V2X communication in electric vehicles: streamlined architecture and solutions

Introduction

For automakers, vehicle safety is of paramount concern. Recent innovations such as vehicle-to-everything (V2X) communication are significant developments in automobile safety. V2X is a crucial component of Advanced Driver Assistance Systems (ADAS) that aims to enhance autonomous driving and smart cities via intelligent transportation systems (ITS). It is an Internet of Things (IoT) application that enables vehicles to communicate with the network (V2N), a pedestrian (V2P), infrastructure (V2I) and other vehicles (V2V), fostering an interconnected ecosystem that enhances traffic efficiency. This article explores the architecture of V2X and delves into its components and their interactions for improved roadway safety.

Figure 1: Different types of V2X applications

The architecture of V2X communication in electric vehicles

The principal objective of V2X communication is to establish communication between vehicles and their surroundings by combining hardware and software elements to improve traffic efficiency, road safety, and the overall driving experience.

Onboard unit (OBU)

For electric vehicles (EVs), the OBU functions as an essential car communication hub. It enables wireless connections with other vehicles, roadside units (RSUs), buildings, and even pedestrians. It is equipped with sensors, processors, GPS, and a separate V2X communication module.

The external hardware components of the OBU include:

• A 4G/5G cellular modem that connects the V2N network to the outside world. The modem connects to the OBU through an mPCI adapter.
• A GPS/GNSS receiver that establishes the real-time positioning of the vehicle. It simultaneously allows the OBU to use Network Time Protocol (NTP) to run a GPS-based time service using the GPS-PPS signal.
• A Controller Area Network (CAN) bus to USB adapter connects to the in-vehicle sensors and actuators network. At the same time, the components of the OBU receive a constant power source from the DC/DC converter.
• All of the OBU's components receive a constant power source from the DC/DC converter.

An OBU can be used for diagnostic and emergency data storage, route planning, and navigation. It can be used in electronic toll collection (ETC), support vehicle-to-vehicle (V2V), vehicle-to-infrastructure (V2I), and vehicle-to-roadside (V2R) communication due to its ability to transmit, collect, and store data.

Figure 2: Essential hardware components of the OBU

Roadside unit (RSU)

An RSU (roadside unit) is a transceiver fixed to a road or pedestrian walkway, acting as a bridge between vehicles and transportation infrastructure. The RSU broadcasts and exchanges data to Onboard Units (OBUs) within its communications zone. If necessary, an RSU can also give operating instructions and channel assignments to the onboard Units. An RSU has two essential functions: streamlining traffic and improving safety.

The external hardware components of RSU include:

• Communication unit. (sensors such as LiDAR systems, and cameras,) and global navigation system satellite (GNSS).
• Edge computing node.
• Power supply.
• Chassis.

In vehicle-to-road communication, the location of RSUs has a significant impact on the communication node. Edge computing node (servers with computing and storage capabilities) is responsible for accessing and processing local information and publishing capabilities, and interacting with the communication unit. The use of power determines the power supply standards and the size of the communication units and power supply modules. The edge computing nodes also determine the chassis specifications.

Using triangulation or vehicle re-identification methods, RSUs collect traffic data and transmit it to traffic control devices and the central traffic management center. Intelligent vehicles with V2I communication capabilities can also collect traffic flow data. Other techniques include two-way GPS or satellite navigation systems, inductive loop detection, traffic video cameras, and audio detection. These data fusion-based approaches create an accurate representation of traffic than any single sensing method.

Figure 3: High-level architecture of the RSU and its context (left) and details of the components on the RSU (right)

Figure 4: Hardware configuration of the Road Side Unit

Figure 5: Roadside units (RSU) and mobile edge server distribution and their service ranges

Cellular-vehicle-to-everything (C-V2X) and dedicated short-range communication (DSRC)

V2X communication enables vehicles use both cellular networks (C- V2X) and dedicated short-range communication (DSRC) to safely connect (V2V) with nearby infrastructure (V2I) and with pedestrians (V2P). Cellular networks suit long-distance communication, whereas DSRC is ideal for short-distance, low-latency communication. The specific use case and needs determine the choice of communication strategies.

DSRC and C-V2X are based on separate technologies. However, they employ the same message sets (SAE J2735 and J2945) and communicate directly over the same 5.9 GHz frequency range, resulting in fundamentally different operational approaches. DSRC evolved from WiFi, is optimized for cost and simplicity, and allows dispersed operation by default. C-V2X, which based on LTE, adds new methods to enable distributed processes. For example, a DSRC device using the WAVE wireless protocol, cannot interact with a C-V2X device using Long-Term Evolution (LTE), and vice versa.

Click here and click here to learn more about C-V2X and DSRC and what Element 14 offers. For more details, click here.

Figure 6: V2X services architecture

Figure 7: V2X technology

Let's have a look at the comparative study between C-V2X and DSRC –

C-V2X enhances safety by enabling vehicles to "see" beyond their immediate surroundings. It connects vehicles and roadside infrastructure outside line of sight, facilitating information exchange about traffic conditions. In various applications, C-V2X's supported sensors and services inform drivers, thus preventing crashes and injuries. For instance, using signal phase and timing data, safety applications can assess a vehicle's position and speed to estimate the feasibility of running a red light.

Vehicle-to-vehicle (V2V) communication

V2V communication is based on RF technology. This wireless inter-vehicle communication connects vehicles and enables data to be transmitted over a wireless mesh network for signal exchange. V2V communication, using WiFi or IoT, relies on DSRC for secure, short-to-medium-range, high-speed wireless connectivity. For flawless vehicle communication, two sets of components are crucial: one for accurate and safe transmission of messages and the other for confirming the reception of messages and their consequent interpretation by the receiving vehicle, with messages displayed on the panel.

A few specific wireless technologies for seamless connectivity in autonomous vehicles are:

• Satellite-Based Global Positioning System (GPS)
• Inertial Navigation System (INS)
• Laser Illuminated Detection And Ranging. (LiDAR)

V2V technology is poised to outperform current safety programs, including adaptive cruise control, blind-spot detection, rear parking sonar, and backup cameras in vehicles, as it uses Vehicular Ad hoc Networks (VANETs). Vehicles can use these wireless networks to communicate and share information about their driving habits spanning up to 1000 m with a 360° view of their surroundings.

By exchanging real-time data on speed, acceleration, distance, and direction, V2V informs drivers instantly about lane changes, approaching vehicle trajectories, and relative speeds. The driver also receives a large amount of data, including speed, geolocation, braking, stability, and travel direction, playing a crucial role in enhancing road safety by preemptively notifying drivers of incidents.

Figure 8: Configuring velocity in V2V

Figure 9: Vehicles communicating via V2X on highways

Figure 10: Anatomy of a V2V system

Vehicle-to-infrastructure (V2I) communication

V2I uses various supporting devices for two-way wireless information sharing between vehicles and roadside system infrastructure. These devices, like RFID readers, signage, cameras, and streetlights, form a wireless, bidirectional network that effortlessly exchanges information between infrastructure and vehicles. The V2I, like V2V technology, also uses DSRC frequencies(5.9GHz) for data transmission.

Sensors in V2I communication play a crucial part in Intelligent Transportation Systems (ITS), providing real-time advisories on road incidents (traffic, construction, parking, etc.) and aiding traffic management by adjusting speed limits and modifying signal phase and timing (SPaT) for better fuel economy and traffic flow. This technology is helpful for safety and information exchange, including warnings about collisions, traffic, weather conditions, and road issues.

Figure 11: V2I architecture

Figure 12: Example of V2I systems architecture (Source: ITS Joint Program Office, USDOT)

Vehicle-to-pedestrian (V2P) communication

In V2P communication, vehicles directly interact with pedestrians or nearby cyclists and bikers. It involves direct real-time communication between vehicles and vulnerable road users (VRUs), such as pedestrians, cyclists, baby strollers, passengers boarding and alighting public transport, and individuals who utilize wheelchairs with reduced mobility. V2P algorithms operate in three phases—detection, tracking, and trajectory prediction—identifying pedestrians, estimating time-to-collision (TTC), and activating warnings or braking to prevent crashes. This technology enhances safety by exchanging information, with reliability depending on GPS data that warns pedestrians of approaching vehicles and alerts motorists of VRUs.

Both unidirectional and bi-directional communications can be established in V2P.

In the unidirectional method, pedestrian warning systems (accessible via mobile apps) use wearable tech, cameras, or infrastructure to alert pedestrians of oncoming vehicles through auditory, visual, or vibratory alerts. These systems may face limitations for pedestrians without smartphones or in noisy environments.

Bilateral collision alert systems notify drivers and pedestrians simultaneously through point-to-multipoint communication, creating a local wireless network. These systems use DSRC, WiFi, and GPS to operate independently of light, environmental conditions, road state, or vehicle speed. They detect unseen obstacles and alert all parties, providing a significant safety advantage. Efficient bilateral functionality relies on widespread adoption among pedestrians and drivers, with improvements in data communication and compression crucial for reducing latency in V2P alerts.

Figure 13: Vehicle and pedestrian on-road practical situation

Figure 14: Example of V2P for a vehicle approaching a pedestrian

Figure 15: Factors involving pedestrian and pedestrian-to-vehicle communication

Figure 16: Overall cooperative protection system description

Solutions and benefits of V2X communication in electric vehicles

The main benefits of V2X communication in EVs are

V2X enables vehicles to communicate with each other and the infrastructure around them, providing real-time information about other vehicles and potential hazards.

V2X technology can reduce accidents by alarming hazardous road situations (such as congestions, rear-end crashes, curve speed alerts, road weather, obstacles, etc.), helping drivers avoid accidents and lower fatalities and injuries. For example, a red-light violation warning (RLVW) can help drivers avoid accidents and reduce fatalities and injuries on the road. IMA safety applications, such as RLVWs, alert drivers about red-light violations, allowing timely intervention before their vehicle reaches the intersection.

In addition, RSUs at intersections facilitate emergency vehicle preemption (EVP), an everyday use case in major cities worldwide. OBUs in ambulances and fire trucks communicate with RSUs, triggering traffic signal changes in their favor—especially vital in congested city streets prone to gridlocks.

Figure 17: illustrates vehicle-to-everything communication with all road entities connected via V2V, V2I, and V2P communication

V2X reduces congestion, improves traffic flow, and increases road network efficiency, allowing better route planning with lower fuel usage. It also lowers greenhouse gas emissions.

For example, RSUs in congested areas, like junctions and highway merges, enable V2X traffic coordination (e.g., SPaT and lane merge assistance), leading to substantial congestion reduction, lower fuel consumption, and minimal productivity loss.

The innovative parking application of V2X communicates with OBUs in neighboring vehicles via RSUs in parking lots, providing actual information on parking spot availability and eliminating the need to search for parking in metropolitan locations.

Figure 18: Applications of intelligent RSUs in cities

V2X increases the acceptability of autonomous cars for safer and more efficient transportation. It shares data with other vehicles and infrastructure, enabling informed decisions.Transportation agencies can use V2X for better road network management and respond swiftly to accidents.

V2X enhances micro-mobility safety by addressing the common cause of accidents due to "failure to see.” It can communicate with electric scooters, bicycles, and other personal transportation devices and warns drivers about the presence of vulnerable road users. V2X can overcome—visibility challenges posed by other vehicles or infrastructure.

EVs can communicate with infrastructure components such as charging stations thanks to V2X connectivity. An electric car may request information about nearby charging stations, verify availability, and book a slot, enhancing the convenience of electric vehicle ownership.

Conclusion

V2X communication has revolutionized the world of EVs, offering solutions for enhanced safety, traffic management, and overall efficiency. Its intricate architecture, involving OBUs, RSUs, cellular, DSRC, and cloud-based infrastructure, create a seamless network of communication between EVs and their surroundings. The benefits of V2X communication are limitless, from preventing accidents and managing traffic to promoting environmentally friendly driving practices. As the automotive industry continues to embrace this technology, the future of EVs and transportation is set to become more innovative, safer, and more sustainable. V2X communication will undoubtedly play a pivotal role in the ongoing evolution of EVs and the broader transportation ecosystem.