Industry Associations, New York City Express Concern About Unlicensed 6 GHz Use
Wednesday, November 13, 2019 | Comments

A group of associations and companies representing public safety; first responders; railroads; electric, water and natural gas utilities; and oil and gas producers across the U.S. sent a letter to FCC Chairman Ajit Pai opposing the commission’s proposal to allow unlicensed use in 6 GHz spectrum.

The letter, signed by about 70 associations and utilities, expressed concern that allowing unlicensed use in the spectrum could cause interference that could interfere with critical mission-critical systems. Unlicensed operations in the band should only be allowed in the band if the FCC adopts more stringent interference protections for co-channel and adjacent channel microwave systems, including technology to mitigate the risk of interference by prior coordination of unlicensed operation.

“We are very concerned that the proposed mitigation scheme for protecting public-safety and CII users from interference — the automated frequency coordination (AFC) system — is theoretical in nature and has not been tested or proven,” the letter said. “Moreover, the commission’s current proposal does not contemplate a mechanism for ensuring that unlicensed users take responsibility for the cost impact of the interference resulting from unlicensed devices operating in the 6 GHz.”

The letter suggested that the FCC consider working with one or more laboratories to ensure that the untested interference mitigation measures proposed in the rulemaking will work before unlicensed operations are allowed in the band.

The letter said the 6 GHz band is uniquely suited for use for a variety of mission-critical applications including public safety and critical infrastructure industries (CII).

“There will likely be millions of unlicensed devices seeking access to the 6 GHz band, which will make protecting these public safety and CII networks from interference extremely difficult, if not impossible,” the letter said. “Therefore, it is also important that the commission adopt minimum standards for updating AFC systems and clarify that unlicensed operators or AFC system operators are legally liable for the consequences of interference to licensed microwave systems in the band.”

Such an approach is important because many CII entities have few options to relocate those system out of the 6 GHz band, the letter said. “There is no currently available spectrum for relocation out of the 6 GHz band that provides the same capabilities, and while some of the entities we represent may consider using fiber, for many of the signatories below, deploying fiber across vast geographic territories is not economically feasible. There are, on the other hand, numerous reasonable alternatives for unlicensed operations to use other bands.” Find the full letter from the associations and utilities here.

New York City also submitted a letter to the FCC that raised concerns about unlicensed 6 GHz and specifically studies submitted by companies that support unlicensed use. In supporting unlicensed use, companies including Hewlett Packard and Qualcomm submitted a LIDAR study that explored fixed service (FS) links for public safety in New York City and a multipath study. The city said that the study in New York was performed without its prior knowledge or participation.

“While we appreciate the companies’ efforts to analyze the potential interference impacts to incumbent public-safety operations in the 6 GHz band, we do not concur that the studies presented to the commission fully examined all potential interference cases or adequately characterized the potential negative impact that interference would cause to critical public-safety communications,” New York’s letter said.

The city said it was specifically concerned about how the potential influx of low-powered devices in the band would impact the ability to isolate interference, which is already a difficult task.

“We remain unconvinced that the studies’ recommendations sufficiently protect public-safety FS microwave licensees in NYC, in part due to the analysis lacking consideration of the real-world environment in which these links operate, among other concerns,” the letter said.

The city also detailed concerns about several technical elements and metrics used in the study. Like the CII entities, the city said that in order to protect critical communications in the 6 GHz band, the commission must adopt stronger interference protections before allowing unlicensed use.

“Technologies, once proven, can only be considered to mitigate the risk of interference by prior coordination of unlicensed operations,” the letter said. “Not only are the proposed mitigation schemes for protecting public-safety users from interference theoretical in nature, the technologies are unproven, untested and have not yet been built to mission-critical standards.”

Find the full New York letter here.

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