Samsung Galaxy S3, HTC One S and Nokia Astound supports HD voice feature.
During its CES 2013 press conference, T-Mobile confirmed it's launched a HD Voice service, as well as announcing a $4 billion investment for enhancing its network.
The HD Voice service delivers clear calls between parties, which can only work if both participants have a HD Voice device. Such devices currently include the Samsung Galaxy S3, HTC One S and the Nokia Astound.
As for the $4 billion plan for enhancing its network, the U.S. carrier will launch 4G on the 1900MHz spectrum soon. It's added new coverage to metro markets of Denver, Los Angeles, San Diego and Virginia Beach.
Meanwhile, T-Mobile announced unlimited nationwide 4G is now available with no annual contract. It also confirmed that the Samsung Galaxy S3 is subject to a relaunch soon on its network in order to make it compatible with its forthcoming LTE rollout.