Wednesday the FCC announced a proposal to make available 100 MHz of shared spectrum in the 3.5 GHz band using small cell and database technologies. The Notice of Proposed Rulemaking (FCC 12-148) has the details. The NPRM also seeks comment on including spectrum at 3650-3700 MHz, immediately adjacent to C-band downlink spectrum. The FCC calls the new service in the 3550-3650 MHz band the “Citizens Broadband Service” (CBS) and proposes three tiers of service (1) Incumbent Access; (2) Priority Access; and (3) General Authorized Access (GAA).
Incumbent Access (IA) would consist solely of authorized federal and grandfathered licensed FSS (Fixed Satellite Service) 3.5 GHz band users. These users would be protected from the other tiers by regulation and technical means, including the use of exclusion zones where other CBS uses would not be permitted.
Priority Access (PA) would be given to small cell use by certain critical quality-of-service dependent users at specific target locations, such as hospitals, utilities, state and local governments, “and/or users with a distinct need for reliable, prioritized access to broadband spectrum at specific, localized facilities.”
General Authorized Access (GAA) would allow opportunistic use of the spectrum for a variety of residential, business and enterprise purposes. They would have to protect Incumbent Access and Priority Access users through technologies including geolocation and would not have an expectation of protection from harmful interference. If the FCC includes the 3650-3700 MHz band in the CBS, wireless Internet service providers using this band for links would have to be licensed under GAA rules.
The NPRM proposes a “Spectrum Access System” (SAS) which would govern interactions between devices in the 3.5 GHz band. It would be modeled after the TV White Space database concept. Devices would be limited to 1 W. EIRP.
Users of C-band downlinks are likely to be concerned with widespread use of 3650-3700 MHz, even for “small cell” systems. The FCC addresses this in the NPRM, stating, “We are not aware of any known out-of-band emission issue in 3650-3700 MHz with neighboring bands. We note that the current deployment in 3650-3700 MHz band is subject to geographic protection requirements for federal and FSS facilities and there is also a coordination requirement, which may be why there is no interference issue. Understanding the current operating environment in the 3.5 GHz Band, we seek comment on measures for limiting OOBE from Citizens Broadband Service systems into the adjacent bands. We seek comment on the appropriate OOBE limit for small cells in the 3.5 GHz Band.
The commission also asked about interference protection threshold limits of relevant services in adjacent bands.
If the term “Citizens Broadband Service” has a 1970's ring to it, this is no coincidence. The FCC is proposing to license users under Section 95 of the FCC Rules, Personal Radio Services. That’s the same section that includes Citizen's Band (CB) radio.
Doug Lung is one of America's foremost authorities on broadcast RF technology. He has been with NBC since 1985 and is currently vice president of broadcast technology for NBC/Telemundo stations.
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