As part of an ongoing effort to identify and free up more spectrum for commercial wireless broadband, the Federal Communications Commission (FCC) has released a Notice of Inquiry (NOI) to examine “potential opportunities for additional flexible access – particularly for wireless broadband services – in spectrum bands between 3.7 and 24 GHz.” [1] Specifically, the FCC is seeking detailed comment on three specific sets of mid-band frequencies: 3.7 - 4.2 GHz; 5.925 - 6.425 GHz; and 6.425 - 7.125 GHz. Comments are due on or before October 2, 2017, and reply comments are due November 1, 2017.

The 3.7 - 24 GHz frequency range is allocated to Fixed Satellite Service (FSS), Broadcasting-Satellite Service (BSS), and terrestrial Fixed Service (FS). Spectrum allocated to FSS is used, among other things, to provide broadband Internet service (particularly to rural areas), enable communications on board planes and ships, deliver television programming to cable headends, and provide data connectivity for merchant credit card transactions. Allocations to BSS are used to provide television programming to over 33 million households. Spectrum allocated to FS is used for point-to-point microwave links that support a variety of services, including coordination of railroad train movements, control of natural gas and oil pipelines, regulation of electric grids, and all kinds of backhaul.

The rest of this blog post focuses on the parts of the NOI that cover the 3.7 - 4.2 GHz band.

The 3.7 - 4.2 GHz Band – C Band Downlink (space-to-earth) and Terrestrial Microwave

While the FCC included the 5.925 - 6.425 GHz (C Band uplink) and 6.425 - 7.125 GHz bands in its inquiry, the focus of the NOI is on the 3.7 to 4.2 band for licensed use. The decision to issue the NOI is due in part to a June 2017 petition requesting the initiation of a rulemaking to authorize a new fixed wireless point-to-multipoint broadband service, on a shared basis, in the 3.7 - 4.2 GHz band, which was filed by a group of entities calling themselves the Broadband Access Coalition. [2] The coalition argues that its proposals “would create the only mid-band spectrum allocation authorized for licensed P2MP fixed wireless broadband service to rural, unserved and underserved areas that would enable multiple providers to offer competitive gigabit or near-gigabit service.”

The 3.7 - 4.2 GHz frequency band is allocated exclusively for non-federal use as the downlink portion of the conventional C Band used for fixed satellite service, and for terrestrial fixed service. To provide some perspective, the 500 MHz that makes up the band is more than the total spectrum in use today in the Cellular, PCS, AWS-1, AWS-2, AWS-3, 600 MHz, and 700 MHz bands.

The chunk of spectrum allocated to C Band downlink is used by satellites to transmit from space down to earth (referred to as space-to-earth). The FCC estimates that 48 satellites use the 3.7 - 4.2 GHz band to provide downlink signals of various bandwidths to approximately 4,700 registered earth stations throughout the U.S. The downlink signals transmitted by satellites consist of television and radio programming, as well as international telephone and data traffic. There are potentially tens of thousands of receive-only earth stations in operation that are not registered (cable headends and broadcast radio stations receiving network audio feeds).

The 3.7 - 4.2 GHz band is also used for terrestrial fixed service – 20 megahertz paired channels are assigned for point-to-point common carrier or private operational fixed microwave links. Historically, these microwave networks carried long-distance telephone calls and analog television signals. The total number of fixed service licenses in the band has decreased dramatically over the past 25 years. According to the NOI, there are 119 licenses for fixed services in the 3.7 – 4.2 GHz band. [3]

The FCC’s NOI asks many broad questions about repurposing the 3.7 – 4.2 GHz band for wireless broadband, and invites parties to submit other relevant information that may help inform the FCC. The NOI asks for comments in response to the following questions:

• Should existing service rules be altered to permit more intensive fixed use in the 3.7 - 4.2 GHz band by allowing for the deployment of point-to-multipoint FS broadband services and by making the band more viable for shorter, last-mile point-to-point FS?
• What changes to coordination requirements and technical and operational rules should be made?
• What are the possible mechanisms for sharing between FSS and FS?
• How will rule changes affect existing and future FSS operations, including possible approaches for mitigating harmful interference between different services?
• Is the 3.7 - 4.2GHz band well suited for future mobile broadband deployments?
• How can previous FCC decisions to permit mobile service in other bands that are shared with fixed terrestrial and FSS users inform policy decisions in the 3.7 - 4.2 GHz band?
• Do incumbent FS and FSS operations in the 3.7 - 4.2 GHz band present specific challenges to mobile use that are not present in other bands that are shared with these types of incumbent licensees?
• Are there recent technological advancements that could facilitate the deployment of mobile services and minimize the potential for harmful interference between different types of services in the band?
• Are there recent – or anticipated – equipment features that could enhance the potential for mobile service in this band?
• What licensing and service rules would effectively facilitate coexistence between various licensees in the band and facilitate the deployment of new broadband networks?
• Are there particular licensing frameworks or technical rules that would more effectively promote investment in the band?
• Are there opportunities to create higher-capacity links by licensing larger channels in the band for FS or mobile?
• Are there pairing opportunities between this band and other spectrum bands for fixed or mobile services?
• Given the extensive incumbent use of this band, are there opportunities to incentivize relocation or repacking of incumbent licensees to make more spectrum available for flexible broadband use?
• What are the unique challenges and opportunities that may be presented by the addition of mobile broadband services to the 3.7 - 4.2 GHz band, and what effect might these services have on the appropriate service rules?

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[1] Expanding Flexible Use in Mid-Band Spectrum Between 3.7 and 24 GHz, GN Docket No. 17-183, Notice of Inquiry, FCC 17-104 (Aug. 3, 2017), https://apps.fcc.gov/edocs_public/attachmatch/FCC-17-104A1.pdf.

[2] Broadband Access Coalition, Petition for Rulemaking to Amend and Modernize Parts 25 and 101 of the Commission’s Rules to Authorize and Facilitate the Deployment of Licensed Point-to-Multipoint Fixed Wireless Broadband Service in the 3700 – 4200 MHz Band, RM-11791 (filed June 21, 2017), https://ecfsapi.fcc.gov/file/1062353270786/17062202-1.pdf. The Broadband Access Coalition consists of the following members: Mimosa Networks, Inc., WISPA, Open Technology Institute at New America, All Points Broadband, American Library Association, Amplex Electric, Cambium Networks, Consumer Federation of America, ConVergence Technologies, Inc., Cincinnati Bell Inc., Ethoplex, Intelliwave, Intelpath, JAB Wireless, Inc. dba Rise Broadband, Public Knowledge, Quantenna Communications, Red Spectrum Communications, LLC, Schools, Health & Libraries Broadband Coalition, Sho-Me Power Electric Cooperative, SpeedConnect, and Wisper, ISP, Inc.

[3] NOI at ¶ 15, fn 27. There are 109 licenses in the Common Carrier Fixed Point-to-Point Microwave Service (41 of which authorize temporary fixed stations to use the 3.7-4.2 GHz band in a large geographic area, e.g., multi-state areas), one license in the Local Television and Transmission Service, and nine licenses in the Microwave Industrial/Business Pool.