Evidence-Based Analysis Key in Making Spectrum Available for 5G: NTIA

The work that industry and government are doing addressing “clutter analysis” and dynamic sharing is critical to the future of wireless, Shiva Goel, NTIA senior spectrum adviser, said at an International Symposium on Advanced Radio Technologies (ISART) conference on Tuesday. Goel said the government, working with industry, is making progress. The Denver conference's main focus this week is on propagation models that account for the impact of clutter, including foliage and buildings, on wireless signals.

The national spectrum strategy, released last year, and the implementation plan, released in March (see2403120056), taken together, are “the most comprehensive and far-reaching overhaul of spectrum policy undertaken in decades,” Goel said.

Goel emphasized work that’s starting on the lower 3 GHz and 7/8 GHz bands, which are being studied under the strategy and are the top focuses of carriers for 5G and 6G. Later this month, NTIA’s Institute for Telecommunication Sciences plans to release more than 6 million clutter measurements in the 3 GHz-4 GHz range and make them publicly available, he said. ITS is also starting to measure clutter in 7/8 GHz, he said. “This is what evidence-based spectrum policy looks like,” he said.

“Do this right, and you get more service out to more people,” Goel said. Clutter analysis and more dynamic sharing have proven critical in other bands, starting with AWS-3, auctioned in 2014, he said. Some government systems moved out of the band but needed time to do so, while others remained, he said. “This created a need to coordinate new cellular deployments around those existing federal operations.”

The initial analysis was conservative, but “federal agencies, to their credit, committed to studying improvements over time,” Goel said. A key area of refinement has been clutter models that allow operators to deploy systems more widely, while protecting federal systems, he said.

The 3.45 GHz band, sold at auction in late 2021 and early 2022, requires that winners coordinate with DOD, which operates critical systems there, Goel said. ITS and DOD are working on “higher fidelity propagation models” that could mean greater use of the band in protection zones, he said: “Clutter, of course, is part of that effort.”

Goel said in the citizens broadband radio service band, the search continues for ways to reduce the size of dynamic protection areas around Naval operations. NTIA asked its Commerce Spectrum Management Advisory Committee to look at how to make CBRS work better (see 2312180052), he said. At the top of the list was “better propagation modeling that accounts for clutter.”

NTIA and industry have a similar view about the future of spectrum, Goel said. “Connectivity, data, intelligent applications are growing in importance in just about every aspect of our daily lives,” he said: “We know that demand for commercial spectrum access is continuing to climb as a result.” But federal agencies are also seeing more demands on the spectrum they use, he said.

Clare Allen, chair of an ITU-Radiocommunication (ITU-R) study group on radiowave propagation, said it’s critical that the group's work is based on science. “We consider evidence and build consensus,” said Allen, who also is senior spectrum engineer in the U.K.’s Office of Communications. “We need to ensure that we’re offering impartial advice -- that’s the key thing.”

The models need to be “justifiable,” Allen added. That’s more important than ever in a “world where we need spectrum for everything,” she said. “We have to figure out sharing, and it’s important that the models give a clear picture.”

As her ITU-R study group prepared for the World Radiocommunication Conference in 2019, with its focus on the use of millimeter-wave frequencies for international mobile telecommunications, it became clear that the traditional measurement for clutter loss wouldn’t work, she said. “Lots of people came with lots of measurements and ideas for modeling and that was a very intense year and a half.”

The ITU-R study group is considering using the model it developed to study bands below 10 GHz, which will require additional refinements, Allen said. Discussions are underway, and at times are “heated,” she said. “We still need a few more iterations of the modeling and understanding of the measurements,” Allen said. “You really need to understand what the measurements are” and getting high-elevation measurements can be “trying.”

People come to modeling from different perspectives, said Stephane Gagnon, vice president-research at the Communications Research Centre Canada, a government lab. The government is trying to develop a tool that will work across the country, “where sometimes someone will come to the table with a very specific small use case,” he said. The same discussions are happening in Canada now that are occurring this week at ISART, he said.