Dean Bubley: The Danger of High-Power CBRS Proposals

The U.S. Citizens Broadband Radio Service (CBRS) spectrum band has been a major success since its 2020 commercial launch. Yet it now faces a serious threat from a proposed rule change backed by a few companies.

A new study has forensically examined the effects of higher-power operations and found that they could swamp lower-power users, undermining the core premise of the “innovation band” and its carefully balanced sharing framework. 

That matters because CBRS now supports more than 400,000 low- and mid-power base stations used by enterprises, local broadband providers, major carriers and other innovative network operators. It serves a wide range of applications across sectors including airports, healthcare, energy and education.

Another study released in March highlights how embedded CBRS has become in the manufacturing sector. It is a world-leading approach to commercial wireless networks coexisting with incumbent federal and defense users in the same band. Such “dynamic sharing” models are becoming ever more important, as spectrum scarcity means commercial and government users compete for limited frequency resources.

Policymakers should be protecting and replicating this sort of wireless innovation. Instead, the ecosystem is put at risk by large national wireless carriers seeking more semi-exclusive spectrum, while weakening the competition, innovation and supplier diversity that CBRS has enabled. Such a rule change could also undermine confidence in future FCC auctions if bidders fear that spectrum rights may be materially altered only a few years later.

What is being proposed?

The Valo Analytica study is a response to the FCC’s August 2024 Notice of Proposed Rulemaking (NPRM), for a review and possible refresh of the CBRS rules. The NPRM asks whether it should add “one or more classes of higher power CBSDs”. A CBSD is a CBRS base station.

Today, CBRS has two power categories, A (low) and B (medium), broadly appropriate for indoor / small site and campus / local-area outdoor use respectively. Category B radios’ power is about 50x Category A. 

This ensures that CBRS deployments have no risk of interfering with defense incumbents, and low risk of interfering with each other – especially for “protected” PAL licensees from General Access (GAA) users that make up a large proportion of the total installed-base of systems. 

The new proposed power limits are much higher and would be massively disruptive. Category C could be about 30x greater than Category B (and 1600x Category A). Category D could be another 10x more powerful still. 

These proposals reflect previous attempts by America's largest cellular providers to make CBRS more akin to a semi-exclusive macro-cellular band. Those were (appropriately) rejected as incompatible with the intended shared use and multiplicity of users in an “innovation band”. 

The Valo Analytica study’s conclusions on the impact of introducing high power into the CBRS ecosystem are pretty damning.

Three detailed case-studies highlight the risks

To illustrate the harms expected from higher power CBRS, the study analyzes three  situations where the proposals could negatively impact existing network operators:

• John Deere’s manufacturing plants
• Miami International Airport and nearby transport hubs
• Amplex Internet, a rural wireless ISP in Ohio

These specific findings can be generalized across the industry and ecosystem as a whole.

John Deere: Industrial private networks become unusable

John Deere’s deployment is exactly the sort of use-case CBRS was envisaged for: large-scale industrial connectivity across factories and logistics operations. It relies on private cellular networks for robotics, automation, computer vision and replacement of wired infrastructure. Under current rules, the system works well, with occasional but manageable interference that can be handled through careful optimization.

But under the higher-power scenarios suggested, it effectively stops working. The modelling suggests degradation of up to 1000x under interference conditions, with huge reductions in coverage and capacity from each radio, and potentially catastrophic increases in network lag (latency). 

Miami International Airport: Critical infrastructure degraded

The MIA example illustrates a possible 30% reduction in network capacity under the new proposals, even with just a single high-power CBSD in the metro Miami area.

MIA uses CBRS for surveillance, baggage handling, IoT, border protection systems and public safety connectivity. Because of existing constraints it already operates within a limited set of channels.

Higher-power CBRS would likely eliminate access to some channels entirely. For a complex, high-density environment like an airport, this is a major operational risk and could limit further expansion and additional use-cases of the band. 

Furthermore, there could be even greater impacts to other nearby transport sites considering CBRS, such as four smaller “general aviation” airports, and passenger cruise terminals on an island near downtown. 

Amplex Internet: A real-world preview of failure

Amplex highlights the damage that existing powerful networks cause today for one provider, illustrating how such disruption would multiply and expand if high power were approved for CBRS generally. Amplex operates near the Canadian border, and it already experiences interference from Canadian macro networks using similar spectrum across Lake Erie.

As a result of these limited Canadian high power operations, Amplex suffers from outages and loss of connectivity for some of its CBRS customers, even at distances as high as 200km. The Canadian radios, which operate at similar power levels to the proposed CBRS Category C and D, implies that outages and connectivity interruptions would compound if similar high-power operations were approved widely in the United States for CBRS.

Ecosystem-wide risks, and secondary downstream effects

The report also describes system-wide degradation of capacity and usability of the band. Enterprise networks, WISPs, indoor mobile coverage systems (called neutral hosts), and temporary or “pop-up” CBRS networks for events and broadcasting would be adversely impacted.

Allowing much higher-power use of CBRS spectrum would undermine the democratic nature of CBRS and diminish the opportunity for many US innovators, including smaller domestic equipment manufacturers. Such specialists can sell to enterprises and local WISPs, even if they are frozen out of contracts with larger telecom operators, which prefer huge international vendors.

CBRS has quietly enabled a more diverse and competitive supplier ecosystem. Such diversity is unlikely to survive a shift to a macro-style regime.

Conclusions

The Valo analysis exposes the critical impacts of the proposed higher-power options on US industry and broadband service provision, with detailed illustrations and calculations of the severe effects. 

It highlights a fundamental policy choice.

CBRS can either remain a platform for:

• Local innovation and broadband provision
• Competition, industrial efficiency and transformation of key economic sectors 
• Diverse operators and suppliers 

Or it can be reshaped into: 

• Yet another macro-cell spectrum band dominated by a small number of national players for generic wireless capacity...
• …creating uncertainty and disruption for forthcoming spectrum auctions

The two models are not compatible. Allowing high-power operation is not a minor tweak to the rules. It is a redefinition of the band’s purpose, which risks undoing one of the most successful spectrum-policy experiments of the last decade.

Dean Bubbly is the Founder of Disruptive Analysis. He is one of the conveners of the 6G Reset initiative and a leading analyst covering 5G, 6G, Wi-Fi, telco business models & regulation, the future of voice/video, and the emergence of technologies such as quantum networking and AI. The study was conducted by Valo Analytica on behalf of Spectrum for the Future. The author of this article is also an advisor to SFTF. 

Broadband Breakfast accepts commentary from informed observers of the broadband scene. Please send pieces to commentary@breakfast.media. The views expressed in Expert Opinion pieces do not necessarily reflect the views of Broadband Breakfast and Breakfast Media LLC.