AT&T expanded its fastest wireless service to a second city on Wednesday, with plans to start hitting some of the biggest metro areas in the country by year end.
The faster service, which AT&T has branded "5G Evolution" even though it is still based on 4G LTE technologies, can double the download speeds of the newest phones such as Samsung's Galaxy S8, AT&T said. True 5G mobile networks, which could be up to 10 times faster than the current system, are still a little over a year away, AT&T said.
The carrier added the faster network for customers in Indianapolis, following earlier deployment in parts of Austin.
But by year end, AT&T (t) said it would expand to over 20 cities including Atlanta, Boston, Chicago, Los Angeles, Nashville, and San Francisco. The speed increase relies on technologies that can let a phone communicate over three spectrum bands simultaneously, cram more data into each transmission and use multiple antennas at once.
Get Data Sheet, Fortune's technology newsletter.
All of the big mobile carriers are deploying similar technology this year to speed up their wireless networks while the standards and gear for even faster 5G networks are still in development. T-Mobile (tmus) has said it deployed the faster 4G network features in almost 300 cities. Verizon (vz) says its "LTE Advanced" network is in 500 cities, but only claims a 50% speed increase.
The same three technologies that are speeding up 4G networks will also be utilized for 5G, which will allow a wireless phone user to download an entire high-definition movie in 30 seconds. But no 5G-compatible phones have been announced yet.