5G, the driving force behind the evolution of connected vehicles, brings advantages to V2X applications

Due to the needs of emerging in-vehicle network applications such as vehicle-to-everything (V2X), strict service quality requirements are put forward for latency, data rate, reliability and communication distance. In addition, V2X applications are transitioning to 5G-based, which brings some key features and functionalities missing compared with the current dedicated short-range communication methods. This article will discuss the main advantages of using 5G for V2X applications in autonomous driving systems.

Vehicle-to-everything (V2X) technology is the future of transportation. By communicating with each other on the road (V2V) and with traffic infrastructure such as streetlights and crosswalks (V2I), it will greatly enhance automotive safety features and relieve traffic congestion. V2X can use 5G to transmit signals between cars, pedestrians and traffic cameras/sensors, making driving safer and more convenient.

Next, this article will discuss five ways in which 5G can provide new features in V2X applications, providing better connectivity and lower latency than the current dedicated short-range communication (DSRC) system.


Technology evolution is coming



Figure 1: C-V2X can complement sensors such as cameras, radar and lidar through non-line-of-sight perception, which is a key factor in achieving safe autonomous driving. (source: metamorworks/Shutterstock.com)

V2X and 5G can achieve the goal of enhancing road safety by receiving information about approaching emergency vehicles (including distance and direction information) and school/pedestrian lanes. When children are about to cross the road, school buses can notify nearby vehicles to avoid them, and when a blocked lane appears on a busy street, a delivery truck can let the surrounding area know. Information about traffic congestion will be delivered in real time, and warnings about road accidents or traffic congestion will be transmitted within seconds after they occur. Pedestrians can even receive warnings about nearby vehicles driving abnormally or at unsafe speeds through their mobile phones. When a speeding vehicle runs through a red light and crosses an intersection, pedestrians will hear a loud alarm before stepping onto the road.

Cellular C-V2X (C-V2X) is a subset of V2X that complements sensors such as cameras, radar and lidar by sensing in non-line-of-sight (LoS) ways, which is a key factor in achieving safe autonomous driving. C-V2X will also provide greater coverage than LoS sensors and is the basis for vehicles to communicate with other connected devices.

In addition to V2X, 5G will also support vehicle-to-infrastructure (V2I), vehicle-to-network (V2N), vehicle-to-vehicle (V2V), vehicle-to-pedestrian (V2P) and vulnerable road users such as cyclists, vehicle-to-device (V2D) for electric vehicle power transfer, and vehicle-to-grid (V2G) communications.




Figure 2: Key C-V2X use cases: vehicle-to-vehicle (V2V), vehicle-to-pedestrian (V2P), vehicle-to-infrastructure (V2I) and vehicle-to-network (V2N) communications.

Improve safety with DSRC and C-V2X
Autonomous vehicles use two high-speed communication protocols to ensure vehicle safety: DSRC and C-V2X, which operate at very high speeds and exchange high-frequency data with low latency. DSRC operates in the 5850-5925MHz frequency band with a data rate of 6-26Mbps; C-V2x has a receive rate of 26Mbps (RX) and a maximum transmit rate of 26Mbps (TX). DSRC and C-V2X radios can be unconnected, but they can broadcast vehicle location, speed, acceleration, etc. while listening to other signals.


Safe and reliable communication at all distances
5G brings sidelinking technology to the industry C-V2X by promoting C-V2X-based applications such as vehicle platooning, advanced driving, extended sensors, and remote control driving. Since emergency braking and collision avoidance are required in emergency driving situations, strict low latency and high reliability are required. The shortest transmission delay of C-V2X does not exceed 4ms, and it may be faster, depending on the implementation.

Most of the traffic caused by short-range communications, especially in the first phase of V2X deployment, will be mainly periodic broadcasts of messages by each vehicle to communicate its status and movement.

In densely trafficked areas, available channel resources can saturate the area and increase datagram loss, which can endanger drivers. Certain parameters can be checked and defined through congestion control algorithms to modify these conditions before they reach critical levels. C-V2X sidelink communication is the first wireless system to introduce distance as a dimension at the physical layer, providing a unified communication distance for LoS and non-LoS scenarios.

Security/Privacy of V2X Communications
LTE-based V2X communications use high capacity, large cell coverage, and widely deployed infrastructure to support various types of vehicle-to-vehicle communication services for safety and non-safety applications. Organizations such as 3GPP and Qualcomm have developed roadmaps for 5G-based V2X services.

Security defined in 3GPP mainly includes confidentiality, integrity, authenticity, and anti-replay attack capabilities. New privacy and security challenges, such as group-oriented automatic platoon safe mobility management, reliable cooperative driving, efficient and privacy-preserving vehicle big data sharing and processing, will require further research.

V2X applications rely on continuous, detailed location information, which can lead to privacy issues. In private vehicles, location tracking will show the location changes and activities of the driver (who may or may not be the owner of the vehicle); sending and broadcasting V2X user location information may raise privacy issues for owners and lessees/borrowers.

Other V2X applications include vehicle-to-vehicle communication, augmenting existing methods to help provide left or right turn assistance, emergency braking warnings, and improved situational awareness at intersections. Expanding on the Waze concept, it can control or recommend speed adjustments to resolve traffic congestion and provide real-time updates on GPS maps for lane closures and highway construction activities. V2X is essential to enable over-the-air (OTA) updates of a large number of software-driven systems in cars, including software applications ranging from map updates to bug fixes to security updates.


V2X Message Protection/Security
V2X communications require strong security to protect messages from fraudulent or misleading use that could lead to security and privacy issues. Another security approach is to sign messages using public key certificates to prevent unauthorized parties from interfering with data transmissions and to securely pseudonymize communications.

Public Key Infrastructure (PKI) consists of policies and procedures for the creation, management, use, storage and revocation of digital security certificates. PKI allows for the secure transmission of electronic messages and requires more than just passwords for authentication.


Testing for robust V2X performance
The importance of predicting the performance of V2X communications in various real-world scenarios cannot be overstated. As driver, passenger and pedestrian safety is of paramount importance, testing is required prior to deployment. Lab testing is a critical first stage to prove important assumptions and test unexpected scenarios. As one such test, the 5GAA Automobile Association operates V2X Performance and Functionality Testing in the V2X Functionality and Performance Test Report, where only C-V2X technology is tested in a lab environment for a highly congested scenario, and even in this congested scenario, C-V2X latency is still subject to the 100ms latency limit set for that scenario.

Some of the key points of interest from these tests include:

‧ C-V2X communications in 20MHz CH183 have the same reliability (datagram reception rate vs. distance) as the same BSM-like message transmission in 10MHz CH184.
‧ The impact of high-load C-V2X transmissions in CH183 on DSRC basic safety transmissions in CH172 is negligible at distances up to 1.4km under LoS conditions.
‧ The impact of high-load C-V2X transmissions in CH183 on V2I and I2V transmissions in CH178 is negligible at distances up to 1.4km under LoS conditions
. ‧ The impact of high-load C-V2X transmissions in CH183 on V2I and I2V transmissions in CH180 is negligible at distances up to 1km under LoS conditions.

Ford and Qualcomm also conducted further field testing to support the latest 5G Automotive Association (5GAA) C-V2X deployment exemption application to the U.S. Federal Communications Commission. C-V2X performs well, especially in line-of-sight (LoS) conditions.

C-V2X is considered ready for deployment with commercial chipsets as per the 5GAA plan and is also considered ready for global deployment in vehicles. 5GAA will work with relevant Standard Development Organizations (SDOs) to drive 5G V2X requirements to create a successful V2X ecosystem.


Conclusion
We can see great market potential for V2X, but it is still in its infancy and we may not be able to fully enjoy many benefits of this technology until it matures. Most traffic systems are not V2X compatible yet, but as V2X systems become more common, traffic systems will be able to adjust traffic light timing as needed to relieve traffic congestion, just like how highways use flow control lights (usually with timers) to avoid large congestion.

Car-to-car connectivity technology is likely to make great progress in the next 20 years or so, and many new models will use some form of V2X technology, especially luxury models. Most of the amenities that were once luxury cars (such as leather seats, sunroofs, cruise control) have become commonplace in cars of all price points. V2X connectivity is expected to become a key capability for vehicles with automated driving systems (ADS), which assess potential hazards in the environment and then respond accordingly. The more information ADS has about its surroundings, the better decisions it can make, and 5G will make connectivity from mobile phones to traffic lights to in-car navigation systems the future of transportation.