[co-author: Ambia Harper]
For twenty years, the 5.9 GHz band (5.850-5.925 GHz) has been dedicated to intelligent transportation systems and vehicle safety, and in particular a technology called Dedicated Short Range Communications (DSRC). On November 18, 2020, the Federal Communications Commission (FCC) unanimously approved a First Report and Order reallocating a majority of the 5.9 GHz band away from connected vehicle technologies. The Commission repurposed the lower 45 megahertz at 5.850-5.895 GHz for unlicensed commercial uses such as Wi-Fi. The upper 30 megahertz of spectrum in the 5.895-5.925 GHz band is still designated for intelligent transportation systems, but the Commission has endorsed a new standard for automotive uses, C-V2X. Existing automotive licensees operating in the part of the band now designated for unlicensed use will have one year to transition operations to the 5.895-5.925 band. The FCC has not yet set a timeline for licensees to transition from DSRC to C-V2X.
Allowing unlicensed use in the 5.9 GHz band
The Commission decided to allocate the lower 45 megahertz of spectrum for Wi-Fi and other unlicensed uses, despite unified opposition from automobile manufacturers, the U.S. Department of Transportation, state departments of transportation, some law enforcement groups, and the broader transportation safety industry. The Commission was motivated by the increasing and insatiable demand for Wi-Fi and synergies between the existing (U-NII-3) 5 GHz Wi-Fi band that will allow the creation of high-throughput channels of up to 160 megahertz that will be able to support gigabit Wi-Fi connectivity.
The FCC preserved the upper 30 megahertz of spectrum for transportation safety. In evaluating how to optimize the use of the safety spectrum, the FCC concluded that DSRC had exhausted its window of opportunity, that C-V2X technologies show greater promise, and that 30 megahertz in the 5.9 GHz band was sufficient for transportation safety operations when considered in concert with other automotive safety technology (such as vehicle radar) being deployed in other spectrum.
Transition to C-V2X
Last year, in the 5.9 GHz Notice of Proposed Rulemaking, the FCC sought comment on whether it should assign all thirty megahertz of transportation safety spectrum to C-V2X or reserve the 5.915-5.925 GHz band for DSRC. After reviewing the record, the Commission decided to dedicate the spectrum solely to C-V2X. The FCC noted the failure of DSRC to take hold in the industry, citing the limited number of operational projects, roadside deployments, and vehicles equipped with DSRC technology. In addition, because DSRC and C-V2X are technically incompatible, the FCC concluded that using a single technology would maximize efficient use of the spectrum and the safety benefits of the technology. The FCC also noted other benefits of C-V2X, including global momentum toward adoption of C-V2X, its ability to achieve greater network effects and leverage cellular networks, its compatibility with 5G, and current deployment of the technology by many auto manufacturers and U.S. states.
Impact on existing DSRC licensees
The FCC also approved an Order of Proposed Modification, modifying all licenses for automotive safety operating in the 5.9 GHz band to allow only for operation in the 5.895-5.925 GHz portion of the band. Licensees must retune their equipment to access only the upper thirty megahertz of the band or replace their equipment with transmitters designed to use only the revised band parameters. The Commission has given licensees one year from the effective date of the First Report and Order to transition out of the lower portion of the band.
Procedures to implement the full transition from DSRC to C-V2X have not yet been developed. The FCC adopted a Further Notice of Proposed Rulemaking (FNPRM) to generate a more complete record on which to base its decision. In the FNPRM, the Commission seeks comment on the appropriate timeline for the transition, procedures necessary to ensure a smooth transition to C-V2X, technical parameters, and other transition considerations, as well as other matters related to the unlicensed portion of the band.
The effective date of the First Report and Order and the comment period for the FNPRM will be determined after publication of the decision in the Federal Register.