Vehicle-to-everything (V2X) is a communication method that enables wireless information exchange between vehicles and everything else. This has come to include vehicle-to-infrastructure (V2I), vehicle-to-pedestrian (V2P), vehicle-to-vehicle (V2V) and vehicle-to-network (V2N). Information exchanged includes data about the speed and position of surrounding vehicles and these communications promise to help avoid crashes, ease traffic congestion and improve the environment. Figure 1 shows a representation of the vehicles with the networks for V2V side link (SL) and V2N applications with increasing integrated sensing and communication (ISAC) levels. Table 1 shows more details on the type of network, the objects communicating and the application scenarios.
THE PROBLEM STATEMENT AND THE ORIGINS
The U.S. National Highway Traffic Safety Administration (NHTSA) estimates that safety applications enabled by V2X could eliminate or mitigate the severity of up to 80 percent of non-impaired crashes, including crashes at intersections or while changing lanes. NHTSA estimates that V2X technology can prevent 615,000 vehicle crashes and save 1,366 lives annually. This represents a significant proportion of the 42,939 lives that were lost on U.S. roads in 2021.
By 1999, the U.S. FCC had allocated 75 MHz spectrum in the 5.9 GHz (5.850 to 5.925 GHz) band for V2X. This allocation supported new safety applications. These applications were intended to alert drivers about possible collisions from other vehicles beyond the driver’s sight and the field of view of advanced driver assistance systems (ADAS) sensors.
The Wi-Fi-based dedicated short-range communication (DSRC) standard, also known as ITS-G5/802.11p, WLANp and Wi-Fi-p, was approved in 2010. This has had very few original equipment manufacturer (OEM) vehicle implementations on a limited number of models. The use of cellular technologies has emerged as an alternative to DSRC, with the release of cellular V2X (C-V2X) in the 3GPP Release 14 specification in 2017.
DSRC VERSUS C-V2X
DSRC is a wireless short-range communication technology that uses 802.11p to exchange basic safety messages for collision avoidance. C-V2X is V2X delivered via Uu connectivity or the PC5 interface. Uu is a network communications interface between the user equipment (UE) and an LTE or 5G New Radio (NR) base station. The interface can be used for backhaul and/or long-range communication between the infrastructure and the vehicle. PC5 is a direct-mode communication technology operating in the globally harmonized 5.9 GHz intelligent transportation systems (ITS) band. C-V2X can be deployed as a pure Uu-based system or as a combined solution using PC5.
5G NR-V2X has lower latency, broader bandwidth and better scalability compared to LTE-V2X. From an application point of view, LTE-V2X is mainly designed to support ADAS, improve road safety and improve traffic efficiency. 5G NR-V2X, together with artificial intelligence (AI) and big data are aiming for better support of higher-level autonomous driving, overall traffic management and other new functions. In terms of technical development, 5G NR-V2X, based on the 5G air interface, is an evolutionary improvement of LTE-V2X and the two solutions complement each other.
In the device-to-device PC5 mode (V2V, V2I, V2P) operation, C-V2X does not necessarily require any cellular network infrastructure and can operate without a SIM, without network assistance and uses GNSS as its primary source of time synchronization. By not using cellular network infrastructure for every use case, C-V2X can be a cost-effective safety solution without payment network data usage and V2V and V2I applications built on C-V2X can be launched independently of 5G network rollout. Details of the interfaces in this evolutionary path are shown in Figure 2.
C-V2X has the advantage of offering a clear path from 4G LTE to 5G NR. The initial C-V2X standard included in 3GPP Release 14 focused on V2V communications and fundamental modifications to PC5. The expectation was that further enhancements to support additional V2X operational scenarios would follow.
Further 3GPP releases have addressed a whole host of enhancements. These include a full set of 5G standards, multimedia priority service, V2X application layer services, 5G satellite access, LAN support in 5G, wireless and wireline convergence for 5G, terminal positioning and location, communications in vertical domains, edge computing and network automation, novel radio techniques and increased power efficiency supporting UE devices carried by vulnerable road users (VRUs) including pedestrians and cyclists. Figure 3 shows a timeline for future enhancements.
V2X OPPORTUNITIES AND CHALLENGES
There are many opportunities in the C-V2X industry. These include vehicle safety for passengers and VRUs that include pedestrians and cyclists, safety, mapping, vehicle positioning, autonomous vehicle AI and computing technology. For a single vehicle, C-V2X can help collect perception-related information and send it to the vehicle to improve decision-making and route planning. There are inevitable blind spots or missed detections in the single-vehicle perception of intelligent and connected vehicles. The state information of vehicle perception blind spots such as corners and intersections provided by C-V2X roadside units (RSUs) can effectively expand the vehicle’s perception range. This can improve the safety redundancy and enhance the decision-making ability of autonomous driving.
With the support of a V2N-enabled cloud-controlled platform and C-V2X technology, the goal is to achieve “pedestrian-vehicle-road-cloud” collaborative control at the traffic/transportation level. Achieving this means that C-V2X provides effective information for single-vehicle decision-making in addition to achieving autonomous traffic control of all road sections. This control will extend to all weather and traffic conditions for all traffic participants. A challenge to this goal is the mixed-traffic environment with vehicles of different intelligence levels. Achieving this goal will be beneficial to traffic control and management on a local and national level.
However, there are still doubts about V2X and V2I collaboration and business case realities. Continued wireless spectrum regulatory issues and the lack of government mandates for V2X technology adoption on new vehicles have stalled the widespread adoption of V2X outside of China. Some in the industry see V2X networks as a complementary technology to high-level, large-scale autonomous driving and ADAS implemented in onboard, single-vehicle intelligence. Challenges to V2X implementation include:
High cost of deploying new infrastructure: According to the U.S. DOT, the average cost of C-V2X infrastructure construction at a single intersection is $6,000 to $7,000. This includes the cost of mapping the intersection, purchasing RSUs and installing them in the field.
Onboard hardware costs: OEMs currently bear the costs for the onboard unit (OBU) and they face a difficult situation: V2V applications cannot be triggered because very few cars support V2V. Without seeing a benefit, consumers will be unwilling to pay for C-V2X functions. If the OEMs cannot make a profit they may curtail C2V investment and this will stagnate development.
Additional vehicle hardware cost: According to ITS America, the OBU cost for C-V2X within an existing telematics control unit is $160 to $170 per vehicle.
Unclear data ownership: The development of V2X technology relies on making infrastructure data, like traffic light data, open source. However, most countries and regions have not yet formed clear regulations on the ownership of various types of data. This makes it difficult for all demonstrators to obtain data outside their products and there is no unified evaluation standard for data security and credibility.
Multi-department management:V2X is a cross-industry technology involving the automobile, communications, road management, surveying and mapping industries with each having related management departments. Different authorities may have different rules, resulting in inconsistent management and complex processes, creating duplication, crossover and blind spots.
Cybersecurity: The “ISO/SAE21434 Road Vehicles – Cybersecurity Engineering” document specifies requirements for cybersecurity risk management regarding engineering for the concept, development, production, operation, maintenance and decommissioning of road vehicle electrical and electronic systems, including their components and interfaces.
Business model challenges: There is no clear business model for the commercialization of C-V2X. The PC5 transmission mode is now complimentary, meaning all messages that communicate through PC5 are free of charge. The cost of an OBU, which is an important part of C-V2X, includes development costs, testing and hardware and may include validation and certification costs in the future.
V2X DEPLOYMENT PHASES
According to the CAR 2 CAR Communication Consortium,1 V2X will be deployed in three phases:
Day 1 Phase – Awareness Driving: Vehicles and infrastructure transmit information regarding their status information about tolling stations from RSUs, as well as information describing unexpected events like adverse weather conditions and dangerous situations.
Day 2 Phase – Sensing Driving: The V2X system will be extended to permit vehicles and RSUs to share information about objects detected via onboard sensors such as cameras, LiDAR or radar. This phase also includes functional safety in support of semi-automated driving use cases at receiving vehicles.