Voice over LTE is the new frontier in voice calling, and it's something we at PCMag don't typically test. Testing company P3 does, though, and rolled out its first major test of VoLTE call quality today. The good news: VoLTE delivers excellent quality calls. The bad news: you're unlikely to hear one right now.
P3 drove around the Washington, D.C. metro area making 7,000 voice calls on the three existing VoLTE networks: AT&T, T-Mobile, and Verizon Wireless. The company found that VoLTE slashed call setup times from around 7 seconds to 2-4 seconds, and it universally improved call quality as well, although more so on AT&T and Verizon than T-Mobile (because T-Mobile has HD calling on its 3G network.)
Charts showed, for instance, that a 3G call on T-Mobile cut off at about 4000Hz, while the VoLTE call kept the voice tones intact up to 7000Hz. Interestingly, according to P3 CEO Dirk Bernhardt, T-Mobile uses a much higher bandwidth voice codec than its competitors (transferring more data per call), which may be designed for better background noise reduction.
Call drop rates were pretty low, and between 0.5 percent and 1.09 percent of calls didn't connect. So the carriers are delivering higher quality calls with similar reliability to their old systems by using VoLTE.
Switching over to VoLTE can also really help the carrier networks, and help you connect to the mobile Internet. As more people use VoLTE, the carriers can switch more spectrum over to more efficient LTE from the older 2G and 3G systems previously used for voice calling, offering more voice and data capacity without adding more airwaves.
Those Calls Don't Connect
Unfortunately, you're unlikely to hear a true VoLTE call soon, because they only work between two VoLTE phones that have both opted in on the same carrier. (That's why we don't test it, as we typically test call quality against land lines so we have a stable benchmark.) VoLTE isn't activated by default even on most phones that support it, and it is, right now, totally not interoperable. If a call needs to be handed to another carrier or a land line, it drops to the lowest common denominator of quality.
That deeply damages the VoLTE experience, and the HD calling experience in general. Verizon and AT&T will only deliver HD voice calling between two VoLTE phones, on the same network, with VoLTE turned on. Right now that's not that many phones. At least T-Mobile and Sprint have some form of HD voice quality to fall back on. But although all four carriers now support HD voice calling to some extent, you can't make an HD voice call between them.
AT&T and Verizon are doing pilot projects connecting their VoLTE system, but everyone's in a trial phase, Bernhardt said.
"I hear it's working, but in the lab. They should really speed that up; all three carriers that launched it, have had really good results," he said.