Cellular Vehicle-to-Everything (C-V2X) Technology

DSRC and C-V2X

Advanced vehicle communication systems are not just a convenient feature for the driver. They can also allow a vehicle to communicate with other devices on or near the road, including other vehicles, which is referred to as V2V, vehicle-to-vehicle communication. Vehicle-to-infrastructure communication is also an emerging use case for vehicle connectivity. This involves vehicles communicating with high-tech road signs or roadside transmitters to exchange information. Because people so often carry connected devices, vehicle-to-pedestrian communication also presents some interesting possibilities that may help avoid collisions or provide other helpful real-time information. Vehicles’ ability to connect to cellular networks also has a lot of potential to provide even more utility than the convenience features it is primarily used for now.

The two main technologies that stand out in the world of vehicle connectivity are dedicated short-range communications (DSRC), and C-V2X, which stands for cellular vehicle-to-everything. C-V2X is the newer of the two and leverages either 4G or 5G technologies.  

DSRC is a WLAN-based technology that was initially conceptualized as a way to provide sideline communications, meaning that it would enable a vehicle to speak to another vehicle, roadside device, or a pedestrian. C-V2X is also meant to provide sideline communication, but it is a cellular technology with the ability to communicate with a cellular base station, a gNodeB or an eNodeB. Integration of the cellular base stations into C-V2X greatly enhances communication with pedestrians whose cell phones are also connected to the same cellular networks. 

The FCC has allocated the 5.9 gigahertz band for both technologies and both tend to operate in similar, smaller-channel bandwidth allocations. The communication range is largely the same, but C-V2X tends to excel in the in the fact that it can leverage the base station coverage to improve latency. Low latency is especially critical to any kind of safety feature that this technology is used for, since a lag in communication could make it ineffective in quick decision-making. 

One of the most critical and interesting potential use cases for C-V2X involves the integration of machine learning, or what is now commonly referred to as AI. Using real-time data from connected vehicles on the road could help predict traffic patterns, monitor the effectiveness of road signs and traffic lights, provide safety recommendations for hazardous driving areas, and generate other data that is useful to drivers, pedestrians, and even city planners or police, both in the short and the long term. 

The Regulatory Environment for Connected Vehicle Technology

The U.S. Department of Transportation reports tens of thousands of vehicle crashes and, tragically, thousands of crash fatalities every year. In addition to the physical harm they can cause, vehicle crashes also cause a staggering amount of property damage and medical expenses every year and require public resources in the form of emergency services, police, and firefighters. The Department of Transportation is very interested in how technology can be deployed to help improve road safety, so they have already been working with other federal regulators, like the FCC, for years to help pave the way for today’s connected vehicles. 

The FCC first allocated the 5.9 GHz spectrum for use by “intelligent transportation systems” in 1999, but at the time this was something of a preemptive decision. Consumer cellular technology was relatively new, but long-distance communication was improving and computing was advancing rapidly, so the FCC realized that radio devices would most likely be integrated into vehicles eventually. 

In 2003, the IEEE published an amendment to the 802.11 standard called 802.11p, which specifically introduced DSRC operation. A few years later, in 2006, the FCC published its first iteration of the technical service rules under Part 90 Subpart M. 

In 2010, with connectivity technology starting to become a normal part of consumers’ lives, the regulatory environment for connected vehicles truly started to mature. The U.S. DOT initiated what they called the Connected Vehicle Safety Pilot Program, whose sole purpose was to demonstrate the readiness of DSRC-based technology for real-world usage in vehicles. The program was largely deemed a success, as it showed that DSRC could operate safely and effectively and had the potential to reduce vehicle crashes. The technology would go on to gain public acceptance because of this program. 

In 2015, the National Highway Traffic Safety Administration announced its intention to mandate that all vehicles use DSRC technology. The following year, the U.S. DOT worked with the FCC to release a Notice of Proposed Rulemaking for vehicle-to-vehicle communications using DSRC based technology. 

In 2017, Release 14 of the Third Generation Partnership Project (3GPP) finalized the first version of C-V2X. In 2019 and 2020, 3GPP would issue Releases 15 and 16, which incorporated new features to C-V2X, essentially improving communication performance to support remote driving, enhancing safety features, reducing latency, and leveraging advancements in 5G technology. 

Starting in 2022, the FCC began to allow use of C-V2X technology in the 5.9 GHz band alongside DSRC. The challenge they were faced with is that the Part 90 rules were initially written to exclusively allow for DSRC technology. In 2023, the FCC released the first of several waivers that allowed certain applicants to develop C-V2X technology and utilize the 5.9 GHz band, subject to updated technical service rules. The FCC continues to release waivers that give former and newly named applicants the ability to develop and approve C-V2X devices, including roadside units and onboard units, which are meant to be installed in a vehicle. 

These waivers set forth limits slightly different from the former DSRC limits for radiated power, occupied bandwidth, and the spurious emissions limit. The FCC also specifically limited the former 5850-5925 MHz span to only 5905-5925 MHz operation for C-V2X. 

The C-V2X waivers have been an iterative process for the FCC as they work to create safe and practical carveouts for this new technology, and to incorporate public comments from industry stakeholders into their rulemaking process. 

Approval of a new C-V2X device is subject to the FCC’s Pre-Approval Guidance (PAG) so they can be certain it's coming from one of the applicants named in the waivers. Following FCC approval, the next step is industry/ecosystem approval through organizations such as the OmniAir Consortium and the 5G Automotive Association (5GAA) whose members include automakers, chipset manufacturers, infrastructure providers, and other key stakeholders.  

Both OmniAir and 5GAA participate in the promotion of C-V2X technology, but they play slightly different roles. OmniAir was established in 2004, and its primary focus is developing certification programs and standards for the testing of C-V2X and DSRC technologies. They help to ensure that connected vehicle technologies are reliable, secure, and interoperable.  

While OmniAir is more focused on the wireless device ecosystem and on testing, The 5G Automotive Association is more focused on promoting the use of 5G technology for CV-V2X applications. 5GAA was established in 2016 and is an advocacy organization that highlights research, advancements, use cases, and other information related to 5G-based technology.

The Future of C-V2X Technology

Through the ongoing waiver process, the FCC is continuously bringing in new applicants and allowing more automakers, chipset manufacturers, and others in the connected vehicle industry to develop C-V2X technology. Because this is still a developing innovation, both the manufacturing and regulatory environments are changing rapidly. For example, in November 2023, the NHTSA announced that it would withdraw its 2015 proposal to require DSRC-based vehicle-to-vehicle communication. With newer C-V2X technologies now available, mandating DSRC would only hinder progress. 

Testing C-V2X devices for FCC approval has largely been based on the waiver, which spells out the requirements for occupied bandwidth and other technical specifications, but these requirements have not yet been codified into federal regulations under a CFR Title 47. With the proliferation of C-V2X technology and in response to widespread interest in C-V2X in the automotive industry, the FCC will inevitably issue updated formal requirements that streamline the current system. 

The connected vehicle experts at Element have been closely following the development of C-V2X technology and have provided testing services for various C-V2X devices. If you have questions about this technology or about Element’s testing capabilities, please reach out via element.com.