On July 13, the Federal Communications Commission (“FCC”) adopted a Notice of Proposed Rulemaking (“NPRM”) that proposes to change the agency’s rules to create opportunities for unlicensed field disturbance sensor (FDS) devices (e.g., radars and motion sensors) that operate in the 57–64 GHz band (60 GHz band). The FCC defines an FDS device as one that “establishes a radio frequency field in its vicinity and detects changes in that field resulting from the movement of persons or objects within its range.”
The NPRM proposes to change the FCC’s rules governing 60 GHz radar and motion-sensing devices without affecting the unlicensed communications device operations and licensed Federal and non-Federal users that share the use of the band. Generally, the NPRM: (1) proposes to reallocate the spectrum so that this band would be shared by new FDS devices as well as existing unlicensed devices and licensed users; (2) would revise the transmission power limits for fixed and mobile radar devices currently operating on an unlicensed basis in the 60 GHz band; and (2) seeks comment on whether the FCC should permit certain radar devices to operate across the entire 60 GHz band at the same power level currently permitted for communications devices.
Background
The FCC’s Part 15 rules authorize low-power intentional radiators to operate on an unlicensed basis in certain bands, including the 60 GHz band. Currently, several categories of devices operate on an unlicensed basis in this spectrum, including wireless local area networking (WLAN) devices, outdoor fixed point-to-point communication links, and field disturbance sensors (FDS) (e.g., radar and motion-sensing devices). Section 15.255 of the FCC’s rules contains specific operational policies and technical parameters for these 60 GHz unlicensed devices and generally limits FDS operations to fixed use (i.e., when radar devices are installed in a permanent location). The only exception for mobile radar operations under the current rules is available when these operations support short-range devices for interactive motion sensing (SRIMS)—devices that capture motion in three-dimensional space using radar technology (e.g., gesture-recognition technology that allows users to interact with devices without needing to touch them). Aside from these limited contexts, the FCC has not allowed general use of the 60 GHz band by mobile radar devices and has maintained strict power limits for both SRIMS operations and fixed FDS operations.
Over the past several years, the FCC’s Office of Engineering and Technology (OET) has granted limited waivers to support growing interest in mobile radar applications using the 60 GHz band. In 2018, OET granted a waiver to allow the use of mobile radar sensors at higher power levels to support gesture-recognition for smartphones and other personal devices. Earlier this year, OET granted several additional waivers to companies seeking to manufacture and deploy in-cabin automotive motion sensors used to monitor for children left in hot cars and trigger other safety alerts. OET also granted a waiver allowing a limited number of radar devices for use in collision-avoidance systems for specialized drone operations. In response to the growing interest in 60 GHz operations, several parties have asked the FCC to revise the applicable power limits to enable expanded mobile radar use of the 60 GHz band. This interest culminated in the FCC’s Technological Advisory Council (TAC) examining the 60 GHz band at its January 14, 2021 meeting, which resulted in a formal recommendation that the FCC initiate a rulemaking to address Section 15.255 and the 60 GHz rules.
Principal Elements of the NPRM
Overall, the NPRM seeks comment on whether the rules related to FDS devices, or field disturbance sensors, are sufficiently broad and flexible to enable the operation of the types of emerging unlicensed devices—especially mobile radars—that use the 60 GHz band. The NPRM also focuses on whether the FCC needs to take additional action to ensure coexistence between FDS devices and communications devices operating in the band. Additionally, although the NPRM states that it is intended to “expand the opportunities for unlicensed FDS operations in the band to the greatest extent possible,” it would terminate the 60 GHz waivers granted thus far to ensure the standardization of any new rules.
Increased Power Levels and Expanded Use of FDS Devices
First, the NPRM proposes to amend the FCC’s rules to allow all FDS devices—including mobile radars—to operate at higher power levels in the 60 GHz band. Currently, the only mobile radar operations allowed in the band are SRIMS devices, and these devices are subject to strict power levels (maximum -10 dBm conducted output power and 10 dBm peak effective isotropic radiated power (EIRP)). The NPRM would eliminate the special provisions for SRIMS devices and allow all FDS devices operating in the 57–64 GHz band to transmit at the following higher power levels (all maximums):
- 10 dBm conducted output power;
- 20 dBm average EIRP;
- 13 dBm/MHz average EIRP power spectral density; and
- 10% duty cycle restriction within any 33 millisecond interval.
The NPRM notes that these proposed changes are intended to allow greater flexibility in mobile radar operations and generally harmonize the FCC’s rules with a European Telecommunications Standards Institute (ETSI) standard in effect since 2014.
The NPRM also would allow all FDS devices to continue operating across the larger 57—71 GHz band at the existing -10 dBm conducted output power and 10 dBm EIRP limits currently applicable to SRIMS devices. Under the proposed rules, fixed FDS devices would remain subject to less-restrictive power limits (40 dBm average EIRP and 43 dBm peak EIRP) when operating within the 61.0–61.5 GHz band segment, and the NPRM seeks comment on whether to expand this provision to apply to mobile FDS devices as well.
In association with the proposed increases in power levels, the NPRM seeks comment on a duty cycle (i.e., transmission time per transmission interval) restriction for 60 GHz FDS device operations. Consistent with the waiver requests granted by OET, the NPRM proposes a 10% duty cycle limit (i.e., 3.3-millisecond transmission time for every 33-millisecond transmission interval). However, the NPRM seeks comment on whether this restriction would facilitate radar coexistence with 60 GHz communication devices that require very high data throughput and very low latency, such as augmented reality/virtual reality/extended reality (AR/VR/XR) applications. The NPRM also seeks comment on alternative coexistence frameworks, including the proposals submitted by a group of 60 GHz stakeholders.
“Fixed” and “Mobile” Use of FDS Devices
Second, the NPRM seeks comment on how the FCC should interpret “fixed” and “mobile” for the purposes of distinguishing FDS devices, as the FCC previously has not addressed whether the Part 15 rules permit something that is inherently mobile (i.e., an automobile) to qualify as “fixed” in certain circumstances. The NPRM tentatively concludes that the FCC should interpret “fixed” FDS operations as “those instances where an FDS device is stationary and is operating at a discrete location for an indefinite—i.e., more than mere transitory—period,” and seeks comment on whether this interpretation sufficiently distinguishes “fixed” and “mobile” FDS devices.
Higher-Power FDS Device Operations in 57–71 GHz Band
Third, the FCC seeks comment on whether it should permit FDS devices to operate at a higher power level in the 57–71 GHz band, as well. Currently, 60 GHz communications devices such as WLAN devices may operate in this spectrum segment at higher power limits (i.e., 27 dBm conducted output power and 40 dBm EIRP), and the NPRM asks whether the incorporation of sensing technology such as “listen-before-talk” capability, a technique the FCC uses in other bands in which radio transmitters must sense the radio environment before starting a transmission, would allow radar devices to operate in these frequencies at the same power levels. The NPRM also seeks input on whether there are other interference avoidance techniques available to ensure coexistence between radar and communications devices. Relatedly, the NPRM seeks comment on what effect such higher-power operations would have on authorized users of the band.
Additional Considerations
Several other discrete issues on which the FCC seeks comment include: (1) expanding the permissible use of 60 GHz unlicensed devices on board aircraft, which the rules currently limit to when the aircraft is on the ground, and, for airborne use, only in closed exclusive communications networks; and (2) potential methodologies for compliance testing of radar devices using continuous-wave, frequency-modulated continuous wave, or pulse/impulse transmissions.
Comment Period
Comments on the NPRM are due no later than 30 days after publication of the NPRM in the Federal Register, and the deadline for reply comments will be 60 days after publication in the Federal Register.
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