AT&T Proposes Significant Adjustments for CBRS and 3 GHz Band
AT&T on Wednesday called for major changes in how 3 GHz, including the citizens broadband radio service band, is configured, going beyond what the FCC proposed in an August NPRM (see 2408160031). Meanwhile, during a Broadband Breakfast webinar Wednesday, experts said the CBRS band has demonstrated the value and importance of spectrum sharing.
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Under AT&T’s proposal, presented in Rhonda Johnson's blog post, the CBRS allocation at 3.55-3.7 GHz would expand and relocate to 3.1-3.3 GHz, increasing the amount of available spectrum from 150 to 200 MHz. Johnson is the company's executive vice president-federal regulatory relations.
Allocations in the 3.45 GHz band and C band, 3.7-3.98 GHz, which were sold to carriers in FCC auctions, wouldn’t change. The former CBRS band would be auctioned for licensed, full-power use. The FCC adopted initial rules in 2015, creating a three-tier model for sharing the 3.5 GHz spectrum, while protecting naval radars. The agency auctioned priority access licenses (PALs) four years ago (see 2008260055).
“Today, 3 GHz spectrum is powering 5G networks worldwide and the CBRS band now resides between two crucial, high-power, licensed 5G bands -- the auction of which raised more than $100 billion combined for the U.S. Treasury,” Johnson wrote: “It is wise for the Commission to revisit the CBRS band to increase its utility, particularly given … significant changes in the spectrum environment. However, the changes the Commission proposes to make would still hold this band back from reaching its full potential.”
Wi-Fi advocates were still studying the AT&T proposal Wednesday, but early reviews were negative.
“AT&T’s proposal is a red herring premised on wishing away the U.S. Navy’s need to continue using CBRS spectrum,” Michael Calabrese, director of the Wireless Future Program, told us. “Clearing military radar off an additional 150 MHz of spectrum in 3 GHz is the gating question and highly unlikely,” he said: “The FCC adopted low-power and database-coordinated sharing of CBRS to work around the fact that the Navy relies on those frequencies for national security.”
CBRS provides local spectrum access to “a wide variety” of businesses, schools, rural wireless ISPs and other operators “while protecting incumbent U.S. Navy systems,” Calabrese said. “After just four years, more than 1,000 operators have deployed more than 400,000 access points to provide service on CBRS spectrum, which is roughly equal to the total number of cellsites in use by U.S. mobile carriers nationwide after 30 years of deployment.”
“AT&T doesn’t just want to kill competition in the CBRS band, they want exclusive control over spectrum currently shared among a diverse array of users,” Spectrum for the Future said. Four years ago, it said, “AT&T declined to participate in the CBRS auction alongside the other two major U.S. cellular carriers, and now the company is feeling left out of the private wireless boom and desperate to arrest the new competition driving down prices for U.S. consumers.”
AT&T’s proposal, an NCTA spokesperson emailed, “should be seen for what it is -- a desperate attempt to thwart competition and punish the many businesses, communities, and consumers who made good-faith investments in reliance on the FCC’s innovative CBRS framework.”
Understanding Sharing
Researchers are still working on understanding the dynamics of sharing spectrum, Monisha Ghosh, professor of electrical engineering at the University of Notre Dame, said during the webinar. The school’s football stadium in South Bend, Indiana, has 862 standard-power 6 GHz access points “deployed and working,” Ghosh noted. Her students take measurements when the stadium is full during games.
The CBRS band has been key to democratizing access to spectrum, said Ghosh, also former FCC chief technologist. In South Bend, during the COVID-19 pandemic, the city and school district reached underserved residents using CBRS, she said. “This is exactly the kind of thing that CBRS, which was labeled the innovation band, was supposed to do, and it’s doing that beautifully.”
Some 400,000 CBRS base stations or access points are currently using at least one channel, Ghosh said. “This is incredible if you think about [the fact that] there were zero four years ago,” she said. “The growth in CBRS has been phenomenal,” but issues remain.
Many deployments in the general authorized access tier of CBRS have largely taken a 4G or 5G system “and just plunked it into this band without realizing that now you’re operating in a shared spectrum environment,” Ghosh said. Devices have to be designed for sharing at the radio and protocol level, she said. “GAA users are left to … figure out how to coordinate, and it’s going not so well -- that could be improved.”
The national spectrum strategy is well underway and unlicensed advocates are making the case that sharing is a “better choice” in many bands than clearing for licensed use, said Mary Brown, executive director of WifiForward. Brown noted that because unlicensed spectrum lacks “an auction value,” you have to “go behind what unlicensed spectrum delivers in the economy and take a look from an economic value point of view about what it’s delivering.”
Dean Bubley, technology analyst and founder of the U.K.’s Disruptive Analysis, said he has long focused on democratizing how spectrum is used. The spectrum needs a user has depends on the “importance and criticality” of the use case, he said. If you’re a mining company operating 400-ton autonomous vehicles, “you obviously have a fairly high level of safety-critical requirements in a place that almost certainly is not going to have public network coverage.” However, if you’re operating payment terminals at a festival, “it’s an annoyance, but it’s not a life-safety issue if the network is unavailable.”
Every country should develop a national spectrum strategy, Bubley argued. The U.S. should “take its leadership role in evangelizing the idea of spectrum sharing and take it around the world,” he said. “This is the way to essentially improve wireless for all of humanity.”