In mid-August, the Federal Communications Commission succeeded in its long-held plan to reallocate a portion of the spectrum from car-to-car and car-to-infrastructure communication (known as V2X) to Wi-Fi instead. However, the FCC didn't reassign that entire region of bandwidth—30 MHz remains set aside for "intelligent transportation systems." And the FCC should grant automakers a waiver to allow them to start deploying cellular-based V2X (C-V2X) safety systems, said the National Transportation Safety Board in a letter it sent the FCC on Monday.

The saga of V2X is a long-running one. The FCC originally saved the spectrum around 5.9 GHz for use with V2X in 1999, but despite keen interest from some automakers and industry groups like the American Association of State Highway and Transportation Officials (AASHTO) and the Intelligent Transportation Society of America (ITS America), the technology still has not been deployed.

Seeing that failure, the FCC decided in 2020 to reallocate some of the bandwidth to Wi-Fi, leaving the frequencies between 5.895 and 5.925 GHz for V2X. ITS America and AASHTO sued the FCC to prevent this, but the US Court of Appeals for the District of Columbia ruled in favor of the FCC in August, allowing the commission to go through with its plan.

NTSB says C-V2X is A-OK

This has dismayed the NTSB, which has written to the FCC as part of the commission's public comment period as it considers a waiver requested by automakers to deploy C-V2X technology. Conceptually, C-V2X works the same as the older V2X—direct vehicle-to-vehicle or vehicle-to-infrastructure communication but using cellular radio protocols instead of the dedicated short-range radio communication protocol.

The FCC should grant this waiver, said the NTSB, which notes in its letter that it has recommended that the nation adopt wireless-based collision-avoidance technology since 1995. Connected vehicle technology would reduce the ever-escalating carnage on US roads, said the NTSB, and the agency also urged the FCC to make sure that Wi-Fi devices don't encroach on the remaining 30 MHz of intelligent transportation system frequencies.

"30 MHz is enough for basic safety features," said Balázs Tóth-Pintér, a communications specialist with V2X company Commsignia, who pointed out that the EU has only allocated a total of 40 MHz for V2X. And unlike in the US, deployment is happening in Europe. "This year, we'll see approximately 1 million V2X cars in Europe. The expected penetration will be in the 10 million-ish range by around 2024–2025," he told Ars.

Tóth-Pintér also noted that the court's decision only added clarity to the field and that Commsignia has "been working on that 30 MHz since the FCC made its decision almost two years ago. We deliver equipment with both DSRC and C-V2X included, so changing the physical network layer is not a big issue. Now we can go full speed ahead with deployments," he said.