By Kelly Hill

T-Mobile US has received permission from the Federal Communications Commission to test its recently won 3.45-3.55 GHz spectrum, to get a sense of operational characteristics in dense urban areas prior to deployment.

According to filings with the FCC, T-Mo will be testing up to 40 megahertz of the midband spectrum in and around specific locations in Dallas, Texas; Kansas City, Missouri; New York City; and Seattle, Washington.

In Dallas, Kansas City and Seattle, the carrier plans to test the spectrum at 3.45-3.49 GHz; in New York City, it will test 3.49-3.53 GHz. Its permission to do so runs through October 2022.

T-Mobile US won 199 licenses in 79 Partial Economic Areas during late 2021 midband spectrum auction known as Auction 110. Those 199 licenses did not include one covering Seattle, but the carrier requested testing use of that area anyway, because that’s where its national testing lab facilities are located. T-Mo also did not win all 40 megahertz across the markets it will be testing; it has been granted permission to conduct its temporary testing in spectrum that was won by other bidders. (Bidders in the auction were not allowed to accumulate more than 40 megahertz of spectrum in a given PEA, and are not allowed to hold more than 40 megahertz of the band for four years post-auction.)

The carrier said in its filing with the FCC that the agency’s Wireless Telecommunications Bureau has not yet processed the post-auction, long-form applications for the 3.45 GHz licenses, and that the carrier “therefore expects that it will be several months before it and others obtain licenses for the spectrum won. T-Mobile wishes to make productive use of the spectrum it won as soon as possible after it receives its licenses. It also wishes to evaluate new technologies across wider bandwidths in densely populated markets, which will provide T-Mobile with valuable operational data prior to introducing service.”

The carrier requested Special Temporary Authority (STA) permission to “generally assess the use of facilities in the band and particularly how networks incorporating the maximum amount of contiguous 3.45 GHz spectrum permitted by the Commission’s rules in densely populated markets can be optimized. That, in turn, will accelerate T-Mobile’s ability to provide innovative services using 3.45 GHz spectrum in the future.”

The carrier plans to use multiple transmitters from Nokia and Ericsson and about 15 prototype handsets in order to conduct its testing. It will test signal levels at various distances to assess coverage characteristics and whether the band can be deployed with existing sites.

T-Mo’s application for the STA illustrates some of the complexities that will be in play for winning bidders of the 3.45 GHz spectrum. There are nearly three dozen areas around the country where licenses winners will have to coordinate their use of the band with existing incumbent military systems; those areas include military training facilities, US Navy home ports, shipyards and military test sites across the Western US and the Midwest and up the East Coast. The Department of Defense has used the 3.45 GHz band for high- and low-powered radar systems, including fixed, mobile, shipborne and airborne systems, as well as some defense contractors’ facilities for testing and training related to those systems.

The carrier told the FCC that its testing would not affect any federal operations in Kansas City or New York City, but it had to get more granular in the Dallas and Seattle areas. In Seattle, T-Mo will be conducting its testing in an area that overlaps with a Bremerton, Washington coordination area with federal users—but the carrier says it won’t be operating within the specific census tracts where the Department of Defense requires protection. T-Mo will also be testing within 50 kilometers of facilities used for aerospace and defense testing by government contractors Boeing in Texas and Raytheon in Seattle—but again, the carrier says that by FCC rules, it only owes protection to incumbent operations in certain census blocks that the DoD has specified as requiring interference protection.

The 3.45 GHz auction, also known as Auction 110, was held in late 2021 and offered up 100 megahertz of prized midband spectrum, divided into ten 10-megahertz blocks, licensed by geographic areas known as Partial Economic Areas (PEAs), for a total of 4,060 flexible-use licenses across the contiguous United States.

In related news, AT&T was granted an STA from the FCC last week to expand its ongoing testing of 3.45-3.55 GHz to 25 sites, including both indoor and outdoor locations.

Meanwhile, Booz Allen Hamilton—which has won hundreds of millions of dollars in contracts to integrate and test 5G systems for the Department of Defense—was also granted an STA for 3.45-3.55 GHz spectrum to conduct “short duration low power itinerant operation … to perform 5G system technical demonstrations to military and government officials” in the Tampa, Florida area during the course of this week.

Additionally, T-Mobile US received a separate STA this week to test the 6.11-6.19 GHz portion of the 6 GHz band at two locations in Alexandria and Falls Church, Virginia. That testing will involved two fixed access points and up to 10 user devices to test Wi-Fi 6 capabilities and performance.