware, its overall lifetime cost is significantly lower than that of V2N.
V2X operation is free of charge. There are no communication charges, and processing is done for free on-board. In contrast, cellular network usage incurs a substantial monthly fee, often tens of dollars, that must be paid throughout the vehicle’s lifetime. This fee covers communication costs for uploading hundreds of megabytes, and in some architectures, downloading even larger amounts. Additionally, cloud computing costs for analyzing the risk of each message with every nearby road user contribute to the expense.
Safety should not be restricted to new vehicles whose owners can afford these fees or where OEMs sponsor the cost of connectivity. Given that vehicles are commonly driven for up to 20 years, the lifetime cost of cellular network usage can amount to thousands of dollars.
Excluding older vehicles from the safety network harms the safety of all road users. Older vehicles can pose the same risks on the road as newer ones, so they must be included in the V2X network. They also deserve the same level of protection as those with new cars. Since these road users are unlikely to pay monthly fees, a free alternative must be provided. Expecting vehicle owners to pay for lifelong connectivity is presumptuous and undermines social equality.
Privacy: The EU C-ITS security policy outlines specific privacy requirements for vehicle safety communication based on the General Data Protection Regulation (GDPR). Non-safety communication, such as reporting road works, does not follow this policy since the identity and location of road works are not considered private information. However, for safety data, which continuously transmits the vehicle’s location, personal identity must be concealed to prevent tracking the vehicle’s location to reconstruct an individual’s route.
A crucial requirement is to avoid linking the vehicle’s communication ID with personal identity. V2X solves this by using a random, frequently changing ID, which is not possible with network communication. In cellular networks, each road user has two fixed IDs: one representing the road user’s identity and the other representing the OEM. The linkage to the road user ID, stored in the OEMs’ cloud, violates the EU C-ITS security policy.
Even if the OEM hides the road user’s ID when forwarding to the information-sharing cloud, the OEM ID remains visible. This presents a challenge for OEMs, which are obligated to protect their customers’ privacy. The concern is heightened for police vehicles, having unique OEM ID, making it possible to track the location of all police vehicles through the information-sharing cloud. This linkage of OEM IDs would prevent OEMs from sharing accurate data with the information sharing cloud, leading to the exporting only sparse obfuscated location data to conceal the exact route.
Complete anonymity conflicts with the need for full data availability for safety in a cellular network.
Latency: V2X latency is deterministically bounded by 100mS. Network communication entails complex processing across three clouds (source OEM, information sharing, and destination OEM) in addition to cellular latency, potentially involving multiple operators. Despite the advancements promised by 5G and edge computing, the end-to-end latency is still several seconds.
Future vehicle trajectories can only be estimated a few seconds in advance, as the driver might brake, accelerate, or change lanes. In safety situations, a driver is likely to perform an emergency maneuver, reducing the prediction horizon. During these critical moments, the most up-to-date information is essential. For two-wheelers, their maneuverability shortens this prediction horizon to 1.5 seconds, according to studies. Relying on outdated information results in false alerts at best and missed alerts at worst. Both outcomes are detrimental, undermining the drivers’ trust in the technology.
In network communication, shorter latency multiplies the cost. For instance, a 100ms latency is 10 times more expensive than a 1s latency because both communication and cloud processing costs multiply with the number of messages. However, for V2X, the cost remains zero regardless of the latency.
Network communication latency is higher than the future trajectory prediction horizon, exceeding safety-critical requirement.
Cybersecurity: Wireless communication protection is complicated. Both V2X and network communication are secure. The analysis considers the potential damage from a successful attack and the number of possible attack vectors that could be exploited.
The V2X units are security-hardened, rigorously certified, and use robust cryptographic measures and advanced plausibility checkers. An attacker must be near the attacked vehicle. Thus, the number of attack vectors is small, and the damage is confined to a small geographical area.
Network communication involves multiple cloud servers, creating exponentially more attack vectors than V2X, while plausibility checkers are less capable of detecting attacks. An attack could be launched from anywhere in the world, potentially affecting every connected vehicle.
At present, network communication is strictly separated from the vehicles’ driving functions. It is unlikely that OEMs will agree to break that barrier.
Figure 3: Suitable communication technology per time till collision
In conclusion, network communication (V2N2X) is valuable for enhancing situational awareness, such as alerting drivers to road closures ahead. However, it is unsuitable for safety purposes because it requires hefty lifetime costs and cannot ensure anonymous vehicle identity, continuous service availability particularly in rural areas, deterministic short latency and minimal cybersecurity threats.
Conversely, V2X can reliably indicate road risks while ensuring trust. The global traffic accident crisis calls for adding safety measures. Policymakers should promote the deployment of V2X, OEMs should demonstrate leadership by initiating these deployments, and consumers should request V2X technology in their vehicles.
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