A group of companies including Qualcomm, Intel and Meta Platforms is asking the FCC to divide the 60 GHz band into three segments so that augmented reality/virtual reality/mixed reality/extended reality (AR/VR/MR/XR) applications can coexist with radar applications in the 57-64 GHz spectrum range that makes up the 60 GHz band.
The 60 GHz band is unlicensed and considered a key band for applications such as AR/VR/MR/XR because it has enough bandwidth and can provide low latency communications.
The companies want to amend the FCC’s Notice of Proposed Rulemaking (NRPM), which would revise transmission power limits for fixed and mobile radar devices that currently operate on an unlicensed basis in the 60 GHz band. The NRPM is looking for input on whether the FCC should permit certain radar devices to operate across the entire 60 GHz band at the same power level currently permitted by communications devices.
The FCC’s NRPM is concerning to Qualcomm, Intel and Meta because the companies believe that revising the transmission power limits will negatively impact latency causing a poor user experience for any AR/VR/MR/XR applications. According to the companies, the FCC NRPM would permit “unfettered pulsing” by radar devices that would increase latency nearly 300%, from 7 milliseconds to more than 20 milliseconds.
The companies note that latency targets for AR/VR/XR/MR applications are not arbitrarily set and that the IEEE and 3GPP standards bodies have specified that these applications need single-digit millisecond latency rates otherwise displays on the applications can flicker and freeze and cause motion sickness.
John Kuzin, VP of spectrum policy and regulatory counsel for Qualcomm, said that the problem with allowing unfettered pulsing by radar devices is that radar devices will continuously pulse. Because communications devices are set to “listen before they talk” if a radar device is pulsing the communications device will wait to communicate. In addition, if a communications device starts to transmit and a radar device begins to pulse, it will interfere with the communications device and its transmission.
“We are trying to put forth an alternative,” Kuzin said. “It’s totally possible to have radar and communications connections using the 60 MHz spectrum in close proximity,” he added.
The proposal
To remove the potential for interference between radar and communications devices, the companies propose that the FCC divide the 57-64 GHz band into three segments:
- The 57-59 GHz band would be reserved for the high-powered radar that may operate with up to 20 decibels per milliwatt (dBm) peak equivalent isotropic radiated power (EIRP), which is the measured radiated power in a single direction. And 13 dBm/MHz peak EIRP power spectral density (PSD).
- The 57-61 GHz band would be reserved for radar devices that use up to 13 dBm peak EIRP, 13 dBm/MHz peak EIRP PSD and a 10% duty cycle in every 33 millisecond interval. In other words, radar that has some silent time.
- The 57-64 GHz band is for radar devices that may use up to 13 Dbm peak EIRP, 13 dBm/MHz peak EIRP PSD and a 10% duty cycle with at least 26.4 milliseconds of continuous silence time in every 33 millisecond interval.
As an example, the proposal says that the Google Soli, which is a miniature radar that tracks real-time motion of the human hand, would fall into the 57-64 GHz category because it pulses for 6.6 milliseconds followed by 26.4 milliseconds of silence in each 33 millisecond period.
Counter-proposal
However, this proposal has many detractors including Amazon, Google, Infineon, Texas instruments. In an FCC filing, these companies asserted that the interference risk to communications devices, including AR/VR/XR/MR applications “would be negligible” if the Commission modifies its rules to allow unlicensed radar devices to operate at higher power than currently permitted.
These companies also offered up a counter-proposal, which they said would promote “reasonable coexistence.” However, this proposal calls for devices with an EIRP level of 10 dBm peak to be bumped up to the 57 GHz to 71 GHz spectrum band and devices with an EIRP level on average of 20 dBm and above to operate in the 57 GHz to 63.72 GHz spectrum.