V2X is key to truly autonomous vehiclesMohammed Hadded | February 24, 2021
According to the Global Status Report on Road Safety 2018 published by the WHO, the number of road fatalities has reached 1.35 million per year. Unfortunately, traffic accidents are now the leading cause of death for people aged between 5 and 29 years.
The autonomous car promises to improve road safety by reducing the number of serious accidents. Furthermore, it will make it possible to fluidify traffic thanks to inter-vehicle communication, as well as to free the driver from road stress.
Autonomous vehicles, also called automated vehicles, are able to make decisions - braking, passing, parking, turning - for a driver, based on the information they capture from sensor arrays. These sensors rely on several radio communication technologies, some of are already employed in today's low-level automated vehicles. These technologies measure and monitor the world around the vehicle, ensuring a comprehensive assessment of road conditions, traffic, pedestrians and the many unpredictable variables possible in any commute.
By now, all engineers and most consumers are acquainted with lidar, radar and camera technologies that help an autonomous auto visualize its surrounding environment. Increasingly, autonomous autos will need advanced telecommunications to achieve safe and predictable operation. Radio-frequency front ends are looked to facilitate communication between vehicle-to-vehicle sensors. This promises to increase safety by leveraging all the relevant sensors in the environment - not just the vehicle's own.
To operate safely and efficiently, autonomous vehicles will need many types of robust data sources and powerful communications technologies. Actually, several present RF technologies allow autonomous cars to share information such as Cellular V2X (C-V2X) and Dedicated Short Range Communication (DSRC).
The Federal Commission Communications has allocated for connected cars the frequency band at 5.9 GHz with a width of 75 MHz band (5.850 GHz −5.925 GHz). In fact, this band of spectrum resources is composed of seven channels; a control channel (CCH) and six service channels (SCH). The control channel is reserved to transmit either management messages, very high priority messages like those related to road safety. The other six channels are exploited to transmit data from the various services announced on the control channel. This communication is known as DSRC.
DSRC/V2X communications systems allow autonomous vehicles to access safety critical data. Each vehicle can communicate with other vehicles, the road infrastructure, and potentially even pedestrians, thanks to digital connections. Thus, it can have a complete view of its environment and traffic conditions.
The deployment of DSRC/V2X solutions requires interoperability between systems and applications. This involves conducting interoperability tests, field tests and certification tests based on the IEEE 802.11p, 1609.2/3/4 and SAE J2945.1 standards. Interoperability testing and certification solutions are required to ensure the integrity and performance of a DSRC system.
Despite good progress on the development of radar, lidar and camera systems, these sensors are limited by line of sight. These technologies cannot sense what is behind the next bend in the road. C-V2X complements the capabilities of these sensors. It provides a 360° view without direct line of sight. This enables the vehicle to sense road conditions further - even at blind intersections and in bad weather. The vehicle will know if it will get red light long before it arrives at an intersection, or can anticipate detours.
In turn, the C-V2X offers greater predictability and by transmitting location, speed, direction of the vehicle. The environment is informed of the intent of the vehicle, and can withhold pedestrians or changing digital signage based on traffic patterns. Without C-V2X, these sensors can only estimate these parameters. Indeed, it will be the basis for the secure, connected vehicle of the future.
C-V2X enables vehicles to communicate locally (without a cellular network) with each other (V2V), with pedestrians (V2P) and with the road infrastructure (V2I). In addition, this technology enables vehicles to communicate with the cloud via cellular networks (V2N).
C-V2X is standardized in 3GPP Release 14 and defines two additional types of communication which together enable a wide range of application scenarios.
- C-V2X direct communications refers to the direct local communication V2V, V2I and V2P to support active safety and improve knowledge of the current environmental situation by allowing important information (e.g. warnings in the event of dangers on the road) to be exchanged and recognized directly. The transmission takes place in the globally harmonized 5.9 GHz ITS frequency band without relying on mobile network coverage or existing cell phones.
- C-V2X network communications, on the other hand, is the network-based communication V2N to support telematics, networked infotainment and safety-relevant application scenarios. The 4G and emerging 5G network of the established mobile network operators are used here.
In order to gain full advantages of DSRC communication and C-V2X capabilities, several studies recommend a hybrid network architecture that integrates different radio frequency access technologies. This helps vehicle manufacturers cope with the problem that in a global rollout, as some regions prefer the established DSRC standard and others rely on C-V2X. With a hybrid V2X solution, the same hardware and software platform can be used for both communication standards, which reduces costs and complexity.
For the autonomous vehicles of tomorrow, the communication technologies must continuously progress in a way to meet the constantly growing safety requirements and application scenarios. This further development will be driven forward with the path to 5G. The basis is the C-V2X specification 3GPP Release 14. Building on C-V2X, 5G offers even more options for the connected vehicle. The exceptionally high data throughput, low latency and improved reliability of 5G will enable vehicles to share important real-time data, thereby supporting fully autonomous driving.
About the author
Mohamed Hadded earned his Ph.D degree in telecommunication systems from Telecom Sud, in Paris. He continued his research activities as an R&D cybersecurity engineer. His current activities include research projects on cybersecurity for connected vehicles. His research interests include vehicular networks, cybersecurity, UAVs, game theory and machine learning. His published his work has appeared in major journals like IEEE Communications Surveys & Tutorials and in IEEE conferences. He has authored or co-authored more than 30 international publications related to V2X and cybersecurity.