Beginning May 23, AT&T is introducing High Definition (HD) Voice on an all-IP, Voice Over LTE (VoLTE) network in select markets. At AT&T, you won't have to choose between faster data speeds and crystal clear conversations. HD Voice customers can simultaneously talk while surfing the Web at 4G LTE speeds, all on the nation's most reliable 4G LTE network – it's the best of both worlds.
T-Mobile currently offers HD Voice, however they use the AMR-WideBand (AMR-WB) codec on their old 3G WCDMA network. AT&T has decided to go the different route and push all calls through their LTE Network and use the AMR-WB codec there. Currently, all voice calls go through the 3G network and all data goes through the 4G LTE network.
The current iPhones do not support VoLTE, although their chipset does -- so Apple could update devices like the iPhone 5 to support AT&T's version of HD Voice and VoLTE. However, it is very likely that the next generation iPhone will come with VoLTE support out of the box, meaning customers can enjoy this new service. Verizon also has plans to launch the service sometime this year.
AT&T claims they will rollout HD Voice and VoLTE on a market-by-market basis. It is available at no additional cost.
Read More [Press Release]