Tipping Point or Longer Slog for HD Voice?

By Doug Mohney
Contributing Editor

Rich Tehrani (News - Alert) asked me an interesting question today: Is HD voice mainstream?  The answer is, "No, but..." for a number of different reasons.   Clearly, there have been great strides in introducing HD voice on mobile networks.  But there's a lot of work to be done to make the experience seamless and to encompass the full range of "phone" experiences.

Out of the four major U.S. mobile carriers, the smaller two either have or are in the process of deploying HD voice. T-Mobile (News - Alert) US,  bless John Legare's pirate heart, has had HD voice up and running on its network since January 2013.  After various fits and starts, Sprint has said it will offer national HD voice coverage on its upgraded CDMA network by mid-year; the carrier is already offering HD voice in select markets.

AT&T and Verizon (News - Alert) made noises about deploying HD voice as a part of Voice over LTE (VoLTE) throughout 2013, but now the drumbeat has shifted to when and where in 2014.  An Engadget piece today says AT&T (News - Alert) will start deploying VoLTE later this month -- May 2014 -- in Chicago and Minneapolis, assuming market trials don't blow up.

Poor Verizon, first to toot the VoLTE horn, is only repeating that it will have service out sometime in 2014.  Credit Suisse is betting it will happen in the second half of 2014, which would be another yet another pushback from Verizon.  The company has been making noises about VoLTE launches for the past four years, with windows sprinkled throughout 2012, 2013, and 2014.

Taking all of this into account, maybe, perhaps, possibly all four U.S. cellular carriers will have HD voice running by the end of 2014.  But there's been no public discussion as to how and when carriers will exchange HD voice calls among networks, and that's where some headaches come in. AT&T and Verizon should be able to move HD voice between their LTE (News - Alert) networks in a relatively simple fashion, assuming they agree to peer (exchange traffic) as equals.  It's the same network tech, it's all IP, there's no futzing around with converting codecs or different network types.

Exchanging calls with T-Mobile gets to be a bit more interesting, but not really difficult.  Calls made on T-Mobile's network would have to be converted/routed via IP to AT&T and Verizon, but nobody should break a sweat.  Both T-Mobile's GSM-based network and VoLTE use AMR-WB as the standard HD voice codec (encoding scheme), so you don't have to worry about transcoding (translation).  T-Mobile will also have VoLTE down the road, so it will make life easier for everyone.

And then there's Sprint. The company has said very little about whether it may or may not move HD voice calls from its CDMA network to other carrier networks, but the two issues involved include converting calls from CDMA to (presumably) an IP format on the network level and then transcoding between the EVRC-NW codec used on Sprint's network and AMR-WB used by everyone else on the planet when it comes to HD voice.

Ultimately,  Sprint will have to transcode between AMR-WB and EVRC-NW because it is going to run VoLTE on its LTE network.  The alternative is to drop down HD voice calls between the networks to narrowband and that would result in unhappy customers who don't want to worry about who is on what network when they are making an HD voice call.

Needless to say, there's a lot of work to be done before HD voice calls are seamless between cellular carriers.  And that's not even considering the ability to move calls between cellular and broadband worlds.  HD voice is moving to a tipping point, Rich, but I'm not ready to go mainstream yet.  Ask me again in about a year.