FCC Exploring Use of Small Cells in 3.5 GHz Band

Use of the band would be managed by a spectrum access system and include a dynamic database and possibly interference mitigation techniques, officials said. The rules propose a priority access tier for use by hospitals, utilities, first responders and other entities with critical needs who would operate with some interference protections in parts of the band in designated areas. In a general access band, the public would be permitted to use the band on an “opportunistic basis,” though their use would be subject to interference.

Setting aside the band for small cells was one of the recommendations in the President’s Council of Advisors on Science and Technology’s (PCAST) controversial spectrum sharing report (CD July 23 p1). In a presentation to the commission, Wireless Bureau Chief Ruth Milkman held up a box the size of a transistor radio to show how tiny a small cell can be.

"Where we can’t practically clear and reallocate government spectrum, and that’s always the fist choice, there may be ways to maximize use of spectrum through sharing concepts,” said FCC Chairman Julius Genachowski. The order should also lead to greater use of small cells in the nation’s mobile networks, he said. “It’s a very important revolution.” While the use of higher power transmitters would mean big exclusion zones across the U.S., “with small cells we have the potential … to free up spectrum across virtually the entire country.”

Commissioner Robert McDowell, who disputed many of the findings in the PCAST report, said he nonetheless supports launch of an NPRM. “Just as with our efforts to introduce unlicensed low-powered commercial services in the TV white spaces, a project that I have ardently supported for many years since my arrival at the Commission, I am hopeful that this experiment in the 3.5 GHz range will promote additional innovation that could be useful to consumers in other bands,” he said. “Our decision to ensure development of a comprehensive record through additional notices, analyses or white papers, prior to releasing final draft rules is consistent with this educational approach."

One big issue the NPRM raises is whether the FCC can keep exclusion zones relatively small, said Commissioner Ajit Pai. “Approximately 60 percent of the U.S. population would not be able to use the 3.5 GHz band under the exclusion zones proposed in the National Telecommunications and Information Administration’s Fast Track Report,” he said. “This is especially troubling because the substantial majority of spectrum-limited markets fall within these zones. For example, if we cannot shrink these zones substantially, the 3.5 GHz band would not benefit Americans who live in New York City, Boston, Philadelphia, Washington, D.C., Miami, Tampa, Orlando, Atlanta, New Orleans, Houston, Dallas, San Diego, Los Angeles, San Francisco, Portland, Seattle, and Denver. … I hope that small cells will enable us to have much smaller exclusion zones and that commenters will provide us with valuable feedback on this issue."

Commissioner Jessica Rosenworcel said the NPRM offers a “peek into the future” of wireless. “Small cells can expand connectivity and facilitate more efficient use of existing frequencies,” she said. “They can cover areas that cannot be reached using macro cell services and at the same time do not present the same interference risk. In fact, the very physical characteristic that was once considered a weakness of this band -- its short propagation distance -- can be turned into its strength. How cool is that?"

"This item is a terrific start to adopting the first element of the PCAST recommendations -- commercial services sharing 100 megahertz of spectrum, in the 3550 and 3650 MHz bands that is currently allocated for federal agency use,” said Commissioner Mignon Clyburn. “In the structure for licensing and using the 3.5 GHz band, the NPRM incorporates two new technological advances that can substantially increase our nation’s efficient use of spectrum. First, greater use of small cell network deployments, much like the small cell architecture, that large wireless carriers use now to offload their smartphone traffic on to unlicensed Wi-Fi networks. Second, it proposes a Spectrum Access System that would employ the concepts used, to establish the successful TV white space databases."

"Today’s action is an important first step in the process of increasing wireless data capacity by 1000 times over the next ten years, which we see as the major challenge that the wireless industry and the US government must work together to meet,” said Dean Brenner, senior vice president-government affairs at Qualcomm, in a statement. “Small cells, when deployed in conjunction with macro cells using smart network technology, will expand capacity substantially, enhance network coverage and reliability, and even improve position location accuracy. Small cells will require a predictable quality of service, and, therefore, the spectrum must be shared on an authorized basis. We look forward to working with the FCC and all stakeholders as the 3.5 GHz proceeding unfolds."

The proceeding “can produce a win-win outcome, where the Navy uses a portion of the total capacity of the band exclusively and unlicensed and lightly-licensed users use another portion on a low-power, small-cell basis that will protect existing military uses and thereby expand access to wireless broadband nationwide,” the Wireless Innovation Alliance said. “After careful and exhaustive planning to avoid harmful interference occurrences within and surrounding it, we believe that the 3.5 GHz band could be used advantageously for small cell use, and that more efficient use of this band could help decrease congestion in other bands,” said Telecommunications Industry Association President Grant Seiffert.