T-Mobile Moves Beyond HDVoice

T-Mobile Nexus5 EVSI’ve been a T-Mobile customer for a long time. In fact, my transition to T-Mobile happened when I bought my first smart phone, a Blackberry 8100 (aka Pearl).

More recently I’ve been using an LG-made Nexus 5. No, not the newer 5X. Late last year I semi-regressed from a One+ One to a Nexus 5. One of the reasons for that step backward in time was to finally be able to enjoy mobile HDVoice calls to my wife, who also carries a Nexus 5.

T-Mobile, who lead the US in the rollout of mobile HDVoice, supports it’s use for in-network calls between a list of supported handsets, including the Nexus 5. That initial rollout of HDVoice came before the big build of their LTE network. They enabled the AMR-WB codec (aka G.722.2) over their existing 3G HSPA+ network.

Most other US carriers waited until their LTE rollout to launch HDVoice. An LTE network is natively an IP network, readily supporting advanced voice codecs and video. When the voice calls are handled over the LTE network it’s called Voice-Over-LTE or VoLTE, which is very different from how voice was handled on 3G networks.

Recently T-Mobile issued another press release announcing their next step in improved call quality; VOLTE Enhanced Voice Services or EVS. In the release they make three basic claims:

  1. First, EVS improves voice call reliability in areas of weaker signal, which means the rare dropped call on LTE will happen even less frequently.
  2. Second, EVS provides even higher-fidelity calls than the HD Voice we were the very first in the US to introduce back in 2013. EVS does this with a broader audio frequency range, which translates to richer, more realistic-sounding voice audio.
  3. Third, EVS delivers all this more of the time and in more places. EVS works whether you’re on Wi-Fi or the T-Mobile LTE network.

All of these things make sense.

EVS has a number of operating modes, supporting Super-wideband and Fullband. These are beyond mere "wideband" HDVoice as represented by AMR-WB, although it’s unclear which modes T-Mobile has enabled.

According to VoiceAge, who licenses an EVS implementation, EVS delivers better quality for both voice and music at bit rates comparable to traditional AMR-WB. Further, it has a mode that allows it to interoperate with AMR-NB and AMR-WB, while delivering improved packet loss concealment. The last point possibly explains the following claim made by T-Mobile.

"And the bonus? Our patent-pending deployment of EVS benefits T-Mobile customers with compatible phones even if the person on the other end of the line doesn’t have an EVS-capable device. That’s right, even if you call another non-HD network, you’ll benefit from the enhanced voice experience."

Of course, the carrier gets to decide what capabilities are supported on specific handsets. T-Mobile is supporting EVS on the LG G5 and Samsung Galaxy S7 and S7 edge, after an OTA software update. They plan to offer 7 EVS-capable smartphones by the end of the year.

If there’s an EVS-capable Nexus offering that isn’t gargantuan in either dimensions or price it might it well into my future. It must fit into both my budget and my pocket.