Internet, Chip Firms Present Engineering Study Showing No 6 GHz Interference
Friday, July 05, 2019 | Comments

A group of high-tech internet, wireless and semiconductor companies made a presentation to the FCC outlining an engineering study that the companies said showed that 6 GHz radio local area network (RLAN) operations will protect fixed service (FS) links from interference.

Representatives from Apple, Broadcom, Cisco Systems, Facebook, Google, Hewlett Packard Enterprise, Intel, Marvell Semiconductor and Qualcomm met with officials from the FCC’s Office of Engineering and Technology (OET) to present the study June 20.

RKF Engineering prepared the study. The Association of Public-Safety Communications Officials (APCO) International questioned the validity of a 6 GHz analysis by RFK Engineering last year. Verizon and the Fixed Wireless Communications Coalition (FWCC) echoed APCO’s concerns, saying the study relies on “averages of averages” to hide the severity of the interference of uncontrolled RLANs to FS links.

The latest RKF analysis included simulated RLAN-to-FS interactions including both free-space propagation conditions and 0 dB of building entry loss — and in rare cases less than 0 dB. For each of the about 1 billion RLAN devices “dropped” in each run of the RKF Monte Carlo simulation, the simulation algorithm selected values at random across the entire range of each of these distributions, in proportion to their respective probabilities. Thus, for example, among RLAN devices 5 kilometers away from a given FS receiver, the selected propagation values resulted in approximately 25% exhibiting free-space path loss, and approximately 45% exhibiting 130 dB of propagation loss or less. Similarly, for building entry loss, values for indoor RLAN devices were selected at random such that, for example, roughly 50% exhibited building loss of 19 dB or less, and 10% exhibited 6.5 dB or less, the ex parte filing said.

“We additionally discussed that RKF was even more conservative than this, as it did not account for the fact that real-world RLAN devices typically have multiple antennas which transmit at peak EIRP (effective isotropic radiated power) in only a single direction, with substantially lower emissions in other directions, thus further limiting the total energy an FS could receive from an RLAN device,” the letter to the FCC said. “We presented results from empirical measurements of existing RLAN devices to confirm these conclusions. The fact that RKF did not take this factor into account, instead assuming that devices could transmit peak system power in the direction of an FS, makes its analysis even more conservative.”

Last October, the FCC proposed making up to 1,200 megahertz of spectrum available for use by unlicensed devices in the 6 GHz band (5.925 – 7.125 GHz), despite numerous mission-critical communications industry concerns and filings.

The full letter and presentation from the wireless and internet companies are available here.

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