While debate continues over how unlicensed devices will affect incumbents in the 6 GHz band, a group of companies—including Apple, Facebook, Google and Qualcomm, among others—says it's the right time for the FCC to kick off a Notice of Proposed Rulemaking (NPRM).
The tech companies cite the need for more unlicensed spectrum, and the 6 GHz band’s proximity to existing operations would allow users to create wide channels that are increasingly important for things like ultra-HD video streaming, gaming and augmented/virtual reality. Earlier this year, the group presented an engineering analysis prepared by RKF Engineering Solutions that showed spectrum sharing is feasible between 6 GHz band incumbents and unlicensed devices, or what’s dubbed Radio Local Area Network (RLAN) operations.
But Fixed Services (FS) incumbents aren’t so sure, challenging the study’s conclusions and how it was done. The Fixed Wireless Communications Coalition (FWCC), AT&T Services and National Spectrum Management Association (NSMA) criticized the study and insist that the use of RLANs will cause harmful interference to 6 GHz fixed links.
Now the group of Google, et al tech companies is saying that they’re committed to protecting 6 GHz incumbent operations from harmful interference and the recent comments by these other groups show the risk of harmful interference in the real world is just very limited. Other companies in the tech group are Broadcom, Cisco Systems, Hewlett Packard Enterprise, Intel, Microsoft, Ruckus Networks and Arris.
“The bottom line is that AT&T’s, FWCC’s and NSMA’s filings are important parts of the engineering-focused dialogue that the RKF Study was intended to advance,” the tech companies said in a May 14 filing. “By demonstrating that potential interference between RLAN devices and FS is confined to only specific, rare situations, and ruling out the possibility of widespread aggregate interference to FS, the RKF Study has narrowed the appropriate technical discussion to two discrete issues, suitable for discussion within the context of a notice of proposed rulemaking that should be issued promptly.”
According to the group, the two main issues up for further discussion are:
- Under what circumstances will RLAN operation within the main beam of an FS link pose a substantial risk of harmful interference?
- What are the most appropriate mitigation measures to effectively address that risk?
On the first question, RKF showed that even in the case of main-beam RLAN operations, RLAN devices are very unlikely to cause harmful interference to microwave links by materially degrading overall link reliability, according to the group. As for the second issue, the companies have already provided a framework for interference-protection rules that would segment the 6 GHz band and allow the FCC to apply specific mitigation measures tailored to each sub-band.
Even though the RKF study is widely "misunderstood," according to the tech companies, they're willing to play ball and want to focus on how to address interference to a fixed link in the "unlikely event" that an RLAN device is located in the main beam of the microwave link.
It’s unknown when the commission will act on the 6 GHz band, but FCC Commissioner Michael O’Rielly has said he thinks the 6 GHz band and the 3.7-4.2 GHz band are closely tied together. Last month, he referenced a recent technical study that demonstrates that reallocating the 6 GHz band for unlicensed services shows such use won’t cause harmful interference to incumbents. “To the extent necessary, interference mitigation can resolve any arising problems,” he said.