Vehicle-to-everything (V2X) describes wireless communication between a vehicle and any entity that may affect, or may be affected by, the vehicle. Sometimes called C-V2X, it is a vehicular communication system that is intended to improve road safety and traffic efficiency while reducing pollution and saving energy.
The automotive and communications industries, along with the U.S. government, European Union and South Korea are actively promoting V2X and C-V2X as potentially life-saving, pollution-reducing technologies. The U.S. Department of Transport has said V2X technologies offer significant transportation safety and mobility benefits. The U.S. NHTSA estimates a minimum of 13% reduction in traffic accidents if a V2V system were implemented, resulting in 439,000 fewer crashes per year. V2X technology is already being used in Europe and China.
There are two standards for dedicated V2X communications depending on the underlying wireless technology being used: (1) WLAN-based, and (2) cellular-based. V2X also incorporates various more specific types of communication including: Vehicle-to-device (V2D) - Bluetooth / WiFi-Direct, e.g. Apple's CarPlay and Google's Android Auto. Vehicle-to-grid (V2G) - information exchange with the smart grid to balance loads more efficiently. Vehicle-to-building (V2B), also known as vehicle-to-home (V2H) Vehicle-to-load (V2L) Vehicle-to-network (V2N) - communication between a vehicle and a wider network, such as a cellular network. This category includes telematics, where a vehicle communicates with a fleet management platform or a cloud server. Vehicle-to-cloud (V2C) - e.g. OTA updates, remote vehicle diagnostics (DoIP). Vehicle-to-infrastructure (V2I) - e.g. traffic lights, lane markers and parking meters. Vehicle-to-pedestrian (V2P) - e.g. wheelchairs and bicycles, commonly also used to designate vulnerable road users (VRUs). Vehicle-to-vehicle (V2V) - real-time data exchange with nearby vehicles. History The history of working on vehicle-to-vehicle communication projects to increase safety, reduce accidents and driver assistance can be traced back to the 1970s with projects such as the US Electronic Road Guidance System (ERGS) and Japan's CACS. Most milestones in the history of vehicle networks originate from the United States, Europe, and Japan.
Standardization of WLAN-based V2X supersedes that of cellular-based V2X systems. IEEE first published the specification of WLAN-based V2X (IEEE 802.11p) in 2010. It supports direct communication between vehicles (V2V) and between vehicles and infrastructure (V2I). This technology is referred to as dedicated short-range communication (DSRC). DSRC uses the underlying radio communication provided by 802.11p.
In 2016, Toyota became the first automaker globally to introduce automobiles equipped with V2X. These vehicles use DSRC technology and are only for sale in Japan. In 2017, GM became the second automaker to introduce V2X. GM sells a Cadillac model in the United States that also is equipped with DSRC V2X.
In 2016, 3GPP published V2X specifications based on LTE as the underlying technology. It is generally referred to as "cellular V2X" (C-V2X) to differentiate itself from the 802.11p based V2X technology. In addition to the direct communication (V2V, V2I), C-V2X also supports wide area communication over a cellular network (V2N).
As of December 2017, a European automotive manufacturer has announced to deploy V2X technology based on 802.11p from 2019.An assessment of LTE-V2X (PC5) and 802.11p direct communications technologies for improved road safety in the EU.(http://5gaa.org/wp-content/uploads/2017/12/5GAA-Road-safety-FINAL2017-12-05.pdf) While some studies and analysis in 2017 and 2018,White Paper on ITS spectrum utilization in the Asia Pacific Region (http://5gaa.org/wp-content/uploads/2018/07/5GAA_WhitePaper_ITS-spectrum-utilization-in-the-Asia-Pacific-Region_FINAL_160718docx.pdf) all performed by the 5G Automotive Association (5GAA) – the industry organisation supporting and developing the C-V2X technology – indicate that cellular-based C-V2X technology in direct communication mode is superior to 802.11p in multiple aspects, such as performance, communication range, and reliability, many of these claims are disputed, e.g. in a whitepaper published by NXP,C-ITS: Three observations on LTE-V2X and ETSI ITS-G5—A comparison (https://www.nxp.com/docs/en/white-paper/CITSCOMPWP.pdf) one of the companies active in the 802.11p based V2X technology, but also published by peer-reviewed journals.
This technology can be misused to remotely control the vehicle. The Police of the Czech Republic in cooperation with universities has developed a system for remote stopping of vehicles with reference to the fact that such a procedure is legal even under the current legislation.
Technology overview
802.11p (DSRC)
The original V2X communication uses WLAN technology and works directly between vehicles (V2V) as well as vehicles and traffic infrastructure (V2I), which form a vehicular ad-hoc network as two V2X senders come within each other's range. Hence it does not require any communication infrastructure for vehicles to communicate, which is key to ensure safety in remote or little-developed areas.
WLAN is particularly well-suited for V2X communication, due to its low latency. It transmits messages known as Cooperative Awareness Messages (CAM) or Basic Safety Message (BSM), and Decentralised Environmental Notification Messages (DENM).
Other roadside infrastructure related messages are Signal Phase and Timing Message (SPaT), In Vehicle Information Message (IVI), and Service Request Message (SRM). The data volume of these messages is very low. The radio technology is part of the WLAN IEEE 802.11 family of standards and known in the US as Wireless Access in Vehicular Environments (WAVE) and in Europe as ITS-G5.EN 302 663 Intelligent Transport Systems (ITS); Access layer specification for Intelligent Transport Systems operating in the 5 GHz frequency band (http://www.etsi.org/deliver/etsi_en/302600_302699/302663/01.02.00_20/en_302663v010200a.pdf) To complement the direct communication mode, vehicles can be equipped with traditional cellular communication technologies, supporting V2N based services. This extension with V2N was achieved in Europe under the C-ITS platform umbrella with cellular systems and broadcast systems (TMC/DAB+).
3GPP (C-V2X)
V2X communication over cellular networks is called cellular V2X (or C-V2X) to distinguish it from WLAN-based V2X. There have been multiple industry organizations, such as the 5G Automotive Association (5GAA), promoting C-V2X due to its advantages over WLAN-based V2X (without considering disadvantages at the same time).The Case for Cellular V2X for Safety and Cooperative Driving (http://5gaa.org/wp-content/uploads/2017/10/5GAA-whitepaper-23-Nov-2016.pdf) C-V2X is initially defined as LTE in 3GPP Release 14 and is designed to operate in several modes: Device-to-device (V2V or V2I), and Device-to-network (V2N).
In 3GPP Release 15, the V2X functionalities are expanded to support 5G. C-V2X supports both direct communication between vehicles (V2V) and traditional cellular network-based communication. Also, C-V2X provides a migration path to 5G based systems and services, which implies incompatibility and higher costs compared to 4G based solutions.
Direct communication between the vehicle and other devices (V2V, V2I) uses the PC5 interface. PC5 refers to a reference point at which the User Equipment (UE), i.e., a mobile handset, directly communicates with another UE over a direct channel. In this case, the communication with the base station is not required. At the system architectural level, proximity service (ProSe) is the feature that defines the architecture for direct communication between UEs. In 3GPP RAN specifications, "sidelink" is the term used to refer to direct communication over PC5. PC5 interface was originally defined to address the needs of mission-critical communication for the public safety community (Public Safety-LTE, or PS-LTE) in release 13. The motivation for mission-critical communication was to enable law enforcement agencies or emergency rescue teams to use LTE even when infrastructure is unavailable, such as during a natural disaster. From release 14 onwards, the use of the PC5 interface has been expanded to meet various market needs, including communication with wearable devices, such as smartwatch. In C-V2X, the PC5 interface is re-applied to the direct communication in V2V and V2I.
The Cellular V2X mode 4 communication relies on a distributed resource allocation scheme, namely sensing-based semipersistent scheduling which schedules radio resources in a stand-alone fashion in each user equipment (UE).
In addition to the direct communication over PC5, C-V2X also allows the C-V2X device to use the cellular network connection in the traditional manner over the Uu interface. Uu refers to the logical interface between the UE and the base station. This is generally referred to as vehicle-to-network (V2N), the mechanism that enables conventional telematics services. V2N is a unique use case for C-V2X and does not exist in 802.11p-based V2X, since the latter supports only direct communication. However, as with WLAN-based V2X, in C-V2X, two communication radios are required to communicate simultaneously via a PC5 interface with nearby stations and via the UU interface with the network.
While 3GPP defines the data transport features that enable V2X, it does not include V2X semantic content; instead, it proposes using ITS-G5 standards such as CAM, DENM, and BSM over 3GPP V2X data transport features.3GPP Release 15 (https://www.3gpp.org/release-15)
Use cases
Through its instant communication, V2X enables road safety applications such as (non-exhaustive list):
Forward collision warning Lane change warning/blind spot warning Emergency electric brake light warning Optimal speed advisory (through traffic lights) Emergency vehicle approaching Roadworks warning Platooning Fleet management: Utilizing V2N communication for telematics applications such as remote vehicle diagnostics, fleet management software, track and trace of assets, and communication with a central dispatch platform. Energy efficient intersection control Prevention of red light running
In June 2024 the U.S. Department of Transportation announced that it is awarding $60 million in grants to advance connected and interoperable vehicle technologies under a program called "Saving Lives with Connectivity: Accelerating V2X Deployment program". It said the grants to recipients in Arizona, Texas and Utah would serve as national models to accelerate and spur new deployments of V2X technologies. European standardisation body ETSI and SAE published standards on what they see as use cases.ETSI TR 102638: Intelligent Transport Systems (ITS); Vehicular Communications; Basic Set of Applications; Definitions (http://www.etsi.org/deliver/etsi_tr%5C102600_102699%5C102638%5C01.01.01_60%5Ctr_102638v010101p.pdf)SAE J2945/x family of standards: (http://standards.sae.org/wip/j2945/ ) Early use cases focus on road safety and efficiency. Organizations such as 3GPP and 5GAA continuously introduce and test new cases. The 5GAA has published several roadmaps which highlight the technical potential and challenges of new use cases. Some use cases address high levels of automation.
C-V2X offers further use cases including slippery road, roadworks and road hazard information to cars and trucks over hills, around curves and over longer distances than is possible with direct communications. Volvo, for example, has sold new cars that warn other Volvos of slippery roads ahead using C-V2X communications since 2016 in Denmark, and has announced plans to complement that with general accident-ahead warnings and offer the same functionality in other European markets over time.