Verizon says ViaSat analysis for 28 GHz assumes 'unrealistic' scenario on several fronts

As Verizon politely put it in its May 19 ex parte, it "has been engaging" with the satellite industry to mutually explore a "workable satellite-terrestrial coexistence regime" in the 28 GHz band. But so far, it's finding ViaSat's analysis to be unworkable.

It's important to recognize that satellite use of the 28 GHz band is a secondary allocation to terrestrial services, Verizon said in its filing. "ViaSat's analysis thus is not only unfounded but its proposal to limit aggregate terrestrial power limits to protect secondary Ka-band satellite systems is extraordinary and unprecedented," Verizon states. "The risks and likelihood of harmful interference must be accounted for in this analysis."

Verizon's statements are in response to ViaSat's April 21 ex parte letter proposing interference protection levels for satellite operations in the 28 GHz band. Verizon says ViaSat's analysis contains overly conservative assumptions. For example, it only considers two types of terrestrial mobile user terminals (UTs), each transmitting at peak power, 100 percent of the time, and only outdoors.

"UTs, in fact, consist of many different types, which are capable of different peak power levels and indoor (as well as outdoor) operations," Verizon states. "Moreover, UTs typically operate with power control, with only UTs at the cell edge operating at or near peak power levels, while those closer to the base station operate at lower power levels. UTs also are highly unlikely to be in use (i.e., transmitting) at all times."

Consequently, a diverse mix of UTs, some indoors and some outdoors, operating at different power levels and only a fraction of the time, is a much more realistic terrestrial operating scenario, according to Verizon. "Together with additional path and clutter losses, this would result in reduced signal strength received at the satellite receiver."

Two key points that Verizon has put forward are: 1) any potential interference to a satellite receiver will require an extraordinarily large number of UTs transmitting simultaneously toward the satellite receiver; and 2) the likelihood that such a large number of UTs, using steerable beamforming antenna arrays, would be simultaneously transmitting and pointed at a satellite receiver is very low.

In its April 21 ex parte, ViaSat explained that in order to protect satellite receivers from 5G interference, it would be necessary to develop a limit on the aggregate power density received by satellites from all 5G transmitters, and then apportion that limit among the various 5G licensees. "ViaSat believes this can be done in a manner that provides the 5G operators with significant latitude in how they design and operate their networks while still satisfying the limit," the satellite company said.

ViaSat reminded everyone of FCC Chairman Tom Wheeler's remarks at the Spectrum Frontiers Workshop held on March 10, where he described sharing between satellite and terrestrial wireless as being "a two-way street," and expressed "hope that the satellite industry and the mobile industry would get together and work on how they can coexist because the future of spectrum in the 21st century is a future of sharing" and that "there are expectations on the mobile industry to meet the satellite interests in a fair and open and equal manner."

For more:
- see this Verizon filing

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