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Optical/IP

New Specs Deepen LTE Voice Dilemma

A T-Mobile International AG -backed industry group has advanced its efforts to introduce an alternative way to deliver voice services over Long Term Evolution (LTE) networks.

The Voice over LTE via Generic Access (VoLGA) Forum announced today it has published the second version of specifications for its circuit-switch-over-packet approach for voice services over LTE. That means the group is closer to its goal of creating a new set of specifications that will be ready for submission to the 3rd Generation Partnership Project (3GPP) standards body by the end of the year. (See New Forum Gives Voice to LTE .)

But the challenge for VoLGA is to enlist support from more operators -- T-Mobile is the only public operator supporter now -- if it is to succeed in gaining admittance into the 3GPP's body of work.

The VoLGA development is at the heart of a divisive issue for mobile operators as they plan LTE deployments. The problem is that LTE, as an all-IP mobile broadband technology, does not support legacy circuit-switched voice and SMS services, and operators are undecided about the best way to deliver these services. (See T-Mobile: Voice Discord Threatens LTE and T-Mobile, Orange Open Up on LTE.)

Heavy Reading senior analyst Gabriel Brown sums up the dilemma operators face in this column: Voice Over LTE & the 'IMS Gap'.

There are basically three different ways to deliver voice services over LTE:

  • IP Multimedia Subsystem (IMS) is approved by the 3GPP but may be too immature to rely on for early LTE services
  • Circuit-switch (CS) fallback, in which the 2G or 3G networks are relied on for voice services
  • Circuit-switch-over-packet, where the CS voice or SMS traffic is tunneled over LTE
VoLGA is one option for the CS-over-packet approach, along with various proprietary solutions.

In addition to T-Mobile, the VoLGA initiative has the support of all the major infrastructure vendors, with the notable exception of Nokia Networks , which is understood to be developing its own proprietary solution.

The big worry for the industry is that operators will adopt different approaches for voice-over-LTE services, which would threaten the industry's biggest sources of service revenue generation -- voice and SMS.

The VoLGA Forum is developing its specifications in line with 3GPP procedures so that they can be more easily included into the 3GPP process, according to Keith Mumford, director of product marketing, EMEA, at Kineto Wireless Inc. , one of the founding members of the VoLGA Forum and a key supporter of the GAN technology on which VoLGA is based.

"By following the process of the 3GPP, it's easier to slot the specifications into the 3GPP model," says Mumford.

The Forum hopes to have the third stage of the specifications completed before the end of the year so that, with enough industry and operator support, VoLGA can be submitted to the 3GPP for a work item in Release 10 of the standard body's specifications work.

— Michelle Donegan, European Editor, Unstrung

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