There has been a great deal of lobbying in the USA for higher powered devices to be allowed in the CBRS band in 3.5 GHz, since that would increase the use cases which could be supported, and the commercial value of the networks.
At a recent virtual event held by FierceWireless, one of the FCC commissioners, Michael O’Rielly, hinted that this change might be allowed, something that could boost the prices paid for CBRS licences in the upcoming auction.
Currently, the FCC has approved two classes of CBRS access points with different output power thresholds – Category A with a maximum EIRP of 30dBm per 10 MHz; and Category B, with a maximum EIRP of 47dBm per 10 MHz. However, AT&T has led the call for a Category C to be added, with maximum EIRP up to 62dBm per 10 MHz.
O’Rielly said he had received commitments from the Department of Defense “at the highest levels” to re-examine the power limits once there data starts to be collected from the Spectrum Access Systems (SAS). These will control the three-tiered CBRS system in the 3550-3700 MHz band. This allocates different priority levels to:
- federal incumbents, mainly DoD-related, who always have top priority, but use the spectrum only in certain areas, mainly coastal
- holders of priority access licences (PALs), to be auctioned next month, which will offer relatively short term and localized concessions in 70 MHz of the 3550-3650 MHz portion of CBRS
- and general authorized access (GAA) users, who can transmit in the rest of the 3550-3650 MHz area, and also have the chunk from 3650 to 3700 MHz reserved only for shared access.
The main concerns about potential interference from Category C devices have come from the DoD, which operates coastal radar and other applications in CBRS spectrum. “We’d be able to re-evaluate and very likely increase the power limits in a respectful way to not interfere with the DoD side and other incumbent spectrum users,” said O’Rielly. “We recognize that more power is going to be needed to get more reach and to fulfil all the needs. We have to do so in a thoughtful way, and that’s what I’m working toward.”
Even the likelihood of increased power limits could boost the prices paid for PAL concessions in the auction, wrote Kyung Mun of Mobile Experts in a report.
“Based on this strategic band location, we believe future rule changes for PAL may be possible to support higher power CBSDs as proposed by AT&T last year, he wrote. If so,
“PAL licences may become even more valuable considering that operators can aggregate multiple carriers across CBRS PAL and the potential midband in the 3100-3550 MHz in the future.”
Last week, the FCC released the list of organizations which have registered their interest in taking part in the CBRS PAL auction, scheduled to start on July 23. The four national MNOs – AT&T, Verizon, T-Mobile and Dish – are on the list of course, plus the three biggest cablecos – Comcast, Charter and Cox – and regional telco CenturyLink.
As usual, some well-known names will be hidden behind those of bidding entities, but the most interesting aspect of the list is the presence of several industrial companies from various verticals, including oil majors Chevron and Occidental Petroleum, tower operator CellTex, fiber supplier Corning, agricultural equipment giant John Deere, and several universities such as Duke, Kentucky, Texas A&M and Virginia.
One of the most eagerly watched aspects of the CBRS experiment is whether it will throw open the doors to private and industrial LTE (and future 5G) operators. Already, many enterprises and their suppliers have said they will use GAA spectrum to enable them to design and operate their own cellular networks, ensuring these support their precise requirements in a way that the public networks cannot. But for business critical or high reliability use cases, licensed spectrum would be needed, and while few industries would look to buy a conventional national cellular licence, a local, affordable franchise would lend itself to build-out by a large company, or by a neutral host provider serving a particular region or vertical.
Other potential bidders include smaller operators and cablecos such as US Cellular, Cable One, Mediacom Communications, Cincinnati Bell, Frontier, Windstream, Midcontinent Communications, ATN International and Liberty Latin America.
Another category of service providers which are expected to be active in CBRS are mainly rural wireless ISPS, some of which have already been operating in the 3.65 GHz band, and will have their frequencies repurposed as part of CBRS. Those on the list include Viaero, Union Wireless, Bluegrass Wireless, Carolina West Wireless, LICT Wireless Broadband Company, Nemont Communications, Pine Cellular, VTel Wireless and Broadwave.