Relocating V2X to Better Spectrum Will Benefit Consumers

The FCC has proposed reallocating the lower 45 megahertz of the 5.9 GHz band for unlicensed use and retaining 30 megahertz exclusively for auto safety use. A 20 megahertz channel would be assigned for C-V2X operations and, tentatively, a 10 megahertz channel would remain for DSRC. Segmenting the band in this manner would add exactly the spectrum that Wi-Fi needs, when combined with adjacent unlicensed spectrum (the U-NII-3 sub-band), to provision the first and only unencumbered, gigabit-fast Wi-Fi channel. As beneficial as this single 160 megahertz channel would be, there is an option that could benefit consumers more: The commission could open all 75 megahertz of the 5.9 GHz band for unlicensed use and move the allocation of 30 megahertz for ITS auto safety operations to another band better suited for long-term automotive and public safety communications services.

If an alternative band is available, it could provide C-V2X with more spectrum, better propagation, and a less intensively-used spectrum environment in adjacent bands, making the relocation of the ITS safety band an even more robust win-win for consumers and the U.S. economy. Moving C-V2X operations to another band could also better harmonize C-V2X services with mobile 5G networks and the development of future connected car applications, both commercial and safety-related. We discuss below the very underutilized 4.9 GHz public safety band—50 megahertz of prime mid-band spectrum—as a leading candidate in this regard.

A critical aspect of the debate over the future of the 5.9 GHz band is public safety and specifically: How much of what type of spectrum is required for real-time vehicle safety communication? Although it’s understandable that the auto industry and DOT would prefer to maintain the “option value” of 75 megahertz at 5.9 GHz, in reality V2X technology for critical auto safety communications does not need even half of the 75 megahertz currently allocated for ITS at 5.9 GHz. This is clear from the conclusions of regulators in Europe, Japan, and even from the rationale for the DOT’s abandoned proposal for a DSRC mandate.

As noted above, regulatory agencies around the world have concluded that 30 megahertz or less is sufficient for V2X safety communications. Japan has allocated one single channel of 10 megahertz for DSRC that, as the commission notes in its NPRM, has “successfully and actively used for collision avoidance around intersections.”¹ The European Union long ago allocated 30 megahertz for one harmonized ITS channel.² More recently, as the commission’s 5.9 GHz NPRM also notes, the EU concluded that 30 megahertz is all that is required for real-time auto safety operations even if DSRC and C-V2X deployments coexist in the same spectrum band.³ A 2019 EU report that considered a possible expansion of frequencies to support both auto and rail ITS applications, concluded that “[t]here is no evidence that spectrum availability is currently a constraint on the development of ITS.”⁴

In its Europe-based advocacy, 5GAA (the coalition of auto and mobile industry supporters of C-V2X) acknowledged the ability of the two V2X technologies to both achieve real-time V2V safety signaling and coexist within a 30 megahertz allocation (in Europe, 5875-5905 MHz), initially relying on exclusive 10 MHz channels, and later sharing the total of 30 megahertz the EU has allocated for V2X safety. The group‘s 2018 whitepaper touts the ability of ITS-G5 (the 802.11-based equivalent of DSRC) and C-V2X to eventually share the entire 30 megahertz the EU has decided to allocate using detect-and-avoid. 5GAA proposed a spectrum sharing solution based on technology detection and dynamic frequency/channel selection—to be agreed among the stakeholders—to be implemented in up to three steps.”⁵ 5GAA described a two-step evolution to band sharing on 30 megahertz:

In all steps, each of C-V2X and ITS-G5 can operate safety-related ITS services free from co-channel interference from the other technology. The difference between the distinct steps lies in the overall usage of the spectrum resource: In the short-term first step, we propose to specify preferred 10 MHz channels at 5875-5905 MHz to each of the two technologies, while in the longer term third step, the solution will allow full sharing of all available channels [30 MHz] by the two technologies.⁶

5GAA has also told the commission that its testing “demonstrate[s] C-V2X’s ability to deliver important safety messages over a 20 MHz channel.”⁷ This is twice the bandwidth that NHTSA proposed in its 2016 NPRM for a V2V mandate relying on DSRC.

NHTSA itself essentially acknowledged that only 20 or 30 megahertz is needed. The DOT mandate for DSRC, since abandoned, would have required all V2V crash-avoidance signaling (Basic Safety Messages, or BSMs) to be transmitted on a single 10 MHz channel and on a radio separate from other non-critical ITS communications. As NHTSA explained:

Testing for DSRC will likely require procedures to establish both that the DSRC unit itself is able to receive and transmit the needed messages as timely as needed and without being compromised (recognizing that in the current design, one radio will be used exclusively for sending and receiving BSMs, while the other will be used to communicate with infrastructure and the security system), and that the BSM elements are accurate.⁸

Moreover, the auto industry has now essentially conceded it will not voluntarily commit to the sort of ubiquitous deployment of C-V2X that NHTSA has previously found would be necessary to even determine if the technology will be effective. For example, the Alliance for Automotive Innovation, in an April 2020 letter to the DOT and FCC, committed to deploy at least 5 million radios on “vehicles and roadway infrastructure” within 5 years if the FCC preserves all 75 megahertz of the 5.9 GHz band for safety.⁹ WifiForward observed that if the industry met this goal, “less than 2 percent of all cars on the road would be equipped with one of two competing V2X technologies, which means a motorist’s chance of encountering another car equipped with a compatible V2X device in a crash-imminent situation is less than one in a hundred.”¹⁰ That is exactly why NHTSA concluded that without a mandate, not even the single 10 megahertz channel it proposed to dedicate to basic V2V signaling would be put to effective use.

Although the auto industry understandably would like additional free, exclusive-use spectrum for non-critical driving and commercial applications, it would be more consistent with a path to 5G network convergence and the broader public interest to use a combination of unlicensed spectrum and bands other than 5.9 GHz, as we explain in the next section.

As part of the FCC’s fresh look NPRM, there remains the possibility of moving ITS auto safety operations—and particularly C-V2X—to a different and potentially superior band of spectrum. As Pai has previously noted: “As we evaluate the future of the 5.9 GHz band, we’ll need to consider what the future of automotive safety technology is likely to look like and the spectrum needs of such technologies, including whether they will require specifically dedicated airwaves.”¹¹ The consideration of the future of automotive safety technology should include the potential relocation of these operations to a new spectrum band.

As noted just above, the FCC acknowledges there is a global consensus that 30 megahertz is the amount of spectrum needed to protect auto safety. Finding a location for this auto safety communications—including a band that will promote the ultimate integration of C-V2X with 5G connected car capabilities and general purpose mobile 5G networks more generally—will require detailed review, coordination and testing. We are not in a position to say with certainty what alternative spectrum could work as well or better for C-V2X when it is ready for deployment. However, the 4.9 GHz public safety band appears to offer a viable alternative as a new, dedicated home for C-V2X and transportation safety more broadly that should be seriously considered by industry, DOT and the commission.

If DSRC did not already occupy the 5.9 GHz band, there is little likelihood that the commission in 2020 would even seriously consider allocating the 30 megahertz from 5895 to 5925 MHz to an exclusive public safety vehicle communication system. The spectrum ecosystem has shifted markedly since the commission first allocated the 5.9 GHz band for auto safety communication and DSRC. In 1999, the 5.9 GHz band was not considered valuable for personal communication. But today the band sits immediately between the current and future most valuable and intensely used bands for high-capacity Wi-Fi: the U-NII-3 band (5725-5850 MHz) and the U-NII-5 band (5925-6425 MHz).

An additional consideration, noted in the previous section, is the extreme uncertainty that even C-V2X will be deployed in every new vehicle and added to roadside infrastructure at a scale that will make it reliable as an automated safety communication system. The deployment of a ubiquitous V2V or V2X safety signaling system is by all accounts unlikely and at least two decades away. This is not our opinion, but rather the logical conclusion of findings by DOT and NHTSA in the run-up to the proposed DSRC mandate that is no longer planned.

First, as the NHTSA has acknowledged, DSRC (and, presumably, C-V2X) will not be reliable as an automated safety signaling network in the absence of a regulatory mandate, a proposal the DOT has abandoned.¹² NHTSA itself estimated that mandating DSRC would cost an extra $5 billion each year and that by 2060 the total costs would be $108 billion.¹³ Will every vehicle manufacturer voluntarily add this to the cost of every new vehicle? Extending this system to roadside infrastructure (V2I) entails an additional and enormous unfunded mandate on local governments with limited resources and basic roadway maintenance deficits, as the Government Accountability Office reported to Congress.¹⁴ Will thousands of local jurisdictions deploy the interoperable roadside infrastructure that characterizes a true V2X ecosystem?

Second, even with a government mandate, the technology was not expected to permeate the broader market for decades. In 2014, NHTSA released a comprehensive report on the viability of V2V that concluded: “Even if the market drives faster uptake by consumers of aftermarket devices (if, for example, auto insurance companies offer discounts for installing the devices), which would increase the ability of V2V devices to find each other earlier on, it will still take 37 years before we would expect the technology to fully penetrate the fleet.”¹⁵

C-V2X, which is still under development, is a particularly good candidate for different and ideally better spectrum. C-V2X technology is not compatible with DSRC services and is in no way tethered to the 5.9 GHz band, as the commission itself acknowledges.¹⁶ In fact, as the 5GAA coalition of mobile carriers and automotive companies have pointed out, one goal of C-V2X technology is eventual integration with general purpose 5G mobile networks, which can also extend its functionality with a wide range of connected car applications and services.¹⁷ The set of applications that come with C-V2X are being developed for eventual integration with mobile 5G networks and commercial connected car applications and services. 5GAA maintains that the “C-V2X protocol provides an evolutionary path to 5G and subsequent wireless generations that will amplify and expand upon the safety and other driving applications.”¹⁸ This would serve the public interest, if it ever happens. Nonetheless, the rapid emergence of C-V2X technology as a slice of 5G mobile networks that will rely on hundreds of megahertz of licensed and unlicensed spectrum in other bands suggests that an exclusive allocation at 5.9 GHz is not necessary.

One option for an alternative and potentially better band of spectrum for ITS operations, and C-V2X specifically, is the 4.9 GHz band, an extremely underutilized band already allocated for public safety operations. The commission noted in its 2018 Further Notice of Proposed Rulemaking on underutilization of the 4.9 GHz band that at most 3.5 percent of potential licensees use the band: “Although nearly 90,000 public safety entities are eligible under our rules to obtain licenses in the band, there were only 2,442 licenses in use in 2012 and only 3,174 licenses in use nearly six years later in 2018.”¹⁹ Active use of the band may be considerably less than even the number of licensees suggest. In his 2018 statement marking the adoption of the most recent 4.9 GHz FNPRM, O’Rielly lamented that the band is “woefully underutilized” and “it is way past time to take a fresh look at this 50 megahertz of spectrum.”²⁰

Under current FCC rules, public safety agencies receive a geographic “jurisdictional license” that authorizes them to deploy a wide range of applications, including both fixed and mobile applications, without filing separate applications or information on deployments. Fixed point-to-point links (for data backhaul), temporary fixed links (e.g., for incident management), meshed networks (primarily for wide area video surveillance), local hotspot use, air-to-ground communication, and mobile broadband operations are all allowed on a co-primary basis and with no requirement for frequency coordination.

Reports on the band by both the National Public Safety Telecommunications Council (2013) and by APCO International (2015) recommended a more formal process for frequency coordination, stating that many agencies were reluctant to deploy in the band because of the lack of information about what other agencies had deployed that might cause interference.²¹ While some jurisdictions, including Los Angeles and New York City, voluntarily coordinate among agencies, most do not. The NPSTC report stated: “Given the jurisdictional licensing, there is a lack of clarity on where channels in the 4.9 GHz band are actually being used and where they could be assigned to additional eligible licensees who may need to use the spectrum.”²² The FCC’s proceeding to consider changes to the band remains pending.²³

The gross underutilization of the 4.9 GHz public safety band creates an opportunity to consider whether the spectrum could be more intensively used in whole or part for V2X operations, as the Dynamic Spectrum Alliance, a coalition of large high-tech companies, explained in a recent filing.²⁴ The band plan could possibly accommodate a consolidation of incumbent public safety use, particularly fixed wireless uses. The 4.9 GHz band is divided into ten one-megahertz channels and eight five-megahertz channels, and the commission rules limit channel aggregation bandwidth to 20 megahertz.²⁵ Moreover, as the APCO Task Force Report stated, it is “important to note that at present over 90 percent of the utilization is for point-to-point applications.”²⁶ If this remains true, it could be possible to coordinate those links locally to coexist on a particular 20 megahertz segment of the band. There are also several other very large licensed bands (e.g., in the 6 GHz and 11 GHz bands) where fixed point-to-point links can receive exclusive rights and interference protection.²⁷ This would address the complaint of public safety associations that because the 4.9 GHz band today is uncoordinated and subject to mixed fixed and mobile use cases, it is unreliable with respect to interference protection.

In contrast to proposals that limit ITS to the 5.9 GHz band, the consideration of 4.9 GHz (or other bands) would give the commission additional options to optimize the overall public interest outcome with respect to both auto safety and wireless broadband connectivity. For example, the commission might authorize the DSRC basic safety messaging channel to operate in 5.905- 5.915 GHz (Channel 184) and authorize new C-V2X operations in the lightly-used 4.9 GHz band. As the NPRM proposes, C-V2X systems in 4.9 GHz might initially be limited to the 20 megahertz that the 5GAA has stated they need for critical safety communications. And once C-V2X safety signaling is actually deployed and viable on its requested 20 megahertz channel, the commission could decide to expand 5G-interoperable ITS, either at 4.9 GHz or in another band, thereby allowing C-V2X to evolve toward its eventual integration with general purpose mobile 5G networks.

Another band that could be considered as a superior location for C-V2X auto safety communications is 3450-3550 MHz, a federal radar band currently being studied for potential clearing or sharing for commercial mobile use. As former National Telecommunications and Information Administration Administrator David Redl has noted, the NTIA and Department of Defense identified this 100 MHz of spectrum as a potential new band for wireless broadband.²⁸ The FCC advanced a proposal in December 2019 to review making this spectrum available for expanded mobile wireless use.²⁹ If eventual studies and tests of this spectrum find that the band can be cleared or even shared, then this band could merit further study for auto safety and V2X purposes, even if just a portion of it. Moving C-V2X services, which are based on 5G technology, to the 3450-3550 MHz band could also benefit the wireless industry, as it would place C-V2X deployments in a band immediately adjacent to another 5G mobile band.