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Federal Register / Vol. 86, No. 158 / Thursday, August 19, 2021 / Proposed Rules devices have operated at this EIRP limit i.e., 40 dBm average/43 dBm peak for several years without causing harmful interference to other authorized services, such as the Passive EESS
operating at 5759.3 GHz. In addition, the IEEE 802.11 standards groups activity to define channel access protocols to allow transmission of radar signals alongside communication signals may allow coexistence of both signals in the 60 GHz band. The Commission seeks comment on the proposed EIRP level for FDS devices and on the Commissions tentative interference assessment. The Commission also seeks comment on the state of standards development
specifically, with respect to coexistence issues between radar signals and communications signals. Should the Commission specify any coexistence measures or requirements, such as listen-before-talk in its rules? Does the fact that many radars are mobile mean that they will not be used in close proximity to communication devices for extended periods of time, thus limiting any potential for causing interference to short durations? Further, the Commission seeks comment on the benefits or costs of the proposed change to the EIRP limit with respect to 60 GHz authorized users. How would this change, if adopted, benefit stakeholders, consumers and others? Parties that oppose these proposed rules should:
Cite specific harms that they believe will result from changing the rules in the manner proposed, estimate the costs of such potential harms, and specify under what parameters they believe radar systems can coexist with communications systems in the band.
Because 60 GHz FDS devices will need to coexist with 60 GHz communications devices, the Commission also seeks comment on the state of development in the 60 GHz communications device ecosystem.
What is the current state of deployment of 60 GHz communications systems?
What use cases are supported by 60 GHz communications systems today, and what use cases are contemplated for these systems in the future? Do 60 GHz communications systems generally take advantage of the higher EIRP limits permitted under the Commissions rules? Facebook, Intel, and Qualcomm assert that the 60 GHz band will be used by unlicensed devices for latencysensitive augmented reality/virtual reality/extended reality AR/VR/XR
applications. Is this likely to be a widely-deployed use case in the 60 GHz band? Do AR/VR/XR applications present distinct interference scenarios
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or raise other considerations compared to other 60 GHz WLAN applications? Do 60 GHz unlicensed communications systems operate throughout the entirety of the 60 GHz band? Could these systems operate effectively in a subsection of the overall band, for example, the 6471 GHz band segment?
Transmitter Conducted Output Power Limit. The rules currently permit FDS
devices to operate at a maximum 10
dBm transmitter conducted output power, whereas 60 GHz WLAN devices are allowed up to 27 dBm. The Commission proposes to allow FDS
devices to operate at a maximum 10
dBm conducted output power, consistent with the waivers the Commission has already granted in the band. The Commission notes that the ETSI standard specifies the conducted output power as a mean average limit, rather than a peak limit as the Commissions rules do. The Commission seeks input on whether the Commission should consider average transmitter conducted output power limit and what impact this would have on the different types of FDS devices e.g., FMCW, pulse, etc.. On the other hand, the Commission notes that for 60
GHz transmitters, including communications and radar devices, that are implemented at the chip level, access to the transmitter output port may not be available, rendering a demonstration of compliance to this requirement burdensome. The Commission seeks input on whether this requirement is necessary in view of the technological evolution of such system-on-chip devices. A 10 dBm transmitter conducted output power limit along with a 20 dBm EIRP limit implies a limit on transmit antenna gain. The Commission inquires as to whether the transmitter conducted output power limit instead should be replaced by an antenna gain limit. If so, what limit would be appropriate?
Should an antenna gain limit be applied to all 60 GHz transmitters, including 60
GHz communication devices, since these devices also have transmitters implemented at the chip level, and thus would encounter the same measurement difficulties? The Commission also seeks comment on whether a transmitter conducted output limit is necessary for 60 GHz transmitters, including communications and radar devices. The Commission seeks input on this issue in order to develop a comprehensive record. The Commission also seeks comment on the benefits or costs of the proposed change to the transmitter conducted output power with respect to 60 GHz authorized users. Proponents of
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such a change should provide specific details regarding measurement difficulties than might be encountered for system-on-a-chip devices as well as details on what maximum antenna gain they believe should be specified and whether there are circumstances under which that gain can be exceeded e.g., with a corresponding EIRP reduction.
Power Spectral Density Limit. The existing rules do not restrict the power spectral density for 60 GHz devices. The Commission proposes to require a 13
dBm/MHz EIRP power spectral density on FDS devices, to be consistent with the ETSI limit. This is the same restriction the Commission placed on Google and other parties operating FDS
devices pursuant to Commission issued waivers. The Commission seeks comment on the proposed power spectral density limit. Is there a need for a power spectral density limit, and if so, what is the appropriate limit and for which types of devices should it apply?
For example, would a power spectral density limit be necessary for FDS
devices using frequency-modulated continuous wave FMCW, or pulse/
impulse transmissions? Although the Commission is mindful of harmonizing the technical rules that the Commission adopts with the existing ETSI standards, the Commission seeks input and technical analyses on the utility of this proposed requirement. FMCW sensors generally modulate their transmission over a frequency band in order to obtain the necessary target resolution. At any given time, FMCW sensor emissions are limited to a small portion of the spectrum. As such, implementing a PSD
limit appears to be an appropriate measure for spectrum sharing for these types of sensors. The Commission seeks comment on whether a PSD limit alone is a sufficient power limit to facilitate sharing between field disturbance sensors and communication devices.
Are there other FDS modulation techniques that would benefit from a power spectral density limit? The Commission also seeks comment on the benefits or costs of the proposed power spectral density limit for FDS devices with respect to 60 GHz authorized users.
If the Commission does not adopt a power spectral density limit, what are the ramifications if devices are permitted to operate with all of their energy concentrated in a narrow bandwidth? Parties that oppose these proposed rules should cite specific harms that they believe would result by imposing a power spectral density requirement.
The Commission notes that the EIRP, transmitter conducted output power, and power density limits proposed here
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