VoLTE Triumphs (if Conditions Are Just Right)

The good news about voice-over-LTE (VoLTE) is that it works as advertised -- crisp, high-quality sound with an instant connection -- but the bad news is a lot of stars have to align to actually experience it.

Independent testing consultancy P3 Communications has completed what it says is the first independent mobile benchmark of VoLTE service in the US via two weeks of intensive testing in April and May spanning 1,300 miles of Washington D.C.

Carriers' own tests have shown strong VoLTE performance, but this is the first to compare the big three operators that have it deployed thus far. Verizon Wireless and T-Mobile US Inc. have nationwide coverage, while AT&T Inc. (NYSE: T) is still in the midst of deploying it market-by-market. Sprint Corp. (NYSE: S) does not yet have VoLTE rolled out, but was included in the study for its legacy voice calling, which fared quite well given that it uses the high-definition codec. (See AT&T Promises More VoLTE Markets in 2015, Verizon to Launch HD VoLTE in 'Coming Weeks' and T-Mobile Beats AT&T, Verizon to VoLTE.)

P3 measured quality, speed and reliability on Samsung Galaxy S5s and found that the quality was significantly improved over legacy voice, especially on AT&T and Verizon, which did not have HD voice on their circuit-switched networks. Average call set-up times also improved to between five and 15 seconds.

Figure 1: Voice Quality in DC POLQA is the ITU-defined voice quality testing technology P3 used to test VoLTE's quality. Source: P3 Communications

Dropped calls were also rare, and P3 CEO Dirk Bernhardt said the engineers only handed off (seamlessly) to a legacy network six times out of a total of more than 2,000 calls made -- five on AT&T, which fell back to 3G, and once on T-Mobile, which, interestingly, fell back to its 2G network even though it had 3G CDMA deployed in DC. Verizon does not offer handoff to CDMA as it can't support eSRVCC. Bernhardt said a few calls were dropped, but overall reliability was "surprisingly good."

"VoLTE is ready for prime time," Bernhardt says. "I tell everyone to try it out. You'll be surprised in the beginning at how different the voice quality is."

Bernhardt thinks it's time for the operators to be more aggressive with deploying it and marketing it to their customers. The problem is, however, while the service does work well, there are still a lot of caveats with VoLTE as it is today in the US. (See VoLTE: So Close You Can Hear It.)

The biggest issue is that VoLTE calls will only work within a single carrier network, and even then, only if both parties have to have VoLTE-capable phones and have it turned on for voice calling. They then also have to be in an area with good LTE coverage. (See Apple Eyes VoLTE as 4G Voice Gets Real and Apple's New iPhones Have 20 LTE Bands, VoLTE.)

If all those conditions are met, they can enjoy the crystal-clear calling. Otherwise, it's plain old legacy voice for them. Also, as we discovered on my interview with Bernhardt, three-way calls fall back to legacy when the third party is added.

For more on 4G voice, visit the VoLTE/rich communications content section
here on Light Reading.

I've had VoLTE switched on my iPhone 6 on Verizon Wireless for the past few months, and have been impressed with the quality when I talk to my husband (who is the only other person I know with VoLTE enabled, but also one of the only people I actually still talk on the phone to...). The call gets connected immediately, and we've both checked to see if we accidentally went on speakerphone because our voices are so amplified -- for better or for worse.

So, while it may improve our communication, it's certainly not the norm. I had to know where to enable it on the device and tell him to do the same. You really have to seek it out, and then you likely won't find many people to talk to, which is why the operators haven't made a bigger deal of it -- at least not yet.

The operators have pledged to work on interoperability this year, which will make a big difference, as will more handsets supporting the technology. Really, there is no downside to using VoLTE as P3 finds its quality is matched by its reliability. Bernhardt says he wouldn't be surprised if the operators made it a default on future releases. (See Verizon, AT&T Plan VoLTE Harmony in 2015 and AT&T's Rinne: Carriers Working on VoLTE Interoperability.)

"For such a young technology, its surprising stable and you can clearly see the benefit of it," Bernhardt said. "I don't see any reason why the operators hide it or do a soft launch. At some point in the next couple of months, I'd be surprised if they don't use it as the default voice service."

— Sarah Thomas, , Editorial Operations Director, Light Reading