Major US operators are now working with unlicensed spectrum to boost 4G capacity and speed: T-Mobile says it has launched LTE-U in six markets, while AT&T has completed LAA trials with Ericsson in San Francisco.

T-Mobile US Inc. says that LTE-Unlicensed (LTE-U) at 5GHz is now live in Bellevue, Wash.; Brooklyn, NY; Dearborn, Mich.; Las Vegas, Nev.; Richardson, Texas; and Simi Valley, Calif., with more locations coming. Subscribers will need a compatible phone to access the additional 5GHz bandwidth, such as the Samsung Galaxy S8. We've asked T-Mobile for a list of compatible devices.

Part of the T-Mobile focus for LTE-U is using it in outdoor small cells for improved coverage. Karri Kuoppamaki, VP of radio network technology and strategy at T-Mobile, said last week that the operator has "contracted ... for 25,000 small cells over the next few years," without specifying how many will be compliant with LTE-U or License Assisted Access (LAA).

Both AT&T Inc. (NYSE: T) and T-Mobile want to use the 5GHz spectrum to boost the depth of spectrum channels on their network. This means bonding radio channels to push aggregated spectrum capacity to 60MHz, 80MHz or above, and to boost LTE download speeds to multiple hundreds of Mbit/s.

T-Mobile said on Sunday it tested LAA downloads at 741 Mbit/s in 80MHz of spectrum. AT&T, meanwhile, said Monday it conducted LAA field trials with Ericsson, reaching initial download speeds of over 650 Mbit/s. (See LTE-Advanced Pro: Creeping Into Networks Near You.)

AT&T says that carrier aggregation with LAA will be part of its "5G Evolution" LTE-Advanced network updates this year. (See Surprise! AT&T Markets 4G Advances as '5G Evolution' and AT&T Expects 5G in Late 2018 or Early '19.)

The FCC approved the use of unlicensed LTE equipment from Ericsson and Nokia by US carriers back in February. Light Reading noted in April that unlicensed would be a big focus for operators in 2017 and beyond. (See T-Mobile Promises LTE-U Services in the Spring and Unlicensed: It's What's Next for US Mobile Operators.)

— Dan Jones, Mobile Editor, Light Reading