Aerospace giant Boeing continues to defend its proposal to launch a constellation of low Earth orbit (LEO) satellites in order to offer broadband services to all Americans, similar to the plans of OneWeb and SpaceX, and its latest filing with the FCC addresses concerns brought up by the likes of T-Mobile US, Samsung, CTIA, Straight Path Communications and Nokia.
Much of Boeing’s filing takes direct aim at Straight Path, however, a small company that holds hundreds of 39 GHz licenses, including those it acquired from Winstar, that has been critical of the satellite industry's plans. Boeing said Straight Path’s Oct. 31 analysis confirms Boeing’s technical findings “once Straight Path’s analysis is corrected for the significant errors in calculations and assumptions that Straight Path employed.”
The most significant error, according to Boeing, is Straight Path’s use of an incorrect equation for the model of the Upper Microwave Flexible Use Service (UMRUS) planar array antenna, which results in sidelobes that are “twice as high as would actually result.”
Boeing says Straight Path makes other incorrect assertions about the operations of Boeing’s non-geostationary satellite orbit (NGSO) systems in the 37/39 GHz band, including the assumption that satellites will transmit toward Earth from all angles, including very low elevation angles, despite Boeing’s assurance that its satellites will not transmit at angles below 45 degrees. Boeing also said Straight Path “disregards the transient nature of NGSO interference, acknowledging, but failing to take into account that low Earth orbit satellites move quickly across the sky.”
A Straight Path representative wasn’t immediately available to comment on Boeing’s most recent filing, but if the past is any indication, they’re at opposite ends of the spectrum when it comes to the 37/39 GHz band. Straight Path previously provided analysis of various interference scenarios between fixed satellite services (FSS) and 5G services in the 39 GHz band, and on Oct. 31, Straight Path provided an update, incorporating progress in 3GPP regarding the modeling of 5G base stations and mobile stations. Straight Path focused on the 39 GHz band but said its conclusions were applicable to the 37 GHz band as well.
As for CTIA’s concerns, Boeing says they also require corrections. “CTIA mistakes measurements performed on satellite earth station gateways operating in the uplink direction in the 28 GHz band as being applicable to satellite downlink transmissions in the 37/39 GHz band,” wrote Boeing's counsel, Bruce A. Olcott, in the FCC filing. “CTIA references Nokia’s claim that it conducted measurements showing that earth station gateway transmissions in the 28 GHz band were 20-30 dB higher than the adopted limits.”
“Obviously, localized measurements of uplink emissions from satellite earth stations at distances of less than 200 meters have no bearing on the potential downlink emissions encountered from orbiting satellites located some 1,200 kilometers away from UMFUS receiving equipment,” Olcott stated. “CTIA’s assertions are therefore specious.”
As for Samsung, it, too, got it wrong according to Boeing. “In generating its recommendations for satellite downlink PFD limits in the 37/39 GHz band … Samsung employs calculations that use the 28 GHz as the operating frequency band. The 28 GHz band is used by satellite networks as an uplink band and not as a downlink band. As a result, the PFD levels suggested in the Samsung Appendix are incorrect,” the company wrote, noting what it considers the corrected values.
Addressing T-Mobile’s issues, Boeing says its concern about potential interference is unjustified. “T-Mobile’s concerns that multiple beams employed by an UMFUS end user device may experience more interference is unfounded and such devices are already envisioned and included” by the equivalent power flux density (ePFD) regulations proposed by Boeing, the company said.
Nokia raised a number of questions in comments filed with the commission, and Boeing sought to address those as well, saying it derived UMFUS antenna gain parameters using the 3GPP channel model antenna modeling recommendations for planar arrays, among other things.
Boeing’s proposed NGSO system calls for 2,956 satellites, although the initial deployment would consist of a constellation of 1,396 LEO satellites operating at a 1,200 kilometers altitude. That’s compared to the 4,425 satellites that SpaceX is proposing to operate at altitudes ranging from 1,110 kilometers to 1,325 kilometers. Boeing filed its application with the FCC in June and SpaceX submitted its application to the FCC on Nov. 15.
OneWeb, which has the backing of Qualcomm’s Paul Jacobs and Virgin Group’s Sir Richard Branson, is talking about launching at least 700 satellites as the basis for its LEO constellation, which would orbit at an altitude of 1,200 kilometers. That system calls for low-cost, easy to install Ku-band user terminals, and a small number of globally distributed Ka-band gateway antennas. OneWeb submitted its license application with U.S. regulators back in April.