Executive Summary

This report explores a tension in spectrum policy that is unnecessarily limiting public access to the airwaves and the benefits of more intensive spectrum sharing and connectivity. Most spectrum licenses (including federal spectrum assignments) confer exclusive or at least primary rights to transmit on designated frequency bands at specific locations or over defined geographic areas, including inside factories, office buildings, and other facilities owned and controlled by others. This traditional form of licensing precludes property owners from using the spectrum inside buildings under their own control, even if the transmissions are contained and would not cause harmful interference to the primary licensee’s operations outdoors. While unlicensed operations have been authorized, until very recently the rules have not been crafted to distinguish between how access rights could vary based on indoor-only use.

This report explores the policy and technical considerations related to expanding indoor-only authorizations to share more bands, particularly federal bands or sub-bands. For example, controlling the spectrum inside a facility is more practical at higher frequencies where transmissions do not readily penetrate building materials or travel long distances. This concept is particularly relevant now, as the National Telecommunications and Information Administration and Federal Communications Commission (FCC) collaborate to implement the National Spectrum Strategy, which is premised on studying alternative means to expand private sector use of underutilized federal bands, particularly bands occupied by U.S. military systems. Five federal bands that may be prime candidates for indoor-only authorizations—1,675 megahertz in total—are discussed in the concluding chapter.

The potential benefits of different rules for indoor-only use are becoming more evident. In 2020, the FCC adopted an order authorizing low-power, indoor-only (LPI) use of 1,200 megahertz on an unlicensed basis across the entire 6 GHz band (5925–7125 MHz), which was already in use by incumbent licensees that include more than 50,000 high-power fixed microwave links. LPI use of this spectrum indoors is limited to roughly one-fourth the standard power of Wi-Fi, yet is considered extremely useful since the vast majority of internet data (including at least 80 percent of mobile device data traffic) is transmitted indoors and over Wi-Fi.

LPI highlights the potential to authorize indoor-only use in many other bands where users comply with power, device form factor, database coordination, or other technical requirements necessary to protect the primary licensees from harmful interference. And while LPI in 6 GHz is authorized under Part 15 of the Commission’s rules (viz., available for use without a license to anyone meeting specified technical requirements), LPI can be adopted as part of a licensed-by-rule framework or licensed exclusively to select categories of facilities (such as factories and schools). LPI underlays also provide another way to expand on the “use it or share it” approach to spectrum sharing, but without the need for control by a geolocation database.