Operators Rally Round IMS for LTE Voice

A group of some of the world's largest mobile operators, equipment suppliers, and device makers have joined forces to fast track a standardized way to deliver voice services over Long Term Evolution (LTE) using the IP Multimedia Subsystem (IMS). (See Telcos Back IMS for LTE Voice.)

The operators involved in the initiative, called One Voice, are AT&T Inc. (NYSE: T), France Telecom SA (NYSE: FTE)'s Orange, Telefónica SA (NYSE: TEF), TeliaSonera AB (Nasdaq: TLSN), Verizon Wireless , and Vodafone Group plc (NYSE: VOD). Two of them, TeliaSonera and Verizon, have ambitious plans to launch commercial LTE services as early as next year. (See Ericsson, Samsung Make LTE Connection, Sweden Claims LTE First, TeliaSonera: We'll Do 4G in 2010, and Verizon: This Is How We'll Do It, and Verizon Wants LTE All at Once.)

The group of operators are joined by Alcatel-Lucent (NYSE: ALU), Ericsson AB (Nasdaq: ERIC), Nokia Siemens Networks , Nokia Corp. (NYSE: NOK), Samsung Electronics Co. Ltd. (Korea: SEC), and Sony Ericsson Mobile Communications . (See AlcaLu Looking to Strike LTE Gold , Spradley: Nokia Siemens Will Be an LTE Leader, and Vendors Vie for LTE Limelight.)

Voice and SMS service delivery is a glaring problem for proto-4G LTE because, as a packet-based network, it does not support legacy circuit-switched traffic. A number of different approaches to this technology conundrum have cropped up, but there is no great consensus among operators about which one is the best way forward. (See Mavenir, Acme Tackle LTE Voice, NSN Goes Solo for LTE Voice, Voice Over LTE & the 'IMS Gap', New Forum Gives Voice to LTE , Voice Over LTE's Future Cloudy, and Mobile VoIP's an 'Unstoppable Train' .)

Faced with a real threat of fragmented approaches for voice-over-LTE service delivery, this initiative is looking to coalesce on a subset of 3rd Generation Partnership Project (3GPP) IMS specifications that will be required to deliver basic voice and SMS services. The group's efforts are expected to bring forward the launch of IMS-based voice-over-LTE services in roughly 12 to 18 months, according to Peter Linder, Ericsson's director for network solutions.

"We looked at what we already defined in 3GPP for multimedia telephony... and agreed on the inevitable subset... for voice and SMS to get that going," says Linder, adding that as a result, IMS-based voice and SMS services can be delivered in 2011, rather than 2012, as is currently envisioned.

Together, the One Voice initiative's members have agreed on a technical profile for voice and SMS service delivery via IMS, which can be accessed here.

This work will be fed back in to the 3GPP. The group aims to start interoperability testing in the first half of next year.

Ericsson's Linder insists that the One Voice initiative is not in response to the Voice over LTE via Generic Access (VoLGA) Forum -- the group that proposes an interim LTE voice concept that tunnels circuit-switched voice traffic through the packet-based LTE network. (See New Specs Deepen LTE Voice Dilemma.)

But the weight of operator support for One Voice makes T-Mobile International AG -- VoLGA's only operator champion -- look increasingly isolated. (See T-Mobile: Voice Discord Threatens LTE and T-Mobile, Orange Open Up on LTE.)

For more details on the technology choices facing operators for voice-over-LTE services, check out the latest Unstrung Insider report, "Voice Over LTE: Many Questions, No Easy Answers."

— Michelle Donegan, European Editor, Unstrung