The thorny issue of how to best deliver voice and SMS services over future LTE networks has taken a new twist with news that a group of some of the world’s largest operators and vendors have backed an IMS-based approach to the challenge. AT&T, Orange, Telefonica, TeliaSonera, Verizon, Vodafone, Alcatel-Lucent, Ericsson, Nokia Siemens Networks, Nokia, Samsung and Sony Ericsson have jointly developed a technical profile for LTE voice and SMS services, also known as the ‘One Voice’ initiative. In a joint statement, the companies proclaim that “by following the defined technical profile, the industry can help guarantee international roaming and interoperability for LTE voice and SMS services, ensuring subscribers continuity of these vital services – all while offering service providers a smooth and well-defined path to LTE.” An Ericsson representative told Unstrung that the group’s efforts are expected to bring forward the launch of IMS-based voice-over-LTE services in roughly 12 to 18 months. The work will reportedly be fed back in to the 3rd Generation Partnership Project (3GPP) and the group aims to start interoperability testing in the first half of next year.

Such high-profile support of this IMS-based approach is significant as various technology options are available to operators. Until now, the most prolific option has been the circuit-switch-over-packet approach, promoted by the VoLGA (Voice over LTE via Generic Access) Forum. The VoLGA Forum has secured the backing of Alcatel-Lucent, Huawei, LG, Motorola, Nortel, Samsung and ZTE, but has only one operator on board, T-Mobile. Nokia Siemens Networks, a supporter of the One Voice initiative, has previously proposed its own approach, which it calls Fast Track Voice over LTE.