AT&T, T-Mobile, Verizon respond to satellite's 28 GHz sharing concerns

After satellite players O3b Networks and ViaSat submitted studies to the FCC, AT&T (NYSE: T) Services, Nokia (NYSE:NOK), Samsung Electronics America, T-Mobile USA (NYSE:TMUS) and Verizon (NYSE: VZ) responded in kind, submitting results of a detailed but preliminary simulation conducted by Nokia to assess potential interference between terrestrial 5G services and fixed satellite services (FSS) systems sharing the 28 GHz band.

According to the mobile players' May 6 ex parte filing, the simulation Nokia conducted demonstrates that interference from existing transmit FSS earth stations into 5G networks can be addressed by requiring those satellite earth stations to reduce their power flux density (PFD) at 10 meters above ground to -77.6 dBm/m2/MHz at 200 meters. It also shows that limitations on Upper Microwave Flexible Use (UMFU) licensees are not required to manage aggregate interference from 5G networks into existing FSS receivers that are part of current FSS geostationary or non-geostationary operations.

The filing goes on to say that the interference studies by O3b and ViaSat suffer from inconsistencies and technical limitations. "Perhaps most troubling, both of the studies assume different, and more lenient, levels of protection to safeguard UMFU operations against FSS interference, as opposed to the very stringent protection threshold applied to their own FSS systems," the mobile signatories stated.

While it would seem that the mobile and satellite players are at an impasse, Nokia and partners say they're committed to working with both the Satellite Industry Association (SIA) and its individual members to refine and improve the analysis of sharing at 28 GHz. FCC Chairman Tom Wheeler back in March first sternly urged the SIA and its members to find technical solutions to sharing; he later clarified that it's a two-way street, and both mobile and satellite industries need to step up to the plate. Now, it appears, they're both conducting separate feasibility studies but continue to disagree over complicated technical matters.

Importantly, Nokia's study uses SIA-provided parameters that are very conservative in a number of respects, according to the mobile industry group. "As an initial matter, the satellite noise and receive beam gain figures are based on the most sensitive projections about future, planned satellite network deployments, not necessarily satellite networks that currently exist. Thus, it is unclear whether the SIA parameters are realistic in an environment where a mere 3 dB difference in the receiver sensitivity and FSS antenna gain can change the aggregate interference results by a factor of 2."

Meanwhile, representatives of the SIA Regulatory Working Group (SIA RWG) met with FCC staff on May 9 to discuss the same proceeding on spectrum bands being eyed for 5G. As part of their presentation, they said the satellite industry is committed to working with the wireless industry to achieve a "win-win" solution for satellite and terrestrial. Besides the need to protect FSS use in the 28 GHz and 37/39 GHz bands from harmful UMFU interference, they stressed that the 37/39 GHz band is an important expansion band for satellite.

"SIA is working with terrestrial providers on technical parameters to understand how to mitigate interference," SIA said in the filing, with further analyses from SIA's members to be submitted shortly. 

In a separate ex parte filing, Samsung provided technical data on power and emission limits and discussed updating RF exposure rules for 5G.

For more:
- see this joint filing
- see this SIA filing
- see this Samsung filing

Related articles:
ViaSat responds to Verizon, Samsung, Qualcomm, et al in 5G spectrum quarrel
O3b throws water on idea of near-term solution for 28 GHz sharing
AT&T/EchoStar proposal for 28 GHz sharing gets heat from other satellite players
Verizon promises to work with satellite industry on potential interference issues in 28 GHz band