There's speculation T-Mobile USA is quietly rolling out HD voice on its network. In combination with the company's recent announcement it will be able to sell "Apple products" -- i.e. the iPhone 5 -- it would give the mobile carrier a significant leg up over Sprint in rapidly bringing HD voice to the U.S.

DSLreports.com  says it has seen "signs" of AMR-WB codec deployment into T-Mobile's network, based on information from the Samsung Galaxy S III engineering mode, in the "ServiceMode" menu. The AMR-WB codec shows up as the codec selected by the phone for a network call, meaning T-Mobile is quietly adding AMR-WB to its existing HSPA network as a software upgrade. 


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Adding HD voice support would fit into T-Mobile USA's strategy of offering unique and better features than incumbent carriers. It would also dovetail nicely with T-Mobile's announcement last week of a deal with Apple, with products coming in 2013. Exactly when in 2013 is unclear, but analysts predict T-Mobile USA could move nearly five million iPhones in the first year of sales.  

T-Mobile USA's HSPA network has been long able to support AMR-WB, according to industry insiders, with the major issue in rolling out HD voice being a software upgrade and the appropriate marketing support to differentiate call quality from the rest of the pack. No new hardware is necessary in the core network and nearly all new model Android and Windows phones support the AMR-WB codec.

Sprint had initially vowed HD voice would come as a part of its CDMA 1X Advanced upgrades later this year, but the company has backed off on its promotion of the technology. In addition, Apple isn't currently providing HD voice support on 1X Advanced for the iPhone 5, leaving Sprint in the embarrassing position of having to say it didn't support the feature available "at this time" at the product's launch.

Voice over LTE (VoLTE) also seems to be further down the road for Sprint, with late 2013 or 2014 appearing to be the most likely date for service turn-up. The VoLTE standard lists AMR-WB as its default codec, so if the carrier is running VoLTE to standard -- something MetroPCS didn't do when it rolled out its voice service over LTE -- you get HD voice.

AT&T also has the network assets and technology to introduce HD voice on its HSPA network if it chooses to do so. So far, it has not, but talk from Sprint and rumblings from T-Mobile USA may stimulate it to add higher-quality voice to its existing service offering.