CBRS Is Obsolete, Shouldn't Be Seen as Spectrum Sharing Model of Future: Rysavy
The U.S. shouldn’t look to the citizens broadband radio service band as a model for future sharing if only because it’s based on old technology and doesn’t reflect advances in sharing technology, said Peter Rysavy of Rysavy Research at an American Enterprise Institute 5G forum Thursday. Other experts said the U.S. will be hobbled on spectrum until Congress reauthorizes FCC spectrum auction authority.
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CBRS is based on “obsolete technology” and was “the best solution we could come up with for spectrum sharing a decade ago,” Rysavy said. Networks have since become “much more dynamic” and “can control where the energy goes,” he said. Massive multiple-input and multiple-output, which uses many more transmit and receive antennas to increase transmission gain and spectral efficiency, is already available as part of 5G, he said.
Future sharing should be “based on controlling dynamically where the radio energy goes,” Rysavy said: If sharing is required in the 3.1 GHz band, being studied by the government for 6G, it should be “based on more advanced sharing methods,” he said.
Because CBRS “tries to be a solution for everyone, it ends up being a compromise for everyone as well,” Rysavy said. CBRS operates at low power levels to avoid interference with government operations and is unpredictable because DOD “at any moment can say stop using these frequencies,” he said. “The low power is the real issue for operators” and CBRS requires about seven times more cellsites than are required for C band, he said.
Paroma Sanyal, principal at the Brattle Group, said technological advances alone aren’t enough to ensure U.S. dominance in 5G and the U.S. needs to allocate more exclusive-use licensed spectrum. Wi-Fi offload will help meet growing data demands, but “that is definitely not a solution for not having more spectrum,” said Sanyal, a former FCC economist.
Sanyal said she hears claims that 5G and 6G will offer spectral efficiency that's 10-30 times more efficient than 4G. That’s not quite accurate and reflects results in the lab, not in the field, she said. “No amount of spectral efficiency is really going to get you out of not having more spectrum,” she said: “There is definitely a need now to get more mid-band spectrum into the pipeline.”
Spectrum auctions replaced “a very cumbersome” lottery system, which had more negatives than positives, said Digital Progress Institute President Joel Thayer. For 30 years, until March, the FCC had auction authority, he said. “We are now scrambling” and “that’s a real problem,” he said. “A tool is now taken out of the tool chest,” he said. The delay in granting T-Mobile the 2.5 GHz licenses it won in an auction last year (see 2307070042) “speaks to the issue of how inefficient it is to not have auction authority in play,” he said.
Auctions help guarantee spectrum goes to the company that’s going to use it most efficiently, Sanyal said: “That is something that an auction does really well.” One of the FCC’s success stories was the TV incentive auction, which closed in 2017, she said, and the C-band auction and 3.45 GHz auction were both “extremely successful.”
“I just had no idea that anyone would think to not reauthorize our spectrum auction authority,” said Shane Tews, AEI nonresident senior fellow.
Consumers are just starting to appreciate 5G, Rysavy said. Everything consumers do "simply works better" than with 4G, he said. 5G provides “infrastructure for a lot of economic activity that was not previously possible with 4G,” he said. Bands in the 3-4 GHz range are optimal for 5G, allowing high through-put rates, deployed over large coverage areas, Rysavy said.
Clete Johnson, senior fellow at the Center for Strategic and International Studies, warned of the dangers of losing to China on 5G (see 2307190055). “If China dominates 21st Century technology, they also dominate 21st Century cyber operations, information operations, force projection and, ultimately, weapons systems,” he said: “We cannot fall behind on this. If we don’t lead on 5G, China will.”
The push to reallocate more government spectrum for licensed use is sometimes framed as “trench warfare between DOD and the wireless industry,” Johnson said. “That’s, frankly, a frame that’s very dangerous for our security,” he said. “Commercial strength is national security,” he said.
The “race to 5G” begins in the U.S., Thayer said. “This is not just an American economic issue, this is very much a geopolitical issue and the world is watching,” he said.
China recognizes that 5G provides a “broadband foundation that’s going to enable a lot of industrial and commercial activity” and has allocated three times more mid-band for 5G than is available in the U.S., Rysavy said. That puts the U.S. “at a strategic disadvantage,” he said.