‘There are not a lot of easy bands left’ says NTIA senior advisor
With both mmWave and midband 5G auctions concluded and development and/or deployment underway for existing spectrum releases, one of the biggest spectrum question now is: What’s next?
Conversations on spectrum policy are shifting focus to renewing the pipeline of airwaves under consideration for future use, both for 5G and as-yet-unstandardized 6G systems. Federal agencies are also reconsidering their roles and relationships in shaping that pipeline, and where innovation or spectrum sharing may help to bolster commercial spectrum access while not interfering with the ability of agencies as diverse as NASA, the Department of Defense, the Federal Aviation Administration and the National Oceanic and Atmospheric Administration to do their daily work.
“There are not a lot of easy bands left, if any, and we need better tools to be able to innovate our way through it,” said Phil Murphy, senior advisor at the National Telecommunications and Information Administration, during a panel discussion at the recent Spectrum Policy Symposium in Washington, D.C., between representatives of NTIA, the FCC, FAA and the White House Office of Science and Technology Policy.
Meanwhile, the telecom industry’s appetite for exclusive-use, licensed spectrum is as bottomless as the mobile data demand that it is trying to meet. A July 2021 report from Coleago Consulting, commissioned by industry group GSMA, estimated that across 36 cities around the world, the average midband (which it considered between 1.5-7.125 GHz) spectrum needs would be more than 2,000 megahertz in the 2025-2030 timeframe—and in high-income cities, midband needs could be as high as 3,690 megahertz to achieve the performance levels expected of 5G.
“There is a concern in the mobile industry that regulators may not be fully aware of the scale of the 5G traffic density challenge in urban areas,” said the report. “Specifically, there is a concern that regulators may not be planning to clear and award enough licensed mid-band spectrum for 5G between now and 2030. There is also a risk that decisions surrounding additional unlicensed spectrum, or 5G spectrum set-asides for local use or for vertical industries, may leave mobile operators with a lack of additional 5G spectrum thus jeopardizing their ability to deliver 5G services and a speed consistent with the ITU-R IMT-2020 vision” of ubiquitous 100 Mbps downlink/50 Mbps uplink performance with up to 1 million connections per square kilometer.
More recently, an Analysys Mason report commissioned by CTIA found that while the U.S. leads 15 global markets in licensed low-band and unlicensed midband spectrum availability (primarily due to the FCC’s decision to make a large swath of 6 GHz spectrum available for unlicensed use), the country is 11th out of 15 in licensed midband spectrum availability. (Midband spectrum here was considered 3-7 GHz and low-band was considered below 3 GHz.)
“The FCC made great progress with recent midband spectrum auctions, but this study shows there is more work to be done. We need Congress, the [FCC] and the [Biden] administration to develop a meaningful pipeline plan to build upon our recent success,” said Meredith Attwell Baker, CTIA president and CEO.
Meanwhile, related spectrum developments include:
-The FCC is currently considering whether to open up 500 megahertz of spectrum at 12 GHz for terrestrial 5G operations. The debate over this has been particularly heated between SpaceX and Dish Network, with Dish advocating in favor of opening up the band and SpaceX insisting that its LEO-satellite-based Starlink service will be disastrously impacted by such a change.
-A newly formed Coordinated Sharing Coalition, which includes the Wireless Internet Service Providers Assocation and Cambium Networks, is asking the FCC to allow spectrum-sharing in 500 megahertz of spectrum at 10.0-10.5 GHz, proposing that the swath of spectrum be used for wireless point-to-point broadband systems and should be governed by an Automated Frequency Coordination (AFC) system.
-A separate, CTIA-commissioned Accenture study suggested that the federal government consider opening up 350 megahertz of airwaves adjacent to existing cellular midband allocations, down to 3.1 GHz (which is already under consideration and study); another 400 megahertz from 4.4-4.94 GHz; and another chunk of 400 megahertz at 7-8.4 GHz. “The current state of spectrum allocation is likely to inhibit the growth and innovation promised by 5G, resulting in negative impacts on the user experience. It could also lead to inefficiencies in network design that will impact multiple spectrum stakeholders (operators, OEMs, and consumers), by requiring more antennas, power, and physical infrastructure, driving up costs,” the report warned. “This spectrum deficit in turn poses a risk of rising consumer prices which could perpetrate barriers to closing the digital divide.”
-The Defense Advanced Research Project Agency (DARPA) is following up its three-year Spectrum Collaboration Challenge, which focused on developing RF systems that could autonomously and dynamically share spectrum, with a new program called Processor Reconfiguration for Wideband Sensor Systems (PROWESS) aimed at developing new classes of receiver processors that are capable of high-throughput, streaming-data processing and reconfiguration in real time to detect and characterize RF signals. “The foundation of RF autonomy is spectrum sensing, but wideband spectrum sensing in an autonomous future pushes edge compute needs far beyond the capacity of today’s devices – and motivates innovation in ultra-flexible, high-throughput streaming data processors,” said John Davies, PROWESS program manager.
At the recent D.C. spectrum policy event, the general consensus was that exclusive licensing will have to continue to be part of spectrum allocations, but that the success of the CBRS auction (in number of participants, if not overall proceeds) showed that there is appetite for shared spectrum, and that the complexity and expense of moving incumbent systems will tilt the balance toward more sharing.
James Linney, director of operations support at the FAA, pointed out during a panel discussion that because of the costs of updating systems, an equipment update by itself may rarely have a business case—but if some incentives were in play for upgrades that could also consume less energy or be more “spectrum stingy”, then multiple interests would benefit. “The win-wins are there, if we look for them,” he said. But, he added, it takes more work and understanding of federal spectrum use than just looking at a spectrum chart and identifying large contiguous chunks to target.
Umair Javed, chief counsel for Rosenworcel, said that developing a spectrum pipeline is too often like playing the card game Go Fish: Essentially, commercial players call out a band, federal users all study their own spectrum cards/holdings, and then someone responds, “Go fish” —in other words, look somewhere else. If all the players involved were willing to put their cards on the table, with transparency and information sharing (and perhaps a role for industry in identifying innovative technology that could come into play), then it might be easier to distinguish between “artificial scarcity” and “actual scarcity” of spectrum. It’s going to take a concerted effort across agencies—and enough RF engineers at those agencies—to make that happen, though.
Several panelists expressed hope that innovative approaches to spectrum sharing will help increase utility and reduce risk for federal users. As spectrum use climbs ever higher, Javed said it is likely that there will be an expanded role for spectrum sharing, given the characteristics of high-band airwaves as well as the realities of the crowded RF environment.
“You don’t build single-family homes in downtown Manhattan,” Javed said.
Meanwhile, based on similar roundtable discussions among various spectrum stakeholders, a recent Aspen Institute report proposes a number of new spectrum policy approaches that could help navigate some of the existing spectrum bottlenecks. The report makes it clear that wireless spectrum increasingly acts as a basis for both U.S. innovation and economic benefit as well as services that both everyday citizens and government agencies depend on, from GPS to weather forecasting to first responder communications and of course, mobile voice and data for an ever-increasing variety of consumer, enterprise and industrial devices.
“Those indispensable services, however, are only a precursor of many more such use cases that we will soon regard as fundamental to a thriving economy and society,” the report says. “The challenge for spectrum policymakers is to ensure that these disparate uses can coexist even as the intensity of use grows year after year.” The report offers suggestions that include, among other things, the development of a new, ten-year spectrum plan that includes opening three to four bands below 15 GHz, each with about 400 megahertz of bandwidth to support the wider channels anticipated to be needed for both advanced 5G and future 6G systems; making mmWave bands license-free to maximize access and encourage innovation; the possible consolidation of multiple federal radar systems onto shared platforms, and development of a joint aeronautical test-and-training network in a higher frequency band; and consideration of a z-axis, or vertical-based element to spectrum licensing, as well as the FCC’s existing information gathering on establishing receiver performance standards that would contribute to efficient use of spectrum.
The Aspen report also urges a broader, more informed and more flexible view of technology enablers in RF, saying: “The spectrum novelties of today may become the predominant network technologies of tomorrow.”
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