U.S. wireless carriers Verizon and T-Mobile recently filed requests with the FCC seeking permission to test 5G technologies on 28 GHz spectrum.

In a pending request filed last week, Verizon asked the FCC for a six-month special temporary authorization to conduct experimental operations using prototype equipment in the 27.5 GHz to 28.5 GHz range.

Starting April 1, Verizon said it is hoping to test equipment from Ericsson, Intel, Qualcomm and Samsung on the band within a 1 kilometer radius of its offices in Euless, Texas and South Plainfield, New Jersey. The experimental prototypes will use directional, beamforming antennas, the orientation of which will vary in the horizontal and vertical planes, Verizon said in its application.

According to Verizon, the tests will help “advance an understanding of the characteristics of millimeter wave spectrum (specifically in the 28 GHz band), channel bandwidths, and uplink/downlink ratios for residential and commercial deployments.”

The filing comes after Verizon disclosed the successful completion of a series of other 5G tests with Ericsson, Samsung, Intel and Nokia at Mobile World Congress last month. Those tests included experimental millimeter wave technology from Samsung and Intel, the carrier said at the time.

The move also follows Verizon’s recent deal to acquire XO Communications’ fiber assets, which also saw the carrier lease to XO’s LMDS spectrum in the 28 GHz and 39 GHz bands with an option to buy at the end of 2018.

Shortly before that deal was settled, Verizon filed comments with the FCC urging the commission to make super high frequency spectrum available to mobile operators for the deployment of next-generation 5G services using millimeter wave technology.

In particular, Verizon asked the commission to allow 28GHz and 39 GHz licensees to use their licenses for mobile services and auction spectrum in those bands that is not already licensed. The carrier also encouraged the commission to unify the 37 GHz and 39 GHz bands into a single 3 GHz swath of continuous spectrum that would support the creation of multiple licenses with bandwidths of 200 MHz or more.

The carrier has said previously it is eyeing a 2017 deployment of 5G services, but must wait on the FCC to clear ultra-high-band spectrum.

But Verizon is far from the only carrier looking at 5G technologies in the 28GHz band.

T-Mobile also filed a request at the end of last week seeking approval to test millimeter wave technology in the 28 GHz, 38 GHz and 39 GHz bands near its headquarters in Bellevue, Washington.

In its application, the Un-carrier said it hopes to conduct both indoor and outdoor tests to gather “information on signal propagation between buildings and other critical data informing the broader design of 5G systems.”

T-Mobile said only that it would use equipment from “various” manufacturers, but specified that tests at each of the four locations in and around its Bellevue facility would utilize “fixed transmitters and mobile end-user equipment operating within a maximum radius of 2 kilometers of the fixed devices.”

The Un-carrier is seeking approval for a 24-month test period. The request is still pending, according to FCC records.

Last month, fellow tier-1 carrier AT&T also filed an application with the FCC seeking a three-year license to conduct fixed and mobile tests on the 28 GHz band in Austin, Texas. The carrier also asked for permission to conduct tests on the 3.4-3.6 GHz, 3.7-4.2 GHz, 14.5-15.35 GHz frequencies.

In the application, which is still pending, AT&T said it would use 12 prototypes from a confidential manufacturer within a 5 kilometer radius of its base station.