Among the many the headlines T-Mobile made last week at its Un-carrier event was that its newly acquired iPhone 5 would support HD Voice, a technology that does exactly what its name implies: make calls sound clearer and crisper.
HD Voice, however, is hardly a new technology. Operators have been experimenting with it for some time. Two carriers, T-Mobile and Sprint(s s) have upgraded their networks to support HD calls. Speaking at VentureBeat’s Mobile Summit on Monday, AT&T network SVP Kris Rinne reiterated Ma Bell’s commitment to launching HD Voice over its LTE network later this year. Verizon Wireless(s vz)(s vod) is dallying a bit. It originally planned to launch HD Voice-capable phones on its LTE networks last year, but, according to FierceWireless, Verizon is now targeting the late 2013-early 2014 timeframe.
Given all of that HD Voice activity, why have we heard relatively little about the technology from the carriers apart from the occasional big-splash announcement such as T-Mobile’s? Like so many problems in the mobile industry, the reason for HD’s lackluster momentum is one of interoperability. Even if you own an HD Voice-capable phone on an HD Voice-compatible carrier, chances are you’ve never made an HD-Voice call.
Sprint and T-Mobile are both using different HD-Voice technologies based on the radio standards of their respective network standards, CDMA and GSM. For a detailed explanation, ExtremeTech’s Neal Gompa has written an excellent primer on the differing HD Voice technologies and their inherent limitations. But it basically boils down to this: to make an HD call, you need to meet all of the following stipulations.
- Your phone needs to be HD-capable. Not just HD capable, but support the HD-Voice codec used by your carrier. In the case of T-Mobile, that means the iPhone, the Samsung Galaxy S 3, the HTC One S and probably most newer generation smartphones. For Sprint, that does not include the iPhone because Apple(s aapl) isn’t supporting the CDMA HD-Voice codec, but it does include the HTC Evo 4G.
- The phone you’re calling needs to HD-capable. Not only does the recipient need an HD device, it needs to be running on another HD-compatible network using the same HD technology as your device. Even if a Sprint and a T-Mobile customers both have the right phones, they can’t make HD calls to one another. If either customer called any other carrier or any wireline number, those voice connections also would revert to “standard-definition.” /li>
- Both phones need to be connected to an HD-capable base station. Just because a carrier supports HD-voice doesn’t mean it supports it in all places. Sprint, for instance is enabling it as it upgrades its CDMA systems as part of its Network Vision overhaul (basically everywhere it offers LTE). When Verizon and AT&T launch their voice-over-LTE (VoLTE) services, both caller and recipient will have to be on LTE networks for the conversation to transmit in HD. T-Mobile, however, appears to upgraded its entire network to support HD.
As you can see, that’s a pretty high bar to meet. Consequently carriers aren’t bragging much about their HD-Voice services — very few of their customers can feasibly make an HD call. We’ll start to see more activity as the growing number of iPhone and Galaxy customers on T-Mobile’s network contact one another, but we’ll see the biggest uptick in HD usage when Verizon and AT&T take their VoLTE services live.
Unlike on CDMA, there will be compatibility between VoLTE HD voice technologies and T-Mobile’s GSM-based systems, since they use what is basically the same codec. As T-Mobile and Sprint eventually migrate to VoLTE there will be even greater interoperability.
As my GigaOM Research colleague Colin Gibbs points out voice quality is still an important factor for consumers when deciding on mobile service. It’s difficult, though, for carriers to distinguish themselves competitively with HD-Voice because adoption of the service depends on all carriers offering the technology. That said, HD voice could boost the industry as a whole by making mobile calls more pleasant, rather than the patchy conversations they often are today.