In line with a general policy of allowing more flexible use of radio frequency spectrum, the Federal Communications Commission’s (FCC) posted a proposed rule on February 6 that would reallocate some of the spectrum that has, since 1999, been reserved for transportation communications. The move has pitted two federal agencies against each other, with U.S. DOT arguing against reallocating spectrum.

After the 1998 Intelligent Transportation Systems Act, the FCC reserved 75 MHz of the 5.9 GHz band (the distance between the frequencies of 5.850 GHz and 5.925 Ghz) for digital short range communications (DSRC). Although the allocation was officially adopted in 1999, it took until 2008 to adopt full rules and negotiate spectrum-sharing agreements to allow transportation DSRC use. Since then, multiple pilots, demonstrations, and limited deployments have been implemented. But wide-scale adoption of DSRC is still years away, as benefit accrue only after widespread equipage of both vehicles and infrastructure.

For several reasons, listed below, the FCC wants to break up the 5.9 GHz band. The proposed rule would designate the lower 45 MHz (5.850-5.950) to unlicensed Wi-Fi and broadband. The remaining 30 MHz would to be dedicated to intelligent transportation systems (ITS) (5.950-6.25), with the upper 20 MHz given exclusive access to “cellular vehicle-to-everything” (C-V2X) (5G). On December 12, the FCC sought comments on whether to retain the remaining 10 MHz (5.950-6.050) for DSRC or to dedicate it to C-V2X. The new proposed rule would allow C-V2X and/or DSRC devices at 5.895-5.905 GHz (see figure).

Three primary issues are driving the FCC’s decision, according the NPRM. First, FCC believes that by allocating the lower 45 MHz to unlicensed uses, it could be combined with the adjacent unlicensed band to create a larger continuous block. This would deliver more capacity and “advanced features” for Wi-Fi users. The NPRM also cites the fact that cellular C-V2X is not allowed on the band currently, and that technology is advancing much more rapidly than DSRC in some applications. The NPRM repeats the calls for commons on whether cellular C-V2X and DSRC can exist on the upper band.

The transportation industry is nearly unanimous in its opposition to the proposed rule, including U.S. DOT. The department released a technical paper outlining the risks with taking away the band, which has been amplified by ITS America, the Auto Alliance and other industry groups. While some support opening the band for cellular C-V2X, they maintain that the entire 75 MHz band should be reserved for transportation applications. Eno, too, has recommended keeping the spectrum for transportation uses.

Much of the opposition is couched in safety and the potential to reduce crashes. And while the scale of the lifesaving capabilities are probably unrealistic in the real world (at least in the medium term) new technologies will likely be able to save lives and improve operations. Opponents say, among other things, the band will risk interference from other uses in the narrow band, meaning that safety applications will not function properly. Also, the U.S. DOT study expresses doubt that 5G and DSRC can share the same band without interference. Once spectrum is allocated to other uses, it will be nearly impossible to reclaim it.

The comment period is open until March 9, and the FCC asks, “whether alternate spectrum band approaches would better achieve the goal of maximizing the effective and efficient use of the 5.9 GHz band, including whether differently sized sub-bands or greater flexibility to introduce additional vehicular safety communications technologies into the band would be warranted.” Given the stakes are high, and this is a strange case where one part of the Administration is fighting another, expect lots of comments.