When will we see voice over LTE?

It was time for operators to say something about how voice and SMS will be supported on LTE networks. AT&T, Verizon, Orange, Telefonica, Vodafone and TeliaSonera came out in support of using IP Multimedia Subsystem (IMS) for LTE, which can't support voice or SMS because it's a packet network. They needed to cast their support as the space was headed for fragmentation with various methods being proposed as to how to accomplish this. T-Mobile International has been the most vocal, supporting voice over LTE via generic access or VoLGA. (See the story below.)

While vendors say an IMS solution can be ready within 12 months, that still doesn't mean Verizon will be offering voice over LTE shortly after it rolls out LTE. It may be some time before voice is running over LTE given the sluggish rollout of IMS and the uncertainty around quality of IP voice over wireless networks. Voice quality must match that of the 2G experience before an operator like Verizon is willing to migrate that valuable traffic. Godfrey Chua, research manager-wireless and mobile infrastructure at IDC, recently told FierceWireless that Verizon fully expects its 2G CDMA network to support voice until 2020 [1].

Of course, the lack of maturity of IMS, which has been the plan all along for supporting voice over LTE, is exactly why T-Mobile International and other vendors supported VoLGA from the get-go. Alcatel-Lucent and Ericsson, which have supported VoLGA, aren't abandoning that effort either. T-Mobile reasons that since LTE is supposed to give operators the most spectrally efficient networks, it only makes sense to put all traffic on that network and not rely on less efficient 3G networks. T-Mobile, interestingly, has not made any commitments to LTE given its lack of spectrum to do so. VoLGA supporters say there is no reason that operators can't use VoLGA now, and then migrate SMS and voice functionality to IMS down the road. But some analysts caution that making that interim step might create more complexity for network operators.

What's more important to operators like Verizon and TeliaSonera, which will be the first in the world to launch commercial LTE services, is not so much having SMS and voice from the get-go, but making sure handset developers are coalescing around one standard. The last thing operators need is fragmentation in the device space. Nor do they want handset makers to be sidetracked by VoLGA. The question is now, is the VoLGA initiative dead?--Lynnette [2]