Evaluation and Synthesis of Connected Vehicle Communication Technologies (2021) / Chapter Skim
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Page 9 V2X COMMUNICATIONS IN THE 5.9 GHZ SPECTRUM: March 2020 Update Contents Summary ..................................................................................................................................................... 10 Introduction ................................................................................................................................................ 11 Section 1 ‐ 5.9 GHz Spectrum Time Line ..................................................................................................... 12 Foundational Development Period ......................................................................................................... 12 Moving from Development to Deployment ........................................................................................... 13 Progress Versus Uncertainty ................................................................................................................... 15 Special Temporary Authority .................................................................................................................. 16 Section 2 ‐ FCC NPRM to Reallocate the 5.9 GHz Spectrum ....................................................................... 18 Summary of the Process ......................................................................................................................... 18 Overview of Comments Submitted to the FCC on the Current NPRM ................................................... 19 Submitters ........................................................................................................................................... 20 Key Issues from Infrastructure Owners and Operators ...................................................................... 21 Key Issues from Other Transportation and Infrastructure Stakeholders ........................................... 22 Key Issues from Original Equipment Manufacturers (OEMs) and Suppliers ...................................... 22 Key Issues from the Trucking and Commercial Vehicle Industry ........................................................ 23 Key Issues from Technology Companies Also in Opposition to the NPRM ......................................... 23 Key Issues from Current Secondary Spectrum Users .......................................................................... 24 Comment Spotlight: Keep the Spectrum, but Consider a New Approach .......................................... 25 Comment Spotlight: Legal Arguments ................................................................................................ 26 Key Issues in Support of the NPRM ..................................................................................................... 27 Section 3 ‐ Overview of Critical Terms and Testing Outcomes ................................................................... 29 Terms and Concepts ................................................................................................................................ 29 Current 5.9 GHz Spectrum and its Utilization ......................................................................................... 30 Introduction of C‐V2X ......................................................................................................................... 31 How the Post‐NPRM Spectrum Appears ............................................................................................. 32 Published Test Results on Interference .................................................................................................. 33 Published Benefits Analyses ................................................................................................................... 34 Conclusions ................................................................................................................................................. 37 Appendix A ‐ Technical Information ........................................................................................................... 38
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Page 10 V2X COMMUNICATIONS IN THE 5.9 GHZ SPECTRUM: March 2020 Update Summary This white paper is focused on the 5.9 GHz spectrum and the important role it has played -- and will continue to play -- in achieving the many safety and efficiency goals originally established when 75 MHz of the band was first set aside for intelligent transportation system (ITS) services. Connected vehicle applications made possible by the existence of this dedicated radio frequency band can -- and will -- be a difference‐maker in future transportation systems. The National Highway Traffic Safety Administration (NHTSA)
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Page 11 Introduction Connected Vehicle (CV) technologies enable all types of vehicles, roadways, and mobile devices to communicate and share vital transportation information. Several new and evolving mediums can provide high‐speed low‐latency communication that will enable a host of applications categorized as vehicle‐to‐vehicle (V2V)
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Page 12 Section 1 ‐ 5.9 GHz Spectrum Time Line As an investment in the development of a safer transportation network to further the goals of Congress, the U.S. Department of Transportation (USDOT) , and the ITS industry, the FCC allocated 75 MHz of spectrum in the 5.9 GHz band for intelligent transportation services in 1999. This was envisioned to improve traveler safety, decrease traffic congestion, and facilitate the reduction of air pollution while conserving fossil fuels. The FCC understood this was an investment that would require further effort and investigation from several stakeholders.3 As shown in Figure 1 below, the timeline for the 5.9 GHz spectrum evolution has passed through several major milestones over the past two decades. They can best be described as the Foundational Development period, Moving from Development to Deployment, and Progress Versus Uncertainty. Figure 1 ‐ Graphical Representation of the 5.9 GHz V2X Timeline (source: WSP USA)
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Page 13 The FCC began accepting applications for licenses and issued the first DSRC licenses in October 2004. (Note that despite the first license being issued, deployment was still not possible until 2008 as noted below) . From 2004 to 2006, the industry continued working with USDOT and the FCC on the designation of two channels within the 5.9 GHz Band for the highest priority vehicle safety communications, specifically using DSRC. During this period the USDOT also began aggressively pursuing a "proof of concept" test in Southeastern Michigan, to work through various deployment issues including system architecture and the design of systems, subsystems, and components, as well as the public sector applications developed to prove some of the system concepts. The FCC Explicitly noted a spectrum sharing agreement had not yet been reached between the transportation industry and incumbents, in its July 2006 Memorandum Opinion and Order regarding the channel designation. This was the one remaining regulatory barrier to actual DSRC deployment. Led by ITS America and AASHTO, an agreement between the transportation industry and Satellite Industry Association was submitted to the FCC in February 2008. Almost 10 years after the initial spectrum allocation, this agreement marked the first time that V2X technologies could be deployed unencumbered by a lack of standards or the threat of interference. Moving from Development to Deployment From 2008 through 2017 many critical industry standards, product specifications, and security protocols were developed for DSRC. Some were accomplished through numerous USDOT‐funded research and prototype programs to standardize safety‐critical infrastructure elements, such as signal phase and timing and maps, as well as safety/mobility applications that further the role and value of DSRC. Many of these were public‐private partnerships or brought in significant private industry engagement to assure that the technologies, applications, and standards would be industry‐ready quickly. Simultaneously, USDOT was actively engaged with private sector Standards Developing Organizations (SDOs)
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Page 14 brought us closer to a stage of "industry‐ready" status.7 A graphic representation of the project is shown in Figure 2. Figure 2 ‐ Safety Pilot Model Deployment Overview (source: UMTRI) At the same time the Safety Pilot Model Deployment was showing great promise, in February 2012, Congress passed the Middle‐Class Tax Relief and Job Creation Act of 2012. This Act included a provision requiring the National Telecommunications and Information Administration (NTIA)
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Page 15 that would be made possible by V2X communications. This was an important launching point as many infrastructure agencies around the nation began to contemplate V2X deployments in their states. While DSRC progress was rapidly expanding, in 2014 the 3rd Generation Partnership Project (3GPP) , a collaborative project aimed at developing globally acceptable specifications for third generation (3G)
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Page 16 Not long after Toyota's announcement, two FCC Commissioners issued an unprecedented letter to Toyota signaling the FCC's interest in opening the 5.9 GHz band for unlicensed use.9 Later in 2018, the FCC released its Phase I Testing Report, and sought comments on the report, in October 2018. The next month, the 5G Automotive Association (5GAA) petitioned the FCC for a waiver to allow C‐V2X to operate in Channels 182 and 184, the upper 20 MHz of the 5.9 GHz band, leaving the remaining channels for DSRC. And the Ford Motor Company announced plans for widespread installation of C‐V2X in upcoming model years. More than any other year, 2018 represented the "progress versus uncertainty" period. During several speeches in 2019, FCC Chairman Ajit Pai referred to the 5.9 GHz spectrum as "lying fallow," and to DSRC as a "promise unfulfilled."10 And in April of that year, Toyota announced it would halt its plans to install DSRC across its vehicle fleet as announced only a year earlier. Toyota said the decision was based on "a range of factors, including the need for greater automotive industry commitment as well as federal government support to preserve the 5.9 GHz spectrum band for DSRC."11 In late 2019, FCC Chairman Pai announced that the Commission intended to release a Notice of Proposed Rulemaking (Docket 19‐138)
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Page 17 existing licensees." The providers must contact any potentially affected license owners before beginning operation, but if a "complaint of interference cannot be timely resolved, operation under this STA must cease." At the conclusion of the 60‐day STA, providers must "cease operating in the 5.9 GHz band and retune equipment to operate in compliance with the Commission's equipment certifications."
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Page 18 Section 2 ‐ FCC NPRM to Reallocate the 5.9 GHz Spectrum In December 2019, the FCC approved a Notice of Proposed Rulemaking (NPRM) that would reduce the safety spectrum set‐aside for CV technologies from 75 MHz to only 30 MHz, establish specific technology requirements within that allocation, and open the rest of the spectrum to unlicensed Wi‐Fi devices (FCC ET Docket No. 19‐138)
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Page 19 The time from closing of comment windows to FCC action can vary greatly, with both internal and external factors influencing the timing. Likewise, the volume and nature of comments may or may not impact timing. During this period, FCC staff continues to take meetings with interested parties to have additional discussions. Summary briefs of these meetings will be published as ex parte communications on the FCC website. There are many possible outcomes from the NPRM, but the most likely actions by the FCC are: 1. Issue a revised Report and Order that causes an action to be adopted that may or may not track exactly with all that is included in the NPRM; 2.
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Page 20 reduced fatalities and injuries be considered under the FCC's mandate to allocate radio spectrum in the "public interest". Notably, among submitters in the transportation industry who voiced opposition to the NPRM, 80% were either technology neutral, did not mention DSRC or C‐V2X in their comments, or encouraged the provision of bandwidth for both technologies. Of the minority who expressed preference for a specific technology, 14% favored DSRC and 6% favored C‐V2X. Submitters A wide variety of submissions were received: The American Automobile Association, American Road & Transportation Builders Association, American Society of Civil Engineers, International Bridge, Tunnel and Turnpike Association, Institute of Transportation Engineers, ITS America, National Transportation Safety Board, Society of Automotive Engineers (SAE) , and the National Safety Council all submitted comments.
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Page 21 spectrum to support existing communication network infrastructures, particularly in emergency and disaster situations. Additional entrants in opposition to the NPRM included the National Sheriffs' Association, International Association of Fire Fighters, National School Transportation Association, various bicycling and walking advocacy organizations, groups interested in the efficiency enhancements such as Securing America's Future Energy, industry groups like OmniAir, and safety organizations like the Vision Zero Network. USDOT submitted a significant amount of additional information in opposition to the NPRM, by way of the United States Department of Commerce National Telecommunications and Information Administration. Technology companies Broadcom, Facebook, Comcast, and Microsoft, and various associations including Citizens Against Government Waste, the Wireless Internet Service Providers Association, the Open Technology Institute, Public Knowledge, and the Internet & Television Association provided both comments and ex parte submissions in support of the NPRM. Key Issues from Infrastructure Owners and Operators Submissions from state and local transportation agencies and other key associations were strongly united in opposition to this NPRM. They frequently raised several common issues. Some of these include: This action is shortsighted, given that 37,000 people are dying annually on our nation's roadways and this technology has the potential to reduce that number by up to 80%. Many jurisdictions are committed to Vision Zero goals; this action is in direct contradiction. Public safety should be valued over potential commercial advancement. The safety, as well as mobility and efficiency benefits, of using this spectrum for V2X need to be more carefully considered and analyzed. Rather than only considering the potential economic opportunities of opening the spectrum to unlicensed use, the FCC should also weigh the direct costs associated with crashes (estimated at over $800 billion in 2017) and traffic congestion ($140 billion)
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Page 22 mature standards like DSRC does, though they seemed open to testing dual‐units or following a phased approach that allows new technology to be adopted without sacrificing existing investments during the lifetime of existing equipment. Key Issues from Other Transportation and Infrastructure Stakeholders Many vendors, consultants, and academics echoed those of state and local DOTs, and included the following highlights: Safety is the top priority, and the benefit to society of 45 MHz of additional Wi‐Fi spectrum is small compared to the value of additional road safety. 30 MHz is not enough, and more research needs to be done on potential spectrum interference.
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Page 23 advanced ITS applications including platooning, traffic flow coordination for congestion management, and automated valet services for parking management. The opportunity to use the enormous supply of data of CAVs to save lives is what has motivated an estimated $80‐billion of investment in automated vehicles between 2014 and 2017 alone. This proposal risks stifling technological innovation. Toyota points out that in the NPRM, the FCC proposes repurposing at least 20 MHz away from DSRC to C‐V2X. However, it does not specify whether the C‐V2X technology that it is proposing to be used is LTE V2X or 5G NRV2X. Since 5G NR V2X is not capable of same‐channel coexistence with LTE V2X (and is not backwards compatible) , a decision to permit LTE V2X in a channel locks in LTE V2X as the only C‐V2X technology that can be used in that channel -- now and into the future. Sufficient bandwidth is not optional, or nice‐to‐have, it is essential to automotive safety in this context. When it comes to saving American lives, we should clearly strive to be the global leader. Key Issues from the Trucking and Commercial Vehicle Industry The trucking industry raised many of the same points as other stakeholders, including: Utilizing advanced vehicle technology will enhance both the safety of employees and of the general public, particularly in today's challenging operating environment for large trucks. One of the near‐term applications of these technologies is platooning of two or more tractor‐ semitrailer combination vehicles. This could help decrease traffic congestion, reduce emissions and air pollution, and enhance safety. This proposal will harm highway, road, and bridge safety. Recommend coordinating more closely with USDOT to study implications. While some previous estimates of the timing of transportation‐related use of these technologies may have been overly aggressive, the future widespread benefits of the technologies should not be underestimated. Key Issues from Technology Companies Also in Opposition to the NPRM Beyond infrastructure and automotive stakeholders, several wireless and technology companies also came out in opposition to the NPRM as currently structured. Their comments included: Qualcomm continued its support for C‐V2X over DSRC, but agreed that 30 MHz is not enough to deploy potential applications fully. Panasonic supported a technology‐neutral approach as it has supported both DSRC and C‐V2X deployments and urged the FCC to undergo a more rigorous analysis that considers the billions of dollars in economic impact provided by lifesaving V2X technologies, for which there are no currently viable substitutes. T‐Mobile and AT&T agreed that the public interest would be best served by designating the full 5.9 GHz band to ITS, though T‐Mobile voiced support for C‐V2X while AT&T remained technology neutral. Their justification included: o The Commission has already made sufficient additional spectrum available for unlicensed use. The U.S. is an outlier in making substantially more spectrum available on an unlicensed and shared basis than other countries.
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Page 24 o This can help enable important improvements in safety, traffic efficiency, mobility, and energy efficiency on America's roads. o Reallocating the lower 45 MHz of the 5.9 GHz band for exclusively unlicensed Wi‐Fi use would deliver only incremental public benefits and have a minimal impact on investment in the unlicensed device ecosystem.
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Page 25 Comment Spotlight: Keep the Spectrum, but Consider a New Approach While the automakers were not uniform on technology preferences (DSRC, C‐V2X, or both) , several of their submissions did state the need for stakeholders to coalesce around the broader goal of interoperability and focus on resolving any technical differences, while keeping the full 75 MHz. General Motors suggested that the FCC allow the transportation community (vehicle manufacturers and infrastructure owner‐operators)
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Page 26 Comment Spotlight: Legal Arguments Several submissions that opposed this NPRM have introduced legal arguments, suggesting that the FCC may lack the legal authority to implement this action. While these arguments might (or might not) influence the initial action taken by the FCC, they could potentially arise later as the basis of legal appeals if the NPRM should move forward as currently proposed. Legal Reference Issue Summary from Submitted Comments Submitters The NPRM represents a "fundamental change" to existing DSRC licenses, which violates Sect 316 of the Communications Act (47 U.S.C.)
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Page 27 Legal Reference Issue Summary from Submitted Comments Submitters The USDOT, the expert agency on transportation safety, and dozens of other transportation experts and organizations, have presented evidence that contradicts the FCC's proposal. Key Issues in Support of the NPRM As noted earlier, a small number of commenters did support the NPRM as currently structured. Technology Associations Policy and Watchdog Organizations Private Companies NCTA ‐ The Internet & Television Association Wireless Internet Service Providers Association Dynamic Spectrum Alliance Wi‐Fi Alliance Citizens Against Government Waste Open Technology Institute The Free State Foundation R Street Institute Competitive Enterprise Institute Consumer Action for a Strong Economy, Inc.
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Page 28 The other comment stated that the Commission needs to reexamine the OOBE limit at the upper U‐NII‐4 band edge in a manner that protects the Vehicular Safety Service but does not restrict commercially important Wi‐Fi use cases. The proposed rule would significantly reduce or even eliminate the possibility of Wi‐Fi deployments in the band, and so the OOBE limit should be changed to match that of U‐NII‐3 devices.
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Page 29 Section 3 ‐ Overview of Critical Terms and Testing Outcomes The current NPRM and the comments that have been received by the FCC related to this proposed rulemaking include many terms and technologies that may not be familiar to those who aren't following it closely. Terms like U‐NII‐3 and U‐NII 4, interference and spectral masks, decibels (dB) , adjacent channels and re‐channelization, detect and vacate, and sensitivity -- to name just a few. Further, the reports documenting the results of testing activities that have been performed by the FCC, USDOT, CAMP, 5GAA and others introduce even more new terms and concepts. This section will serve to identify and define those elements which are key to understanding the issues and concerns of the proposed rulemaking. It will also summarize important features of the current legacy spectrum and give an overview of recent and relevant test activities critical to understanding the impact this NPRM might have on safety‐related applications. The high‐level discussion presented in this section is the result of detailed research and review of multiple sources representing many different entities and different viewpoints. Additional information related to these topics, the technology, testing, and results of that testing can be found in the appendix. Terms and Concepts Dedicated Short‐Range Communications (DSRC)
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Page 30 Interference is defined by any external source whose output overlaps the channel of the intended transmission and produces undesired effects in that band. Interference can be in one of three forms: ambient or background noise, packet collision, and transmitter message suppression. Ambient noise is the culmination of all unwanted signals, both in‐band and adjacent, which reduces the ability of weak signals from distant transmitters to be received. Ambient noise is typically a result of unlicensed devices transmitting in or near the DSRC channel. Packet collision occurs when a receiver receives packets simultaneously from two or more sources and the message cannot be properly interpreted, rendering them useless. These packets are discarded by the receiver. These are essentially transmitted messages that are lost. Transmitter message suppression, also known as Clear Channel Assessment, is a feature of DSRC whereby the transmitter waits until the channel is idle before transmitting. If the channel is not idle, the transmitter will wait a random period and then re‐try the transmission. In the case of DSRC, if secondary transmitters are continually using the channel and no idle period can be detected, the message transmission by the primary device will effectively be suppressed. While in this case the wireless radio is truly operating as designed, the effects are not desirable. Cross‐Channel Interference, also known as Adjacent Channel Interference, is another way to describe interference caused by out‐of‐band emissions infringing overlapping the channel of the intended transmission. Spectral Mask is a term used to define the shape of an RF transmission, including the relative power levels in and out of band. A more detailed discussion is included in the appendix. Signal Power is the amount of energy used to radiate (i.e., push) an RF signal. Power is measured in decibels (dB)
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Page 31 the lower end by a 5 MHz guard band. The Public Safety Channel, Ch. 184, at the upper edge of the band is afforded higher‐power transmission, negating the impact of adjacent channel interference. The Control Channel, Ch. 178, sits in the middle of the spectrum and given its role facilitating the management of the remaining four channels, mitigates interference as part of its channel use strategy. Figure 4 ‐ Channel Allocation for the 5.9 GHz Spectrum (source: WSP USA) Often overlooked when discussing spectrum utilization, the security elements, and the robust environment that has been developed to support security, have a critical need for a reliable way to exchange, renew, and revoke digital certificates. Without the ability to authenticate messages, the value of safety data is minimized. The use of service channels as prescribed in the present architecture allow for security and other critical operational features to be implemented without negatively impacting the exchange of safety‐critical information. Introduction of C‐V2X With the release of 3GPP Release 14 (R14)
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Page 32 How the Post‐NPRM Spectrum Appears If the recommendation of the FCC in the current NPRM is accepted, the channel configuration will undergo a significant change. As shown in Figure 5, the lower 45 MHz, which includes the 5 MHz guard band, and the first four DSRC channels, including both the Safety Channel, Ch. 172, and the Control Channel, Ch. 178, will all be re‐allocated to use by unlicensed Wi‐Fi. The upper 20 MHz of the spectrum will be dedicated to C‐V2X consistent with the waiver 5GAA filed with the FCC for initial use. That leaves a single, 10 MHz channel, Ch. 180, offered for either DSRC or C‐V2X operations, to be determined. Figure 5 ‐ FCC NPRM Channelization of Spectrum Reallocation (source: WSP USA) From the DSRC perspective, the thoughtful engineering to minimize adjacent channel interference is no longer possible; the ability to maximize spectrum use for all of the services envisioned for DSRC is not possible; and what remains is the possibility of a single channel that (according to USDOT research)
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Page 33 Published Test Results on Interference Exploration and testing of the 5.9 GHz and surrounding spectrum for interference and mitigating strategies is nothing new. In fact it was identified as early as 2010 when the notion of possible spectrum sharing came to light.
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Page 34 The design, test and activities necessary to engineer a robust environment with sufficient confidence to support ITS safety using DSRC required tens of thousands of hours and data points to produce. Observations: Adjacent channel interference from high‐power Wi‐Fi (36 dBm EIRP)
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Page 35 Emergency electronic brake light; Red light violation warning; Curve speed warning; Reduced speed/work zone warning; and High‐speed platooning. In terms of quantifying the benefits of connected vehicle technology, most analyses focus on its potential to improve safety, mobility, and sustainability. For example, the SPaT data that is broadcast at an intersection can address all three. Safety: The OBU can assess the vehicle will run a red light and warn the driver. Environment: Using the SPaT information from a corridor of RSUs, the OBU can direct the driver to maintain a specific speed such that the driver does not need to accelerate or brake while traversing a corridor. This increases fuel economy and decreases the carbon footprint. Mobility: Based on connected vehicle data, the traffic signal controller can dynamically adjust the SPaT to improve traffic flow and reduce congestion. Most benefit analyses that have been conducted to date, focus on the benefits of connected vehicle technology, but very few focus on the costs. Volpe completed an analysis in April of 201418 and found that V2I applications have a very large safety benefit potential, even when viewed as an incremental add‐on to V2V safety systems. They also found that V2I provides additional benefits during the years when OBU penetration is low because it can be available when only one vehicle (rather than both) is equipped. However, the cost‐benefit discussion in the document only included safety benefits. In December 2015, NHTSA published the results of the independent evaluation of V2V safety applications from the Safety Pilot Model Deployment.19 Volpe, the independent evaluator, concluded that overall, the Safety Pilot Model Deployment demonstrated that V2V technology can be deployed in a real‐world driving environment and that the safety applications issued warnings in the safety‐critical driving scenarios that they were designed to address. Several other research documents provide safety‐based deployment assistance location for curve speed warning,20 stop‐sign gap assist,21 and red light violation warning22 applications. The purpose of each of the documents is to give state and local agencies guidance on how to select locations for deployment for each of the three applications to derive the greatest benefit‐to‐cost ratios. 18 Volpe, Connected Vehicle Deployment Decision‐Support Analysis and stakeholder Impact Analysis: Summary of findings. April 11, 2014. https://www.transportation.gov/sites/dot.gov/files/2020‐03/CV%20Deployment%20Decision%20Support%20‐ %20Summary%20Report%20final_0.pdf 19 Nodine, E., Stevens, S., Lam, Andy, Jackons, C. and Najm, W. Independent Evaluation of Light‐Vehicle Safety Applications Based on Vehicle‐to‐ Vehicle Communications Used in the 2012–2013 Safety Pilot Model Deployment. NHTSA. December 2015. DOT HS 812 222. 20 Safety‐Based Deployment Assistance for Location of V2I Applications Pilot: Curve Speed Warning Application. https://www.transportation.gov/research‐and‐technology/safety‐based‐deployment‐assistance‐location‐v2i‐applications‐pilot‐curve 21 Safety‐Based Deployment Assistance for Location of V2I Applications Pilot: Stop‐Sign Gap Assist Application. https://www.transportation.gov/research‐and‐technology/safety‐based‐deployment‐assistance‐location‐v2i‐applications‐pilot‐stop 22 Safety‐Based Deployment Assistance for Location of V2I Applications Pilot: Red‐Light Violation Warning Application. https://www.transportation.gov/research‐and‐technology/safety‐based‐deployment‐assistance‐location‐v2i‐applications‐pilot‐red
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Page 36 Another study from the University of Michigan Transportation Research Institute23 illustrates the negative consequences of delaying deployment of DRSC. It also reinforces the need for FMVSS 150, the proposed regulation that would have mandated V2V technology in all light weight vehicles, but was put on long‐term action list during an administration change. In addition to the technical research mentioned in the previous section, a significant difference of opinion is growing in terms of cost‐benefit analysis concerning the use of this spectrum. A number of commenters to the FCC NPRM noted that the benefits and costs section of the NPRM is "extraordinarily one‐sided," focusing almost exclusively on the benefits of making additional spectrum available to unlicensed use while largely ignoring the benefits that are lost by reallocating 45 MHz away from transportation safety. The FCC references a RAND study's estimates in terms of consumer surplus and revenue growth (the same as GDP, fn. 96) . At $17.7 billion for 75 MHz, this estimate is much smaller and by implication smaller still for 45 MHz at $10.6 billion ($17.7 billion x 0.6)
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Page 37 Conclusions V2X applications enabled by the 5.9 GHz spectrum have traversed a deliberate time line that featured a developmental period, testing period, and the current period of regulatory uncertainty. Feedback submitted to the FCC concerning their proposed reallocation of the 5.9 GHz spectrum was significantly in opposition, with safety and radio interference raised by many submitters. This white paper summarized comments from several different stakeholder groups, and highlighted several areas that might be of interest (including suggestions for how to move forward, and information on possible legal challenges that could be pursued by some of the submitters) . The current NPRM and the comments that have been received by the FCC have also brought new technical research and terminology to the dialogue, and this white paper has provided an overview that demonstrates the need for additional radio interference research, as well as cost/benefit analyses. Additional technical information on the technology, testing, and results of that testing can be found in the appendix.
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Page 38 Appendix A ‐ Technical Information Section 3 of this white paper provides a high‐level discussion on several key elements related to the technologies operating (or planning to operate) in the 5.9 GHz spectrum. To support the understanding of those discussions, Section 3 also defines many key terms using familiar terminology. The background and detailed information in this appendix is intended to provide additional depth to the conversation, taking a deeper dive on some or all of those supporting elements, elements that were fleshed out in great detail during the drafting of this paper. The order generally follows the order of Section 3, expanding on many of the summary items documented in the main body, and including additional information that was purposefully omitted from the body of the paper. Some repetition is necessary in order to ensure the context of the original language is maintained. While not meant to be standalone document, a majority of the subsections in this appendix are able to be read as such. Current 5.9 GHz Spectrum and its Utilization When the 5.9 GHz spectrum was first allocated to USDOT for ITS, engineers were very purposeful in their design of DSRC devices to maximize the use of the spectrum and minimize the effects of interference. Message exchanges needed to work well in an environment where the sender and a receiver may be moving toward or away from one another at speeds greater than 100 miles per hour, or where vehicles are moving at varied speeds in the same environment. To maximize the number of vehicles that can reliably communicate with each other and with the infrastructure, engineers considered the entire 75 MHz of the 5.9 GHz band. The result is the current DSRC design with seven (7)
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Page 39 Table 1. Channel Use by DSRC (Source: WSP USA) 172 (Safety Channel)
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Page 40 The IEEE 1609.3 Wireless Access for Vehicle Environments (WAVE) Service Advertisements (WSA)
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Page 41 respects. With V2X, however, much information can be gleaned from the data our vehicles broadcast. Since most of the data broadcast by our vehicles are critical to the operation of vehicle safety applications and broader mobility applications, V2X security focuses on privacy protection -- protecting the identity of the vehicle operator and owner. V2X messages do not contain PII or vehicle identifiable information (VII) , such as vehicle make, model, model year, or vehicle identification number (VIN)
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Page 42 Twice a year, OmniAir hosts a "PlugFest", in which device manufactures, test laboratories, and test equipment manufactures come together to evaluate their devices against OmniAir's certification test processes. PlugFest enables device manufactures and test equipment providers to conduct certification dry runs in a safe and secure environment, prior to submitting devices for certification. Introduction of C‐V2X With the release of 3GPP Release 14 (R14) in 2017, a new technology supporting device‐to‐device communications was introduced. Known as Cellular Vehicle to Everything (C‐V2X)
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Page 43 Figure 6 ‐ C‐V2X Proposed Spectrum Plan (source: WSP USA) C‐V2X Security C‐V2X devices utilize the same IEEE 1609.2 certificates as DSRC devices. There is no difference between enrolling a DSRC device or a C‐V2X device in a SCMS or in the way the certificates are utilized by the devices and applications. OmniAir C‐V2X Device Certification The OmniAir Consortium is developing a C‐V2X certification program similar to their existing DSRC program. They are working with device manufactures, test laboratories, test tool manufactures, and other industry stakeholders to develop appropriate test cases, leveraging existing DSRC test cases and developing new test cases to meet relevant 3GPP R14, SAE J3161, and other requirements. OmniAir has been evaluating C‐V2X test cases since the 2019 spring PlugFest and plans to roll out the official program in the fall of 2020. Differences Between DSRC and C‐V2X The principal difference between DSRC and C‐V2X is the communication stack Radio (physical)
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Page 44 Figure 7. Comparison of DSRC and C‐V2X Network Stack V2X Support for Automated Vehicles As previously discussed, V2X devices are omnidirectional (i.e., offer 360 degrees of coverage) . Communicating via radio signals allows two equipped vehicles to "hear" each other and exchange critical information -- regardless of whether the vehicles are in view, around a corner, or behind a building or even a cornfield. This is a significant benefit for enhancing the safe operation of automated vehicle functionality and reliability. Without connectivity, automated vehicles are islands, much like traditional human driven vehicles are today. They do not coordinate their actions, nor do they cooperate with each other for the overall benefit of the "system." Vehicles with Radar, LiDAR cameras, and other sensors need to sense, or "see" their environment. They must: See (detect)
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Page 45 With connectivity, automated vehicles: Coordinate and cooperate with each other to improve overall traffic flow; Are no longer islands, they're part of a "system" (collective) ; Have enhanced situational awareness (visibility of environment)
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Page 46 C‐V2X 3GPP is developing a "New Radio" technology as part of Release 16, designated as "Advanced C‐V2X." The NR V2X standard is likely to employ a similar approach to the previously developed New Radio standard for base station communication (uplink/downlink) . However, the 3GPP decided in 2018 not to consider same‐channel coexistence between NR V2X and LTE V2X. Therefore, NR V2X is not backward compatible. This means that for some period of time, devices will require a dual radio system, one for R16 and one for R14, to support the new technology and the legacy LTE C‐V2X technology until all devices and installations move to the 5G NR, R16 capability. As with current DSRC and C‐V2X technologies, these differences are only at the radio level; SAE defined V2X messages, interfaces to other devices (e.g., Traffic Signal Controllers)
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Page 47 Advanced Terms and Concepts The primary source of concern for the proposed spectrum reallocation is the introduction of interference, interference that will limit the effectiveness of DSRC or C‐V2X. The following is a detailed discussion of key terms and concepts related to the types of interferences and what constitutes interference versus a normal waveform. Overview of Radio Frequency Interference Radio Frequency Interference (RFI) is defined as any external source whose output overlaps a signal path and produces undesired artifacts in the signal along that path. The impact of RFI can be far ranging, resulting in an increase in error rate or in the worst case, a total loss of data. When safety of life is dependent on receipt of messages from other vehicles and from infrastructure, as is the case with the current V2X use cases, any loss of data can have a significant impact. Forms of RFI RFI is generally thought of in one of three forms: ambient or background noise, packet collision, and transmitter message suppression. Separate or in combination, these forms of RFI prevent the reliable exchange of data between a transmitter and a receiver. The following describes each and their specific impact. Ambient noise is the culmination of all unwanted signals, both in‐band and adjacent, which reduces the ability of weak signals from distant transmitters to be received. Ambient noise is typically a result of unlicensed devices transmitting in or near the DSRC channel. Packet collision occurs when a receiver receives packets simultaneously from two or more sources and the message cannot be properly interpreted, rendering them useless. These packets are discarded by the receiver. These are essentially transmitted messages that are lost. Transmitter message suppression, also known as Clear Channel Assessment, is a feature of the Carrier Sense Multiple Access/Collison Avoidance (CSMA/CA)
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From page 48... ...
Page 48 power point or floor of the spectral mask is considered to be ‐40 dBr, a point where the power level has been reduced by 10,000 times. The second principle is to understand the characteristic of a radio frequency (RF) signal. As seen in Figure 8, this is a waveform for a typical U‐NII‐3 802.11ac signal. The waveform of a transmitted RF signal does not behave like a square wave with an infinite (completely vertical)
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Page 49 Published Test Results on Interference As noted in the main body of the white paper, five (5) key reports white papers served as the basis of our summary of the state of testing. The following is a brief overview and relevant findings from each of the document reviewed. The summary of the facts and observations from each may be found in the main body of the white paper. FCC Report TR 17‐006 – Phase 1 Testing Results The first significant result of spectrum sharing tests is embodied in FCC Report TR 17‐006, published in October 2018.29 This report captures the results and summarization of the completed Phase I testing as recommended in NPRM 16‐68 (June 1, 2016)
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Page 50 with vehicles moving at different speeds or directions. Data collected from these measures were also intended to inform a qualitative assessment of adjacent channel rejection of DSRC. Impairing Traffic Safety from Changes in the Safety Band: Introduction of Interference from Unlicensed Users This August 2019 Draft Report from USDOT, published in March of 2020, puts the impact of the prior and ongoing interference testing, and the proposed re‐channelization, into context by identifying the expected impact to the current, demonstrated spectrum use and resulting safety applications as provided by DSRC.30 This includes the exchange of BSMs between vehicles, as well as the use of SPaT and other safety‐critical messages. This report further explores the functional impact of re‐ channelization to the use of the service and control channels, as prescribed by the standards governing DSRC. When the approach to implementing DSRC was designed, particular attention was paid to how the 75 MHz spectrum was used to ensure that all of stated goals of this spectrum were used. In the process, specific uses were assigned to specific channels, and along with that power limits and spectral masks were developed for each channel, to ensure that they themselves would not interfere with one another. With the current FCC NPRM intending to compress all of the DSRC communications into a single 10 MHz channel, the RF design that had been performed previously and rigorously tested to ensure reliable and robust communications, without interference, is no longer applicable, and will require new design considerations and testing. USDOT DSRC‐U‐NII‐3 Sharing & Spectrum Interference Testing – Draft Report In March 2020, USDOT released the January 2020 Draft Report on USDOT DSRC‐U‐NII‐3 Sharing & Spectrum Interference Testing.31 Unlike FCC Report TR 17‐006 which used prototype U‐NII‐4 devices, devices that don't yet exist commercially, this report considers the impacts of existing Wi‐Fi devices, known as U‐NII‐3, if they are allowed to share or operate adjacent to DSRC in unlicensed spectrum. This report was intended to serve as a baseline for the existing wireless environment, serving as a pre‐cursor to the Phase II U‐NII‐4 testing prescribed in NPRM 16‐68, and evaluating co‐channel radio performance. In the process of conducting this testing, adjacent channel interference was also observed and recorded. Most significant of the findings was that a U‐NII‐3 Wi‐Fi access point, located as far as 100 meters away or more, and even if operated inside a building, or on an adjacent channel, caused significant interference with DSRC: This represents a consequential impact to safety given that DSRC was designed to provide situational awareness in a safety zone defined by a 300‐meter radius around a vehicle. Co‐ channel sharing with Wi‐Fi or any unlicensed radio service with similar power and duty cycle as Wi‐Fi will not be possible without a robust and reliable sharing mechanism that defers to the 30 Arnold, James A., et. al, Impairing Traffic Safety from Changes in the Safety Band: Introduction of Interference from Unlicensed Users, Pre‐ Final Version, August 2019, https://www.transportation.gov/sites/dot.gov/files/2020‐03/Rechannelization%20Inteference‐ 01AUGUST2019_FINAL_0.pdf 31 Arnold, James A., et. al, USDOT Spectrum Sharing Test Report: Effects of Unlicensed‐National Information Infrastructure‐3 (U‐NII‐3) Devices on Dedicated Short‐Range Communications (DSRC)
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Page 51 high priority safety messages. Similarly, a reallocation of channels would need to provide guard bands to protect both radio services from adjacent channel interference from the other. The report goes on to provide several additional findings related to both co‐channels sharing, and adjacent channel interference caused by Wi‐Fi that, if present, would severely impact the safety capabilities of DSRC. USDOT Analysis of FCC Phase I Sharing Report Out‐of‐Band Emissions for U‐NII Adjacent and Next Adjacent Channel In March 2020, USDOT released a Pre‐Final Version of their findings related to a deeper exploration of the test results captured by the FCC during the FCC's Phase I testing.32 With C‐V2X now part of the equation, and with the latest NPRM allocating an individual channel each for DSRC and C‐V2X, this further exploration by USDOT considers the impact to both, assuming a 10 MHz channel (Ch. 180) for DSRC, and a 20 MHz channel (Ch. 183)
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Page 52 The process included collection of baselines DSRC performance data, introducing Wi‐Fi on adjacent, overlapping channels, and comparing the results. Test results showed the potential for cross‐channel interference that would impact DSRC up to 500 meters or more, but specifically in the 200–300m range. It further demonstrated that the closer the waveform conformed to the spectral mask requirements for Wi‐Fi devices, the greater the cross‐channel interference impact was.
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Key Terms
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