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Mobile industry decides on LTE voice standard

LTE, the successor to 3G, will use a technology based on the IP Multimedia Subsystem (IMS) framework to carry voice and text messages
Written by David Meyer, Contributor

Mobile operators and telecoms equipment manufacturers from around the world have agreed on how to carry text messages and voice calls over LTE, the planned successor to 3G.

The long-term evolution (LTE) of 3G will involve IP-only networks, unlike the circuit-switched networks that currently support mobile voice calls and text messages. A group of companies said on Wednesday that they will use a technical profile called One Voice, based on the IP Multimedia Subsystem (IMS) framework, to support such services on their next-generation networks.

The companies involved in the One Voice initiative are AT&T, Orange, Telefonica, TeliaSonera, Verizon, Vodafone, Alcatel-Lucent, Ericsson, Nokia Siemens Networks, Nokia, Samsung and Sony Ericsson.

IMS is a framework that is intended to converge data, speech and network technology into a single platform. As IMS can simultaneously serve fixed broadband and LTE wireless services, the use of One Voice will also "open the path to service convergence", the companies said in a statement.

"By following the jointly 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," the statement read. "The objective of the initiative is to ensure the widest possible ecosystem for LTE and to avoid fragmentation of technical solutions."

Once the One Voice profile has been finalised, it will be handed over to existing industry forums, according to the statement.

IMS is not the only solution to the problem of carrying voice and text messages over LTE, and two alternative techniques had been proposed. One was to fall back to the circuit-switched network for voice and text (CS-fallback), which is seen within the industry as a temporary measure. The other was a proprietary system, backed by T-Mobile and others, called Voice over LTE via Generic Access (VoLGA). VoLGA involved feeding existing voice and text services into LTE's IP-centric system.

Steve Shaw of Kineto Wireless, a VoLGA backer, said that his company was fully supportive of One Voice, as it is needed to save IMS telephony — a system that many in the industry have been trying to push for years.

"The plan of record for many operators, and the ultimate goal in the industry, has always been IMS telephony," Shaw wrote in an email to ZDNet UK. "What One Voice seeks to do is simplify and clarify basic IMS telephony specs. By their own admission, IMS has become so complex and unwieldy that it was impossible to find a starting point."

Shaw argued that One Voice does not remove the need for an interim solution, particularly for those operators that are not ready to invest the money needed to roll out an IMS-based network. In this case, CS fallback would be a step back from IMS and a move in completely the wrong direction, according to Shaw. "VoLGA has always billed itself as the best path to IMS," he said.

However, while One Voice is a "good first step" towards IMS telephony, it's still many years away, he noted.

Telecoms analyst Dean Bubley, of Disruptive Analysis, said that the One Voice initiative "won't make any difference to operators who are IMS-sceptics." Nevertheless, it does help clarify and standardise the IMS voice proposition, he believes.

"[The initiative is] driven by the urgent needs of some early LTE deployments, largely by IMS-enthusiastic operators, specifically Verizon Wireless in the US and TeliaSonera," Bubley wrote in an email to ZDNet UK.

He noted that Vodafone was involved in the initiative, despite having recently announced Vodafone 360, a non-IMS application suite. "But then, it seems likely that full rollout of LTE by Vodafone is still some way off anyway," Bubley wrote, adding that One Voice implied a recognition by the industry that the CS-fallback option is undesirable.

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