After Straight Path took aim at Boeing's analyses about spectrum sharing in the 37/39 GHz band and called them flawed and incorrect, the aerospace giant shot back, telling the FCC that nothing could be further from the truth.
Straight Path, which has nine employees, filed an ex parte with the FCC on June 14 saying that it disagreed with the Satellite Industry Association (SIA) and Boeing when they told the commission to seek further comment on the use of the 37/39 GHz band before adopting regulations permitting access to the band for mobile broadband operations.
Straight Path, which holds 28 and 39 GHz licenses that once belonged to Winstar, argues that SIA and Boeing should have raised their concerns much sooner and said Boeing's interference analyses between fixed satellite services (FSS) and 5G terrestrial services were based on flawed assumptions that led to incorrect conclusions.
However, Boeing says it is Straight Path that is making the wrong assumptions and conclusions. "Straight Path's technical arguments misstate the capabilities of phase array technologies, do not accurately address the existing and planned satellite uses of the 37/39 GHz band, and fail to acknowledge relevant spectrum studies underway within the International Telecommunication Union (ITU) Radiocommunication Sector (ITU-R)," Boeing told the commission.
Boeing is developing a non-geostationary satellite orbit (NGSO) satellite system that would operate in the V-band. It says its proposed NGSO FSS system would provide very high data rate services to all Americans regardless of their location, finally resolving the divide that exists in the availability of broadband services between urban and rural populations. In contrast, Boeing says, CTIA has acknowledged that terrestrial 5G services are more geared toward densely populated areas and will be used primarily for adding capacity and high-speed data to existing networks with the greatest population density.
While disputing Straight Path's assertions, Boeing refers in its ex parte notice to some of the concepts the cellular industry expects from 5G. Although 5G standards are still being worked out, it's anticipated that 5G base stations will use antennas with large numbers of elements. Phased array technologies also will be part of the mix, and 5G systems are expected to employ highly directional beams and in some cases time division duplexing (TDD) to ensure that no two desired transmissions are arriving at a particular 5G base station from the same angle using the same time segment in a particular frequency band. For this reason, Boeing says, its technical analysis was based on flux density over the entire bandwidth, with only one signal per base station assumed to be present at any time and at any portion of the frequency band.
While it is statistically possible that two or more 5G mobile units in the same area could communicate with different 5G base stations using the same time segments and frequencies, the 5G mobile units will be directing their transmissions toward their respective base stations, which will likely be in substantially different directions. "Thus, although there is some potential for aggregation of 5G interference into satellite earth stations, Boeing's statistical analysis indicates that the potential additional noise is negligible and can be disregarded," the company said.
In sum, Boeing argues that sharing between the mobile and satellite industries is doable, something FCC Chairman Tom Wheeler told both industries they needed to work on. Boeing says it, as well as the rest of the satellite industry, took his message to heart and engaged in significant analysis regarding the technical capabilities that can be used to make millimeter wave spectrum sharing a reality.
Interestingly, while Wheeler and others believe a fair sharing scenario can be worked out, Boeing is suggesting that toward that aim, the locations of 5G base stations should be confidentially disclosed to satellite system licensees operating in the 37/39 GHz band. Boeing says it can use directional nulling and dynamic frequency selection to avoid interference from nearby base stations.
For more:
- see this Boeing ex parte notice
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