Navigating the Future of V2X

Imagine a society where movement is fully connected and automated, enabling safe transportation across all modes that prioritize mobility, equity, and sustainability. A society that has moved beyond a transportation system plagued by traffic congestion, transportation deserts, and fossil-fueled vehicles. A 21st century society enabled by Intelligent Transportation Systems (ITS) that has overcome the physical limitations, inequitable legacies, and unsustainable development patterns of 20th century infrastructure.

The central focus of this ITS vision is a transportation network comprised of connected and automated vehicles (CAV) – where vehicles and traffic systems communicate using vehicle-to-everything (V2X) technology to support safer travel. This technology orchestrates the seamless movement of on-road vehicles to enable an ‘intelligent’ system that can save lives, reduce congestion, and promote more sustainable modes of travel. While the technology has proven benefits demonstrated over decades of testing, infrastructure owners and operators (IOOs) must navigate regulatory and market forces to shift from the pilot demonstrations today to the widescale deployment of ITS envisioned for the future.

Industry Overview: The Current Landscape for ITS

CAV has been a focus of USDOT-funded ITS research for nearly two decades and comprises of safety applications using V2X technology. Connectivity is a critical enabler of V2X: historically, there’s been 75 MHz of spectrum within the 5.9 GHZ Safety Band[1] allocated for transportation and vehicular safety-related communications. Since the allocation of this spectrum in 1999[2], the majority of ITS applications for V2X research and operations of first responder vehicles (ambulances, police, firefighters) have used Dedicated Short-Range Communications (DSRC) technology in the full 75 MHz spectrum.

The recent FCC ruling to repurpose the lower 45 MHz of the Safety Band[3] reduces the available spectrum for ITS to only the upper 30 MHz of the band and mandates a preference for cellular-vehicle-to-everything (C-V2X) – an alternative V2X communications protocol which is not interoperable with DSRC. Proponents of DSRC have argued that the technology outperforms C-V2X on critical safety applications that require minimal latency. Advocates for C-V2X indicate the technology can still deliver intended safety outcomes while also supporting advanced applications such as sidelinking to enable automated vehicle (AV) deployments. Both sides agree that the full 75 MHz is critical for ensuring the effectiveness of ITS safety applications such as vehicle-to-vehicle (V2V) and vehicle-to-pedestrian (V2P) collision avoidance.[4]

Lessons Learned: From DSRC to C-V2X

As debate continues on the spectrum and communication protocol required for V2X applications to safely function, there are lessons we can learn from nearly 20 years of research in DSRC to prepare IOOs for a potential future that may be trending towards a C-V2X dominant, reduced spectrum environment.

Lesson 1: Pilot demonstrations are needed to achieve technology readiness – Testing in real-world settings have helped DSRC mature in technology readiness and for several of its V2X applications to be considered deployment ready today for improving transportation safety. During the early days of DSRC testing, pilot demonstrations such as the Ann Arbor Safety Pilot Model Deployment (AASPMD) experienced many challenges as the project team learned how to architect a large-scale connected vehicle deployment. Despite the challenges, the AASPMD team’s experience helped develop a common set of testing procedures, tools, and templates that are still used by the industry today. Similarly, C-V2X research will benefit from pilot deployments to better understand the transferability of applications between DSRC and C-V2X, as well as the efficacy of ITS application performance on C-V2X in a 30 MHz spectrum environment to enable technology readiness for future deployment.

Lesson 2: Changes to standards will focus on the radio layer, not applications – While the V2X application layer standards are transferrable from DSRC to C-V2X[5], the C-V2X radio layer standards are still in the process of being translated from 3GPP to SAE through various working groups. This translation effort underpins the interoperability and data integrity for C-V2X, enabling the safety message exchanges from the roadside unit (RSU) to its corresponding onboard unit (OBU) to reach the desired efficiency and performance levels.[6]

Lesson 3: Cost per unit decreases over time as supply chains grow to meet demand – Experiences from early pilots such as AASPMD demonstrated that cost per device was high due to the limited availability of vendors and qualified expertise. Some of the early DSRC vendors such as Savari were start-ups at the time and invested significant resources to develop RSU and OBU prototypes[7].  As testing continued and more pilot deployments emerged, the DSRC prototypes matured in technology readiness thanks to growing technical expertise from the start-ups as well as their larger competitors – leading to the development of a robust supply chain that helped lower the cost per unit. C-V2X may follow a similar path, where growing deployments in 4G-LTE (and eventually, 5G-NR) drive the demand for devices and over time, lowers the cost per unit as the industry increases production to meet growing demand.

Operating in 30 MHz of Spectrum

While lessons from DSRC pilot deployments offer a template for approaching C-V2X development, the ITS industry has a new task at hand: learning to operate in 30 MHz of spectrum. The reduced spectrum environment changes how ITS is operated and creates a different set of questions that C-V2X researchers will have to answer as its develops towards technology readiness.

Existing pilot deployments will likely face increased spectrum interference from unlicensed radio devices while new pilot deployments may experience longer licensing approval times, which can delay their aspirations for conducting testing activities. And while the ITS application layer may be re-usable from DSRC to C-V2X, some applications are at risk of being eliminated. These include advanced vehicle-to-pedestrian (V2P) applications[8] which are critical to enhancing the safety of vulnerable road users and may be unlikely to fit within 30 MHz of spectrum.

Looking Ahead: Embracing a Changing Regulatory Environment

As the ITS industry adapts to the changing regulatory environment, IOOs must be vigilant of additional changes to come as the FCC Safety Band ruling becomes more defined over the next few years. The recent publishing of the First Report & Order (R&O) in July 2021 has set off a chain of events that will likely define the future of V2X and impacts to ITS deployments at large.

Over the next year, ITS deployments for both DSRC and C-V2X can continue operating in 75 MHz of spectrum while also sharing with unlicensed radio devices in the lower 45 MHz of spectrum. At the conclusion of this one-year period, IOOs must vacate ITS operations from the lower 45 MHz of spectrum completely and transition into the upper 30 MHz of spectrum that allows for both DSRC and C-V2X. It is expected that this 30 MHz mixed standard-environment will continue until the 2^nd R&O is published, which sets off a two-year countdown towards a 30 MHz, C-V2X only environment and puts pressure on IOOs to accelerate plans for adapting their ITS deployments to meet new requirements.

Understanding how to deftly navigate these changes and acting strategically will be key to achieving results in the future. IOOs can learn from the 33 Smart Mobility Corridor, which has recently been working with Deloitte to develop an ITS Roadmap that outlines the changes and provides guidance on when and how to act based on the regulatory and market signals for ITS deployments. This can help remove the decision paralysis surrounding these changes and enable IOOs to move towards a safer transportation system that is connected and automated.