Wireless Interests Push Back on Opening 28 GHz Guard Band to ESIMs
Satellite and wireless interests are at odds over whether there still needs to be a 50 MHz guard band in the 28 GHz band as protection for upper microwave flexible-use service (UMFUS) networks. The FCC Space Bureau last month solicited comments in docket 17-95 about communications with earth stations in motion (ESIM) in the 28.35-28.6 GHz band (see 2512190009).
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The FCC allows geostationary orbit (GSO) ESIMs in the 28.35-28.6 GHz band, and the interference potential from non-GSO ESIMs in the 28.35-28.4 GHz band isn't any higher, the Satellite Industry Association said in comments posted Thursday. NGSO ESIMs can reorient their beams to follow the movement of the NGSO satellite, meaning any potential interference would be even more transient than GSO interference, the group said. It also called the 28 GHz UMFUS band "underutilized."
Verizon said NGSO ESIMs operating in the 28.35-28.6 GHz band pose a significant risk of interference to UMFUS operations in the adjacent 27.5-28.35 GHz band. UMFUS operators can't use different filter designs or equipment characteristics for receivers to protect against interference without also eliminating desired in-band signals, the carrier argued.
CTIA urged the FCC to keep the 50 MHz guard band at 28.35-28.4 GHz to protect terrestrial wireless, saying that the agency's 2020 rationale for setting up the guard band remains valid. CTIA and Verizon said in their respective comments that if the guard band is revisited, there should also be studies assessing the impact of ESIM interference. In addition, Verizon noted that satellite operators haven't put up any information about anticipated mobile ESIM deployments in the 28.35-28.6 GHz band.
Since the FCC allowed NGSO fixed satellite service ESIMs in the 28.4-28.6 GHz band, demand for satellite services has grown sizably, while UMFUS deployments have stagnated, Amazon Leo said. "The speculative interference concerns previously raised by UMFUS operators continue to be highly unlikely."
SpaceX called for the FCC to look beyond ESIMs in the 28.35-28.6 GHz band by allowing in-motion use across an array of Ku-band frequencies.