Spectrum Sharing in 3.5 GHz Band Citizens Broadband Radio Service

Report and Order Issued April 2015: FCC adopts rules for innovative spectrum sharing techniques to create a new three-tiered commercial radio service spanning 3550 MHz to 3700 MHz (3.5 GHz Band).  The 3550-3650 MHz band segment is currently allocated for use by Department of Defense (DoD) radar systems. The National Telecommunications and Information Administration (NTIA) first proposed making the band available for shared use in its 2010 “Fast Track Report.” On March 24, 2015, NTIA filed a letter recommending a framework that would reduce the geographic area of the zones by approximately 77 percent. NTIA’s letter also recommended the use of sensor technology to permit commercial use inside the zones, providing a roadmap to full nationwide commercial use of the band. Smart grid, rural broadband, small cell backhaul, and other point-to-multipoint networks can potentially access three times more bandwidth than was available under our previous 3650-3700 MHz band rules.

Facilitating More Spectrum Sharing With the new rules, the Commission enables a new model that uses modern technologies – spectrum sensing, cloud computing, and others – to break down some of the old categories: Federal vs. Non-Federal Allocation. Licensed vs. Unlicensed Authorization. Carrier vs. Private Networks.

Spectrum Access System (SAS) This federal/non-federal sharing arrangement is part of a broader three-tiered sharing framework enabled by a Spectrum Access System (SAS). The NPRM proposed that the SAS would accommodate three service tiers: Incumbent Access Priority Access General Authorized Access

Spectrum Access System (SAS) The core functions that an SAS must perform: Determine the available frequencies at a given geographic location and assign them to CBSDs; Determine the maximum permissible transmission power level for CBSDs at a given location and communicate that information to the CBSDs; Register and authenticate the identification information and location of CBSDs; Enforce Exclusion and Protection Zones, including any future changes to such Zones, to ensure compatibility between Citizens Broadband Radio Service users and incumbent federal operations; Communicate with the ESC and ensure that CBSDs operate in a manner that does not interfere with federal users; Ensure that CBSDs protect non-federal incumbent users consistent with the rules; Protect Priority Access Licensees from impermissible interference from other Citizens Broadband Radio Service users; Facilitate coordination between GAA users to promote a stable spectral environment; Ensure secure and reliable transmission of information between the SAS, ESC, and CBSDs; Provide an approved ESC with any sensing information reported by CBSDs if available; Protect Grandfathered Wireless Broadband Licensees until the end of the grandfather period; and Facilitate coordination and information exchange between SASs.

Tier 1: Incumbent Access Incumbent users represent the HIGHEST TIER in this framework and receive interference protection from Citizens Broadband Radio Service users. Protected incumbents include the federal operations, as well as Fixed Satellite Service (FSS) and, for a finite period, grandfathered terrestrial wireless operations in the 3650-3700 MHz portion of the band. Phased in approach: During phase one, a large portion of the country will be available for Citizens Broadband Radio Service use as soon as a commercial SAS is approved and made commercially available. During phase two, much of the rest of the country – including major coastal cities – will be made available for commercial use when no federal incumbent use is detected in a given area Environmental Sensing Capability (ESC) will have to be developed, authorized and deployed. ESC will involve systems of sensors that detect federal uses in and adjacent to the 3.5 GHz band.

Tiers 2 (Priority) and 3 (General Authorized) The Citizens Broadband Radio Service itself consists of two tiers—Priority Access and General Authorized Access (GAA)—both authorized in any given location and frequency by an SAS. As the name suggests, Priority Access operations receive protection from GAA operations. Priority Access Licenses (PALs), defined as an authorization to use a 10 megahertz channel in a single census tract for three years, will be assigned in up to 70 megahertz of the 3550-3650 MHz portion of the band. GAA use will be allowed, by rule, throughout the 150 megahertz band. GAA users will receive no interference protection from other Citizens Broadband Radio Service users.

Tier 2: Priority Access In the Priority Access tier, the Commission authorizes certain users with critical quality-of-service needs (such as hospitals, utilities, and public safety entities) to operate with some interference protection in portions of the 3.5 GHz Band at specific locations. A maximum of 70 megahertz may be reserved for PALs in any given license area at any time and the remainder of the available frequencies should be made available for GAA use. Priority Access Licensees will have more predictable access to spectrum. 10 MHz channel of unpaired spectrum, with census tract-level licensing

Tier 3: General Authorized Access In the GAA tier, users are authorized to use the 3.5 GHz Band opportunistically within designated geographic areas. GAA users would be required to not cause interference to, and accept interference from Incumbent and Priority Access tier users. GAA users will potentially have access to all 150 megahertz in the band in areas where there are no PALs issued or in use and up to 80 megahertz where all PALs are in use Under the license-by-rule framework, GAA users may use only certified, Commission-approved CBSDs and must register with the SAS. Devices operating on a GAA basis must provide the SAS with all information required by the rules – including operator identification, device identification, and geo-location information.

Potential Bandplan -13 dBm/MHz from 0 to 10 megahertz from the SAS assigned channel edge -25 dBm/MHz beyond 10 megahertz from the SAS assigned channel edge down to 3530 MHz and up to 3720 MHz -40 dBm/MHz below 3530 MHz and above 3720 MHz

Future Work April 2015, FCC proposes further study: Protection Criteria for in-band and out-of-band Fixed Satellite Service Earth Stations Appropriate Secondary Market Rules How to define whether PALs are in “use” at a particular location

Future Work May 2015, FCC issues a Public Notice: The wireless industry is developing a version of commercial wireless LTE technology called LTE-Unlicensed (LTE-U) that is intended for operations in certain unlicensed frequency bands. LTE-U could operate in conjunction with licensed commercial wireless services using a technique called Licensed Assisted Access (LAA) whereby a channel in an operator’s licensed spectrum is used as the primary channel for devices operating on an unlicensed basis. The FCC seeks information on these technologies and the techniques they will implement to share spectrum with existing unlicensed operations and technologies such as Wi-Fi that are widely used by the public. A number of organizations have approached the Commission about the development of LTE-U and LAA in the context of the 3.5 GHz and 5 GHz proceedings, which would make spectrum available for general access and unlicensed use, respectively.

Links Report and Order and Second Further Notice of Proposed Rulemaking: https://www.fcc.gov/document/citizens-broadband-radio-service-ro Public Notice: https://www.fcc.gov/document/oet-and-wtb-seek-information-trends-lte-u-and-laa-technology