AT&T is asking the FCC for Special Temporary Authority (STA) to conduct short-term tests between 3550-3700 MHz in suburban and rural environments in the California Central Valley, including parts of Kern, Fresno, Merced, Tulare, Kings and San Joaquin counties.

The tests will collect Continuous Wave (CW) data for the purpose of propagation modeling study in suburban and rural environments. Fresno and Bakersfield are among the cities where tests are to take place.

“The testing will involve transmissions between fixed stations and mobile stations operating within a 20 kilometer radius of the fixed stations, allowing for an evaluation of path loss characteristics in real-world outdoor environments,” AT&T’s application states.

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The six-month tests will use radio units and antennas that will be deployed outdoors at up to 40 stations using equipment from Berkeley Varitronix Systems (BVS), a New Jersey-based provider of transmitters and test equipment solutions. The antennas will be mounted on rigid masts no higher than 90 meters above the ground level on an existing monopole structure or building rooftops no more than 3 meters above the roof.

RELATED: AT&T Labs wants experimental license to test fixed non-line-of-sight at 3.5 GHz

AT&T is no stranger to the 3.5 GHz band. Last year, AT&T Laboratories was granted an experimental license so that its engineers in Georgia could conduct 3.5 GHz tests on multiple new 5G radio systems with integrated adaptive antennas. It also joined the CBRS Alliance, whose mission is to develop, market and promote LTE-based solutions using the shared spectrum of the 3.5 GHz CBRS band, which the FCC just approved last year for a three-tiered sharing system.

RELATED: AT&T, cable industry signal interest in launching LTE into shared 3.5 GHz band, likely for 5G

Not everyone has been sure to what extent wireless operators would invest in the 3.5 GHz band due to shorter license terms and the uncertainty that brings. While AT&T and CTIA are members of the CBRS Alliance, AT&T remains the sole mobile operator on the alliance's membership roster.

RELATED: AT&T keeps up pressure on FCC to revise PALs for 3.5 GHz

When the FCC back in April 2016 took steps to finalize the rules around the 3.5 GHz band, the two Republican commissioners at the time—current Chairman Ajit Pai and Michael O’Rielly—disagreed with the other commissioners in some key areas. Pai at the time called the 3.5 GHz proceeding an “experiment,” and said he would have liked to have seen greater incentives for providers to invest in the band. He had also advocated to shrink exclusion zones and move more quickly to open them up to consumer use.

Since then, things have been progressing at a reasonable pace. Creation of the standards and protocols for CBRS has been ongoing through the Wireless Innovation Forum (WinnForum), whose members include Federated Wireless, Google, Ericsson, Nokia, Ruckus Wireless and others that are also behind the CBRS Alliance.

The WinnForum in December announced the public availability of its signaling protocols and procedures related to the 3.5 GHz CBRS band—first-of-their-kind standards for 3.5 GHz.

Federated Wireless and Alphabet’s Access team reached an important milestone that same month when they demonstrated interoperability between their Spectrum Access System (SAS). Demonstrating interoperability of the Federated Wireless and Access SASs, which were independently developed, was a necessary step toward launching a commercial shared spectrum service while validating the SAS-to-SAS interface protocol defined by the WinnForum, according to the companies.

Commercial products based on 3.5 GHz, like access points and different radio systems, are expected to be available in the first half of this year, but it’s unclear when support for 3.5 GHz will be fully baked into end-user devices.