Wireless and Satellite Continue Clash Over ESIM/UMFUS Guard Band
Wireless and satellite interests are reinforcing their arguments on whether a spectrum slice in the 28.35-28.6 GHz band needs to remain a guard band protecting upper microwave flexible-use service (UMFUS) networks from adjacent-band earth stations in motion (ESIM). Docket 17-95 comments last week saw those interests largely buttress claims made last month as the FCC seeks comments about communications with ESIMs in the 28.35-28.6 GHz band (see 2601220027). In comments posted Friday, wireless interests also pushed back on SpaceX calls for the FCC to green-light ESIM operations across a wider array of Ku-band frequencies.
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Absent some satellite technical analysis of non-geostationary orbit ESIM operations, the 50 MHz guard band at 28.35-28.4 GHz protecting UMFUS needs to stay, CTIA said. There's no need to increase the interference potential by NGSO ESIMs into the 28 GHz band given the 1,200 MHz of Ka band spectrum available to them, it said. Adaptive array antennas used by NGSO ESIMs carry greater risk for potential adverse impacts on "newer, more sensitive" customer premises equipment used for fixed wireless access, CTIA said.
The existing out-of-band emissions (OOBE) limits weren't designed to protect UMFUS from ESIM terminal interference, and fail to do so, Verizon said. The guard band is "an efficient and straightforward" way of protecting UMFUS from NGSO ESIM OOBE spillover into the 27.5-28.35 GHz band, it added. While the FCC wanted to update the record, satellite interests haven't offered any new information about expected ESIM deployments or operational information, such as ESIM antenna performance and power control techniques, it said.
SpaceX said wireless industry arguments for the 50 GHz guard band are groundless, adding that millimeter wave propagation characteristics and NGSO ESIM operational characteristics show that the risk of harmful interference to adjacent-band operations "is minimal." Even if there's harmful interference, the existing OOBE limits have shown they protect those operations from it, it said. SpaceX questioned whether there are even many terrestrial upper microwave deployments to protect. It said that with terrestrial 5G deployments in the upper microwave bands largely limited to indoors and high density uses, satellite operations "are completely obstructed from causing interference" anyway.
NGSO ESIMs are a no bigger interference risk than the millions of NGSO and geostationary orbit fixed earth stations and GSO ESIMs operating in the 28.35-28.6 GHz band nationwide for years without causing interference with UMFUS, said Amazon Leo.
SpaceX last month in the docket said any updated ESIM rules should allow use of phased array terminals anywhere in the Ku band where satellite services could improve in-motion satellite broadband. In last week's comments, CTIA said SpaceX calls for broad NGSO ESIM access in the Ku band, including the 13 GHz band, go way beyond the proceeding's scope. It added that ESIM access in the 13 GHz band raises big technical issues, and any expansion of ESIM services needs to be evaluated band by band. Verizon also said SpaceX was going beyond the scope of the proceeding.