LTE may be data-only, but still needs to support voice

There is an interesting situation that is brewing when it comes to Long Term Evolution (LTE) technology, and I’m surprised to find people already talking about it as operators aren’t scheduled to deploy the technology until next year. And that is: How will LTE support SMS and voice, which are the bread and butter of the mobile operator business today? Right now, LTE cannot support either because it is an all-IP technology that doesn’t support the circuit-switched architectures found in today’s mobile networks.

It’s easy to say that voice and SMS aren’t all that necessary in an LTE world since the technology is a data-only play. But Steve Shaw, vice president of corporate marketing with Kineto Wireless, which offers software for wireless broadband services, says SMS functionality is important for LTE because the early LTE dongle service that mobile operators, and potentially some public-safety agencies, will have at their disposal will not work without SMS functionality. Mobile networks, including LTE networks, are constructed to rely on SMS for device-configuration messages.

In a similar vein, T-Mobile in Germany — which so far doesn’t have any spectrum to deploy the technology — nevertheless has said voice and SMS need to be supported in the LTE world. But that only makes sense if an operator is deploying LTE to gain the greatest spectral efficiency possible, but then falling back on less spectrally efficient 3G networks to handle voice. There’s also a chicken-and-egg problem: Manufacturers won’t make LTE phones if voice services aren’t enabled on the network. Sexy devices are what sell such services going forward, not boring dongles.

So what does this have to do with public safety? The Association of Public-Safety Communications Officials, the National Emergency Number Association and the National Public-Safety Telecommunications Council (NPSTC) endorsed LTE last month. Moreover, eight public-safety groups have said they want Congress to allocate the 10 MHz of commercial D Block spectrum in the 700 MHz band for public-safety use. Deploying an LTE network will be an expensive proposition for sure, so why wouldn’t the public-safety sector want to leverage such networks to the fullest extent possible? If these networks deliver on the efficiencies the technology promises, why wouldn’t government agencies want to cram as many types of communications as possible on these networks?

Some wonder whether LTE eventually will become a major conduit for public-safety voice communications. It may not replace two-way radios, but it could serve as a valuable complement and perhaps replace many of the commercial services that the public-safety sector uses today to augment its emergency communications services.

As it stands now, the industry has a few directions in which it can move to solve the SMS and voice-over-LTE problem. The 3G Partnership Project (3GPP), in charge of creating LTE standards, has endorsed the use of IP Multimedia Subsystem (IMS) architecture. On a basic level, IMS replaces an operator’s back-end network architecture with an all IP-based system, making it easy to deploy services like SMS and voice via a VoIP-type service. But IMS has been talked about for many years with little movement in the space, so it’s still considered an immature and expensive approach.

Others have talked about enabling a circuit-switched fallback capability whereby the mobile device is forced off the LTE network onto 2G and 3G networks for voice and SMS capabilities. That approach would be inefficient, however, and certainly not something the public-safety sector could support without becoming beholden to mobile operators.

And finally, the last solution seems to be the most promising in the near term. T-Mobile International and major handset and equipment vendors have joined forces to promote what they call Voice over LTE via Generic Access (VoLGA). By September, the group hopes to hammer out a common set of standards to allow circuit-switched SMS and voice traffic to travel over LTE using a generic-access approach. Some of the wireless industry’s biggest vendors are founding members of the group, including Alcatel-Lucent, Ericsson, Huawei, LG Electronics, Motorola, Samsung, Starent and ZTE.

Shaw said there is no reason that operators can’t migrate that functionality to IMS down the road, but the issue may come down to operators and their perceptions of IMS. Is it really that far behind in their view? Or do they need a bridge like VoLGA? Some point out that without solving the SMS and voice-over-LTE problem now, LTE deployments could be delayed or struggle coming out of the gate.

I don’t believe the voice-over-LTE issues will become a deal-breaker for LTE deployments, but how they are handled by the commercial industry could have both a technical and cost consequence on the public-safety sector.

What do you think? Tell us in the comment box below.