Google (NASDAQ: GOOG) is fending off calls for extended perimeter protection for incumbent users in the 3.5 GHz band, calling the proposals "overprotective" and warning they could limit spectrum availability.

Federal and non-federal incumbent users operating in the 3550-3700 MHz bands vary in their support for either zone-based or boundary-based protections for radar, satellite and other mission critical operations. But Google says that some licensees recommend a blanket extension of the perimeter of protection for some or all incumbent users.

"For example, some commenters suggest protection radii of at least 6 and up to 24 kilometers around their current operations, regardless of the directionality of their antennas or the presence of CPE in all sectors surrounding a base station. Establishing such indiscriminate protection zones will leave spectrum underutilized," Google wrote in an FCC filing.

Refuting comments made by energy proponents and companies including the American Petroleum Institute and Exelon, Google proposes basing interference protections for installed operations on location, antenna direction and other characteristics.

At stake amid the arguments is 150 MHz of broadband spectrum, which will become available for shared commercial use as part of the FCC's Citizens Broadband Radio Service, a developing set of rules and policies. The FCC has proposed a spectrum sharing system that will assign different protocols among three tiers: federal and nonfederal incumbents, Priority Access licensees and General Authorized Access licensees.

Google has an interest in the proposal not only because it will make more spectrum available for unlicensed use but also because the company is developing a Spectrum Access System (SAS) for spectrum management in the 3.5 GHz. The SAS picked by the FCC will be responsible for dynamically managing traffic among the different tiers of users.

Google could also be targeting the 3.5 GHz band for the deployment of LTE-Unlicensed technology. A Nokia exec in September 2015 said his company was seeing interest in deploying LTE-U from companies like Google, although Google denied interest in putting the technology to work. But traditional operators like T-Mobile (NYSE:TMUS) and Verizon (NYSE: VZ) have expressed interest and have been trialing technologies like License Assisted Access (LAA) and LTE-U for spectrum-sharing operations in 3.5 GHz.

For more:

- read this FCC filing

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