Will the FCC raise CBRS power levels?

Some 5G providers want the FCC to issue new rules for the 3.5GHz CBRS spectrum band that would raise broadcast power levels closer to those in the nearby C-band and 3.45GHz bands.

Mike Dano, Editorial Director, 5G & Mobile Strategies

June 17, 2024

7 Min Read
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The FCC's chairwoman said she's going to consider additional changes to the 3.5GHz CBRS spectrum band. But it's not clear whether increasing CBRS power levels is on the agenda.

The issue is important to big wireless network operators like Verizon and Dish Network. That's because transmissions in the CBRS spectrum band today are capped at levels that are lower than those in nearby bands like C-band and 3.45GHz. Those bands, unlike CBRS, are currently used for broad, high-power 5G operations in part because they support higher broadcast power levels.

"We can preserve and enhance the Citizens Broadband Radio Service [CBRS] to both protect progress and look ahead to further opportunities," said FCC Chairwoman Jessica Rosenworcel in a statement late last week. "This proposal represents our continued commitment to developing, and improving, spectrum sharing models that provide opportunity for expanded use of the airwaves."

Specifically, Rosenworcel said she would consider "whether to align 3.5GHz protection methodologies with those in adjacent bands, revisit our Environmental Sensing Capability (ESC) approval procedures, and facilitate the continued introduction of Citizens Broadband Radio Service in areas outside of the contiguous United States."

But the details of Rosenworcel's proposals are now "on circulation." In FCC parlance, that means each of the five commissioners on the FCC will privately review and deliberate possible rule changes to the CBRS band. Then, if the agency arrives at some kind of consensus, Rosenworcel might make a more formal, public proposal that the full agency would vote on during one of its monthly meetings.

There's no guarantee that items "on circulation" will eventually mature into more formal rules. After all, there are more than a dozen items "on circulation" at the FCC, including a few that are more than a year old.

CBRS on steroids

The CBRS band is generally considered unsuitable for high-speed 5G operations across wide geographic operations. That's because FCC rules on transmissions in the band limit the power level providers can use to broadcast their signals.

That's noteworthy for Verizon. As Light Reading reported in 2019, Verizon has been adding support for the 3.5GHz CBRS spectrum band to its network for years. And in 2020 the operator spent $1.9 billion to purchase CBRS spectrum licenses across the country in an FCC auction.

But 2021 tests by RootMetrics showed the limits of Verizon's CBRS efforts. The firm found that Verizon's CBRS spectrum helped to double the speeds available on its 4G LTE network in Philadelphia. However, RootMetrics noted that Verizon's CBRS coverage in Philadelphia was not extensive.

Similarly, OpenSignal reported in 2021 that the CBRS band can boost over network download speeds, but "lower power levels dramatically affect users' experience if they are not close to a cell tower."

As a result, according to 2023 findings from trade association CTIA, CBRS-powered wireless signals are relatively scarce compared with wireless signals in spectrum like the C-band. 

"C-band is delivering significantly more value for consumers, consistent with the fact that operators were willing to pay nearly 18 times more for C-band spectrum compared to CBRS licenses at auction," CTIA wrote last year, citing the $81 billion in bids generated by the FCC's C-band spectrum auction in 2021.

Thus, some players in the industry have been asking the FCC to raise the power limits in the CBRS band to make them similar to the C-band (which sits just above the CBRS band) and the 3.45GHz band (which sits just below it).

"Rationalizing the CBRS power levels with adjacent bands will provide carriers and consumers enormous benefits by enabling more efficient use of the spectrum and lowering the costs of deployment," EchoStar's Dish Network wrote recently.

AT&T, for its part, petitioned for higher CBRS power limits as far back as 2019.

The pushback

But for other CBRS proponents, the FCC's current lower power levels are just fine.

According to one industry executive who declined to be named, higher CBRS power levels could impact the use of CBRS spectrum in indoor and private wireless deployments. That's because increased power levels could create coordination difficulties between CBRS networks operated inside venues and CBRS networks operated outside by big, public wireless network operators.

Thus, CBRS rule changes could have a significant impact on the nascent but burgeoning markets developing around private wireless network installations and neutral host indoor networks for smaller venues.

The US government's Commerce Spectrum Management Advisory Committee (CSMAC) recently presented its CBRS recommendations to the NTIA, which advises the White House on telecom issues. In its report, the committee highlighted some wireless industry concerns about higher CBRS power limits.

"Two new-entrant MVNO operators and their industry association and some private wireless network operators ... did not see a need for higher transmit power limits for their use cases and noted that allowing higher transmit power would increase the risk for interference amongst CBRS users," according to the report, which was published at the end of 2023.

The identities of the two "new-entrant MVNO operators" were not disclosed, but they're likely Comcast and Charter Communications. Both cable companies purchased CBRS spectrum and are hoping to build small-scale CBRS 5G networks in support of their MVNO efforts.

The technical details

Power levels are just one of many CBRS issues that might be addressed by the FCC. Another, related issue involves the timing synchronization among CBRS users and users in other bands.

According to one executive familiar with the issue, Time Division Duplex (TDD) technology is used across C-band, CBRS and 3.45GHz. But there is no TDD timing synchronization requirement for transmissions in the CBRS band. That could potentially create interference issues between CBRS users and users in nearby bands if they're not all subject to the same timing synchronization requirements.

Others are concerned too. 

"If you're planning to deploy a CBRS network, it's vital to acknowledge the challenges of network synchronization," wrote CBRS equipment vendor Ericsson late last year. "By ensuring that your network is synchronized to within 3 µs of other CBRS networks in the area, you can help ensure that your network operates reliably and efficiently without interfering with other networks."

Indeed, timing continues to represent a challenge across wide sectors of the telecom market. Dish, for example, recently explained the challenges it faced in implementing timing requirements across its 5G cloud network deployment.

The bigger debate

Rosenworcel's CBRS explorations come just weeks after the FCC announced new rules to expand unencumbered services in the band to an additional 72 million people.

Specifically, the agency said it would shrink the Dynamic Protection Area (DPA) neighborhoods along coastlines and around federal facilities throughout the country. DPAs are areas where federal users such as the US Navy can boot commercial users out of part of the CBRS band. 

By reducing the size of CBRS DPAs, the FCC managed to increase the amount of territory where CBRS users wouldn't have to worry about US Navy operations.

Reducing the size of DPA areas was one of several recommendations in the CSMAC's recent report to the NTIA. The report did not recommend increasing CBRS power limits, but it did recommend studying the topic.

More broadly though, the FCC's CBRS efforts arrive amid an ongoing debate in Washington, DC, over the future of spectrum sharing across the US. The CBRS band is noteworthy in that it's actively shared between federal and commercial users.

A group of lobbyists – fronted in part by some of the country's biggest cable companies – are urging regulators to pursue expanded spectrum sharing technologies in more spectrum bands. Meanwhile, the 5G industry has generally argued against spectrum sharing in favor of high-power, exclusive-use spectrum licensing regimes.

About the Author(s)

Mike Dano

Editorial Director, 5G & Mobile Strategies, Light Reading

Mike Dano is Light Reading's Editorial Director, 5G & Mobile Strategies. Mike can be reached at [email protected], @mikeddano or on LinkedIn.

Based in Denver, Mike has covered the wireless industry as a journalist for almost two decades, first at RCR Wireless News and then at FierceWireless and recalls once writing a story about the transition from black and white to color screens on cell phones.

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