Pai Puts Forth 5.9 GHz Proposal


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FCC Chairman Ajit Pai has chosen a path forward for the beleaguered 5.9 GHz band. In 1999, the agency allocated 75 MHz of spectrum in the 5.9 GHz band for Dedicated Short-Range Communications (DSRC), which is a form of automotive safety and communications. But DSRC is not widely deployed, and looks to be overshadowed by the newer Cellular Vehicle to Everything, or C-V2X technology.  

Pai shared with his colleagues Wednesday a proposal to make available the lower 45 MHz of the band for unlicensed uses like WiFi and allocate the upper 20 MHz for a new automotive communications technology, Cellular Vehicle to Everything, or C-V2X. C-V2X uses cellular protocols to provide direct communications between vehicles, and, as the name suggests, everything—including other vehicles on the road, infrastructure (like light poles), cyclists, pedestrians, and road workers. 

C-V2X is also expected to support new, advanced applications as the nation transitions to faster, more responsive 5G networks. Automakers like Ford, Audi, BMW, Daimler, and Tesla support C-V2X. “Our hope is that this move will unlock new vehicle safety services, using less spectrum and on a much faster timeline than we have seen or realistically could see with a DSRC-focused policy,” said Pai in a speech on Wednesday.  

The agency is moving towards mixed and/or shared spectrum use in general as the need for wireless spectrum explodes. WiFi now carries more than half of the internet’s traffic, according to the agency. “It has arguably kept cellular networks afloat by reducing the traffic load on those networks,” Pai said.

But its popularity means the FCC needs to allocate more spectrum for unlicensed use. He pointed out his plan is a departure from the Commission’s recent exploration of allowing unlicensed devices to share the same spectrum with DSRC. Preliminary testing of a sharing regime showed some promise, according to Pai, but further testing would be needed to carry out a complex sharing regime, “and more testing would mean this valuable spectrum would likely lie fallow for several years.”

However DSRC isn’t dead. Japan, for example, has a single 10-megahertz channel for DSRC that is used for collision avoidance around intersections. So he’s proposing the agency seek public input on whether to allocate the remaining 10 MHz of spectrum in the 5.9 GHz band for DSRC or C-V2X. 

He proposes to dedicate 45 MHz exclusively for unlicensed operations, and establish a home exclusively for transportation-related communications. That’s why he’s also proposing dedicating 30 MHz of spectrum in the 5.9 GHz band for Intelligent Transportation Systems.

The Chairman intended to move on the 5.9 GHz proposal earlier, but the Department of Transportation voiced concerns. Specifically, the DOT opposed allocating the entire band to unlicensed WiFi; the DOT also wanted all 75MHz reserved for transportation safety, FCC officials told reporters. After months of “substantial” discussions, the result is a compromise that resulted in “meaningful changes” to the item, said one Commission official.   

Pai wants the Commission to vote on the Notice of Proposed Rulemaking at the December 12 meeting.

November 21, 2019             

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