T-Mobile has been vocal about urging rule changes for the 3.5 GHz Citizens Broadband Radio Services (CBRS) band, but the Un-carrier is still pushing ahead with testing efforts in the band to help understand propagation characteristics.

On Sept. 18 the operator filed an application with the FCC seeking an experimental special temporary authority (STA) to begin running 3550-3700 MHz band tests starting this October. T-Mobile will test four different units of prototype equipment from Ericsson and Nokia in indoor and outdoor settings prior to equipment certification. 

T-Mobile is requesting to run the trials in Las Vegas, Dallas, and Richardson, Texas.

According to the filing, the prototype equipment will use 20 megahertz of bandwidth and an emission designator of 20M0W7W. The modulation technique is LTE-TDD, utilizing digital OFDM, QPSK, 16QAM, and 64QAM. 

FCC fillings also show that T-Mobile requested a similar license in April to conduct 3.5 GHz trials in Bellevue and Bothell, Wash., using prototype Nokia equipment. However, that application was dismissed because the proposed areas are within the exclusion zone and could not be approved by the Navy.

In June, the Un-carrier urged the Commission to change the CBRS licensing scheme to use partial Economic Areas rather than Census blocks to measure licenses, extend the license terms to 10 years, and make all priority access licenses (PAL) available at auction, regardless of the number of applications received for each.

T-Mobile isn’t the only major operator testing out the 3.5 GHz band. In August, Verizon achieved the first ever use of CBRS band 48 spectrum in an LTE-Advanced demonstration of carrier aggregation working alongside partners Federated Wireless, Ericsson, and Qualcomm.

A Verizon spokeswoman told Wireless Week at the time "it's hard to predict what the FCC may do, so we are continuing to drive towards CBRS with what we know now, and will adapt if necessary."