In preparation for the auction of the 100 megahertz of midband spectrum at 3.45-3.55 GHz this fall, the Federal Communications Commission and National Telecommunications and Information Administration have released details on the limited locations in which commercial operators will have to coordinate with federal users.
The 3.45 GHz auction, or Auction 110, is expected to begin in early October.
While commercial network operators will generally have use of the entire band in the contiguous United States, under the FCC’s rules there will still be some locations where federal systems will remain in operation and non-federal systems may be restricted or at least, not entitled to interference protection from those systems. Those areas, the two agencies say, number nearly three dozen around the country, but are “limited in size and scope and include military training facilities, test sites, Navy home ports, and shipyards.” The Department of Defense has been using the 3.45 GHz band for high- and low-powered radar systems, including fixed, mobile, shipborne and airborne systems, as well as testing and training related to those systems.
The places with federal incumbent systems have been dubbed Cooperative Planning Areas (CPAs, of which there are 33) or Periodic Use Area (PUAs; 23 of them overlap with CPAs), where coordination with federal incumbents will be required and operators who win 3.45 GHz licenses are being encouraged to enter into operator-to-operator agreements to figure out the details on efficiently sharing the band in those locations.
In all but two of them, winners of 3.45 GHz licenses have to coordinate operations across all 100 megahertz of the band. But in the Fort Bragg, North Carolina CPA and PUA, licensees will only have to coordinate with federal users in the lower 40 megahertz of the band; and in Little Rock, Arkansas CPA, coordination across the full band will only need to happen for about the first year after the auction, after which federal users will vacate the top 60 megahertz of the spectrum and operate in the lower 40 gigahertz, as at Fort Bragg.
Federal incumbents in the band have to put together transition plans that implement relocation or sharing arrangements, and NTIA plans to publish the ones that are publicly available no later than June 7.
NTIA says that DoD will create a workbook for coordination, as it did with AWS shared frequencies, as well as a post-auction single point of contact on NTIA’s website and an online portal for formal coordination requests. The rules state that no formal coordination requests may be made for nine months after the closing of the 3.45 GHz auction, unless the 3.45 GHz licensee and a federal incumbent agree to make an exception.
Auction 110 will offer up to 100 megahertz of spectrum divided into ten 10-megahertz blocks, licensed by geographic areas known as Partial Economic Areas (PEAs), for a total of 4,060 flexible-use licenses across the contiguous United States.
The FCC has noted that the 3.45 GHz band, plus the neighboring 3.5 GHz CBRS band and the 3.7 GHz C Band spectrum, represent 530 megahertz of contiguous midband spectrum for 5G. Acting FCC Chairwoman Jessica Rosenworcel said that the build-out requirements for 3.45 GHz are the “most aggressive build-out obligations of any spectrum auctioned for 5G to date. … We insist on getting infrastructure built twice as fast as what the agency has required in other recent 5G bands.”