February 3, 2017–NCTA, Qualcomm, Inc., and Broadcom Ltd. today submitted a technical submission to the FCC that they say validates a proposal to rechannelize the 5.9 gigahertz band to enable sharing between dedicated short-range communications (DSRC) and Wi-Fi applications. They also blasted automaker support of an alternative detect-and-avoid sharing mechanism as a “prevent-defense strategy that slowed the previous Commission.”
“In developing the rechannelization proposal, we have adopted a practical approach. All of our companies are fully committed to not causing harmful interference to latency-sensitive, safety-critical services, and we stand ready to continue applying our technical resources and expertise to ensuring that rechannelization succeeds,” the filing in ET docket 13-49 said. “We therefore welcome the opportunity to address automakers’ questions and concerns, some of which appear to rest on misunderstandings of the rechannelization approach, and to work with the Commission to resolve any issues it identifies in the testing process.
“The automakers are asking the Commission to retain the existing DSRC band plan and make no changes to the DSRC rules, but this is neither a viable solution for Wi-Fi nor a sound long-term strategy for DSRC,” today’s filing argued. “The rechannelization approach, on the other hand, would give DSRC exclusive access to the 30 MHz at the upper end of the band for latency sensitive, safety-critical services. This approach also includes a well-developed sharing mechanism in the lower 45 MHz portion of the band that allows for both Wi-Fi and DSRC operations in those channels.
“But unlike detect-and-vacate, rechannelization would allow efficiency-enhancing sharing without requiring all Wi-Fi users to unnecessarily vacate the entire band for long periods of time whenever an access point detects a DSRC signal — even where DSRC is used for commercial purposes — as the automakers’ approach requires. This aspect of the automakers’ detect and vacate approach, as currently contemplated, would make the proposed U-NII-4 band effectively unusable for Wi-Fi,” the filing contended. “The automakers go so far as to argue that the FCC should apply this unworkable sharing approach to the upper portion of the current U-NII-3 band, presumably with the hope that the Commission will recall millions of consumer Wi-Fi devices already in the market or block the use of future devices. This is not a viable sharing approach.”
The filing discussed “rechannelization’s impact on co-channel, adjacent-channel, and DSRC-to-DSRC interference” and concluded that rechannelization would provide the best interference protection for safety DSRC communications. —Paul Kirby, firstname.lastname@example.org