As the deadline for comments on the FCC’s midband spectrum consultation came, the US debate about these important airwaves heated up. An unprecedented variety of stakeholders and would-be operators is eyeing spectrum between 3.5 GHz and 6 GHz, but with very different agendas.
The regulator aims to get better use out of a portion of the C Band spectrum from 3.7 GHz to 4.2 GHz. Some players want a similar shared structure to the three-tiered CBRS scheme, proposed for the nearby 3.5 GHz band, to be expanded up to 4.2 GHz. This protects federal incumbents while supporting a licensed, priority access layer and an unlicensed, general access approach.
Others are opposed to the whole idea of opening the 3.7-4.2 GHz band for mobile broadband. The incumbent satellite community is against this, and only Intelsat has made slightly encouraging noises about being able to clear their use of it over time, given some compensation, for the good of all.
In a joint proposal, Intelsat and Intel are suggesting that the FCC allow co-primary terrestrial mobile operations in the 3.7-4.2 GHz band through commercial arrangements between MNOs and relevant fixed satellite service (FSS) operators. The latter group would work cooperatively to identify areas of the country where they could undertake the “complicated and costly” process of clearing portions of the band for terrestrial use.
The FCC has pointed out that the users of this spectrum have been slowly evaporating over time, falling from 39,000 licenses in 1988 to under 13,000 by 1997 and still falling. However, comments to the press over the course of the week, put Intelsat in the role of a traitor to the satellite cause, reminding the FCC just how many ground stations and antennas were active in this segment.
The Notice of Inquiry from the FCC was issued in July, but comments are only published once the deadline for reply has passed. The FCC asked about three key areas of spectrum, from 3.7 GHz up to 24 GHz, isolating the 500 MHz from 3.7 GHz to 4.2GHz, which is used by satellite operators, some for broadband delivery, some from uplink to satellites.
The Notice also calls out the 500 MHz from 5.925 GHz to 6.425 GHz which is essentially paired with the 3.7 GHz to 4.2 GHz for satellite purposes (Earth to Space), as well as the 6.425 GHz up to 7.125 GHz, which are also under existing use for governmental radars.
The FCC reminded us all that it has been already active above the 24 GHz line, making 11 GHz available licensed and unlicensed for fixed and mobile use, as well as finding 18 GHz, above 95 GHz, for commercial use.
WiFi community battles for unlicensed expansion in 6 GHz:
There was also rising pressure for more unlicensed spectrum. About 30 companies signed a filing which claimed that Part 15 (unlicensed) access is essential in the 6 GHz (5925-7125 MHz) band to meet demand for next generation wireless broadband services. Signatories included Apple, Cisco, Google, Facebook, Broadcom, Intel, Qualcomm and Hewlett-Packard Enterprise.
They propose that the FCC should establish four 6 GHz sub-bands, with different technical rules and interference protections in each one, depending on the nature of the incumbents in the frequencies.
The four sub-bands proposed are:
U-NII-5: 5925-6425 MHz
U-NII-6: 6425-6525 MHz
U-NII-7: 6525-6875 MHz
U-NII-8: 6875-7125 MHz
The IEEE, which governs the 802.11 standards that underpin WiFi, recently voted to extend coverage to the 6 GHz band. As this spectrum adjoins the 5 GHz unlicensed band, that would support wide, gigabit-capable channels, as standardized in the upcoming 802.11ax specifications, which aim to boost WiFi data rates in dense environments.
Christopher Szymanski, director of product marketing and government affairs at Broadcom, commented in the filing: “We’re under a spectrum crunch.” He argued that, although about 80% of smartphone traffic goes over WiFi, there has been no corresponding increase in the spectrum devoted to the technology. “We think it’s very important that the Commission move quickly. We’re not looking to displace, we’re looking to protect,” he added.
While not among the signatories, the WiFi Alliance has been making similar protestations. It claims that a recent decision by the US NTIA, foreclosing unlicensed operations in the 5.35-5.47 GHz (U-NII-2B) band, significantly disrupted WiFi industry plans to support growing demand in midband spectrum.
Of course, some MNOs want at least some of the 6 GHz band for licensed use. T-Mobile USA wrote that it “urges the Commission to consider making some or all of this band available for licensed mobile broadband use.” Ericsson added that the 6.425-7.125 GHz band would be a good complement to millimeter wave spectrum for licensed mobile use cases in densely populated areas, and for connected car applications.
By contrast Verizon, which holds microwave spectrum in the band, said the proximity of 6 GHz to the 5.15-5.35 GHz and 5.47-5.727 GHz bands makes it attractive for unlicensed use, and therefore the telco conditionally supports unlicensed use as long as there are rules that provide adequate protections to incumbents and future microwave deployments.
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