In meetings with the FCC staff last week, it’s clear that CTIA remains concerned about the potential for interference from satellite operations into terrestrial mobile use in the spectrum bands above 24 GHz – the so-called millimeter bands that are a crucial part of wireless carriers’ plans for 5G.
During the meeting, CTIA highlighted recent measurements that show a potential for harmful interference from satellite operations to terrestrial mobile services. CTIA pointed to measurements conducted by Nokia and pressed the need for additional studies to give the commission enough information to address the “real world” effects of interference from satellite operations into terrestrial mobile use.
“CTIA and Nokia explained that measurements conducted by Nokia show that, in the 28 GHz band, emission levels are higher and impact a greater angular area as compared to the adopted PFD [Power Flux Density] limits of -77.6 dBm/m²/MHz,” CTIA said in its filing (PDF). “Nokia’s measurements reveal that: 1) the measured levels were higher – typically 20-30 dB above the adopted limits; 2) the PFD levels measured in the vertical plane were typically 1-2 dB higher than the horizontal; 3) the measured levels to the sides and rear of sites were higher than expected; 4) there was no roll-off as a function of the azimuth angle as SIA argued there would be; and 5) there were equal levels of PFD at all angles – an approximate 10 dB reduction as compared to the 0 degree measurement.”
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Separately, Nokia presented to the FCC the results (PDF) of two of its studies, including a 63-page report on measurements of Fixed Satellite Services (FSS) earth station spillover emissions to evaluate potential interference levels to nearby 5G systems in the 28 GHz band. Nokia provided a sampling of measurements of PFD from FSS earth stations at various distances and azimuth angles from the FSS sites that the FCC can use to compare with the PFD limit of -77.6 dBm/ m²/MHz proposed in the 28 GHz rules.
In its conclusions, Nokia said AT&T, Nokia, Samsung, T-Mobile and Verizon, collectively in a joint filing, indicated that interference from existing transmit FSS earth stations into 5G networks can be controlled by limiting the PFD at 10 meters above ground level to -77.6 dBm/ m²/MHz at a distance of 200 meters.
“Based on the measured data, it can be concluded that the emission levels are higher and impact a greater angular area as compared to the information previously shared by the ‘Joint Filers’ with the FCC,” Nokia stated.
Nokia previously has noted (PDF) that it was instrumental in leading industry efforts to coordinate future coexistence of 5G networks with FSS in the 28 GHz band. In fact, Nokia led a series of meetings with terrestrial wireless service providers and individual satellite operators, convened through the Satellite Industry Association, to exchange information on the technical parameters of terrestrial operations and satellite operations in the 28 GHz band.
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Nokia last week also submitted a presentation on fixed service 5G coexistence at 70/80 GHz, whereby it studied coexistence of fixed links with 5G systems, including a technique of shutting down 5G beams, which proved to be effective in mitigating 5G-into-fixed link interference “while keeping the performance of the 5G system acceptable,” Nokia said in its ex parte filing.