Wireless Industry Opposes Tighter Emissions Limits for High Band Operations
Future rules for the 37 GHz band must protect licensed wireless operations in the upper 37 and 39 GHz bands and shouldn’t impose new emissions limits, CTIA said in comments on a Further NPRM aimed at spurring greater use of the spectrum. FCC commissioners approved an order and FNPRM on the band in April and comments were due Monday in docket 24-243. The National Academy of Sciences’ Committee on Radio Frequencies (CORF) repeated its concerns (see 2409300028) about protecting the 36-37 GHz earth exploration satellite service (EESS) band, which is critical for science, it said.
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The FNPRM asks whether emission limits for the 37-40 GHz spectrum are sufficient to protect passive observations below 37 GHz. NTIA late last year released the first of the band-specific reports called for in the Biden administration’s national spectrum strategy (see 2403120056), focusing on the 37 GHz band. The report was developed with DOD and recommended a federal and nonfederal co-primary sharing framework for the lower 37 GHz band (see 2412030057).
There are “extensive wireless deployments” in the upper 37 and 39 GHz bands as a result of the commission’s 2020 spectrum frontiers auction, CTIA said. “The few proponents of more stringent emission limits have not presented any technical basis for imposing additional restrictions on these licensed operations,” the group said. “No party, including NTIA, has presented new characteristics or analysis that is inconsistent with the established technical foundation underlying the Commission’s 2016 Spectrum Frontiers Order,” CTIA added.
While CORF argued last year that out-of-band emission (OOBE) limits are “barely sufficient” to offer protection from a single transmitter in the lower 37 GHz band, the committee's “assessment is limited to a simple, static analysis, and it does not consider the complex deployment and operational characteristics of terrestrial broadband systems or other systems involved,” CTIA argued. CORF’s assessment doesn’t “demonstrate the need for a change, or otherwise undermine, the Commission’s assessment in 2016.”
CORF noted in its comments on the FNPRM that the 36-37 GHz EESS (passive) band “is one of the key passive remote sensing bands across the microwave and millimeter wave spectrum that enable spaceborne sensors to analyze the state of Earth’s atmosphere and surface.” The band is “essential because it provides unmatched radiometric sensitivity to key Earth system variables, including precipitation and cloud liquid water; surface freeze-thaw conditions and snow cover; and sea-ice concentration and ocean vector winds.”
The FCC should adopt appropriate rules “before extensive deployments occur," CORF said. While lower 37 GHz commercial deployments “having only occurred thus far under experimental licensing, already some commenters in this proceeding have argued that adopting new rules would impose an onerous cost to refit existing equipment,” the committee said.
“Not only have the existing technical rules proven sufficient to protect passive sensors below 37 GHz, but also changing the rules for already-auctioned, licensed, and deployed spectrum would cause significant disruption in the Upper 37 GHz and 39 GHz ecosystems,” AT&T commented. If the commission adopts the more stringent OOBE limits, “it would contravene the investment-backed expectations of … licensees, who bid on their licenses at auction in good faith reliance on the existing Part 30 rules,” the carrier added.
Ericsson urged the FCC to leave the rules intact. “A more restrictive limit is unnecessary, would inhibit the deployment of dual-use technology in the Lower 37 GHz Band, and would degrade performance for existing licensees in the 37.6-40.0 GHz band,” Ericsson said. When the FCC determined the appropriate OOBE limit for the lower 37 GHz Band in 2016, it took into account passive sensors in the 36-37 GHz band, “and there is no sound basis to revisit that limit,” the company said.
Qualcomm also defended current emissions limits. “Should the FCC modify the OOBE level as requested by federal interests, it must maintain the portion of the rule allowing -5 dBm/MHz within the first 10 percent of the channel bandwidth outside the licensee’s frequency block,” Qualcomm said. If that allowance is removed, the company said its calculations show that mobile devices operating in the lower 37 GHz band “will have to lower their in-band power by 3 to 5 dB for transmission waveforms that support operations at the cell edge, reducing band coverage and directly impacting an important mobile system performance metric.”