with IMS, VoLGA and CS fallback vying for top spot.
LTE is noted for its speed, simplicity and elegance. It can support stunning data rates and has the potential to revolutionize telecommunications with a host of innovative, high-bandwidth applications.
But for all of the promise inherent in its blazing speeds, LTE still has to figure out how to handle the industry’s cash cow: voice. In its current form, LTE cannot support SMS and voice services based on circuit-switch technology.
“There are concerns regarding how to deliver voice and SMS over LTE [because] voice is the primary source of sales accounting for an average of about 75 percent of wireless services revenue,” says ABI Research analyst Nadine Manjaro.
LTE is designed as an IP-only technology and is not designed to carry voice. It has to use an overlaid voice solution, and despite the technology’s rapidly approaching worldwide deployments, the industry has yet to settle on a single voice-over-LTE technology.
An ideal solution will create a standard for voice over LTE that will be implemented by the vast majority of operators, thereby ensuring roaming and service continuity across networks, Manjaro says. “One common solution is needed to fit all LTE operators.”
The main problem is discovering what that solution will be.
The most prominent voice over LTE technologies are an assortment of interesting acronyms: IMS, CS fallback, VoLGA. Each technology has its benefits and big-name benefactors, and if the industry decides to standardize voice-over-LTE, a lot of haggling probably will occur first.
CS (circuit switch) fallback leverages circuit switched networks and third-generation networks to deliver voice over LTE. So far, the technology has only one key backer: Verizon Wireless, which will use its CDMA 2000 1XRTT network to handle voice while it moves its EV-DO customers to LTE. Verizon likely will continue on that path for the next few years, although most W-CDMA operators are using GSM as a near-term voice solution that will eventually be used for CS fallback.
As the nation’s largest carrier, Verizon wields a tremendous amount of influence. For instance, when it chose LTE over WiMAX, the industry quit most of its bickering over the matter and declared LTE as the clear winner. When it comes to voice over LTE technology, however, it’s unclear whether Verizon has any clout: So far, Verizon hasn’t secured any big-name backers for CS fallback.
In contrast, IMS and VoLGA both have industry bigwigs standing behind them. IMS is supported by the 3GPP standards body that developed LTE, in part because it can enable VoIP on LTE if operators already have the technology deployed on their 3G network. ABI’s Manjaro says VoIP on LTE is a great solution for carriers with IMS, describing it as “probably the ideal solution except for those operators who do not have IMS deployed in the network.”
But not all carriers have IMS deployed on their 3G networks. Despite the technology’s backing from the 3GPP standards body, IMS has not garnered more significant supporters and the rollout of the technology has been sluggish.
IMS also faces a major challenge from VoLGA, which tunnels circuit switched voice traffic across LTE from the generic access network controller (GANC) server to the evolved packet core in LTE.
The peculiar acronym, which stands for voice over LTE via generic access, has proved to be a disruptive new entrant to the space. VoLGA was formally launched this spring with the backing of major LTE vendors, including Alcatel-Lucent, Ericsson, HTC, Huawei, ZTE, LG, Motorola and Samsung.
Although IMS is the preferred architecture of future next-generation networks, Yankee Group analyst Brian Partridge says the pragmatics of deployment are forcing LTE infrastructure manufacturers to get behind VoLGA.
“Those bigwigs would love for it to be IMS out of the box, but that’s just not reality. VoLGA is the second best solution… I see it as being the most viable way forward that doesn’t require a re-architecture of the network,” Partridge says. “It’s a very low cost method of getting voice and SMS – the two highest drivers of revenue – onto the LTE network.”
He also dismisses skepticism of VoLGA’s viability that has arisen from the fact that T-Mobile International is currently the only carrier in support of the technology.
“The reason you haven’t seen a lot of operators is because they haven’t studied it yet,” he says. “The learning, the protocol, lack of disruption and sheer number of vendors points to me that VoLGA is the solution.”
Aside from these high-profile contenders, multiple other voice over LTE technologies exist with smaller bases of support. For instance, Nokia Siemens Networks uses a “soft switch” approach, which lets operators use existing mobile soft switch along with Nokia Siemens’ VoIP server. Although this method has the benefit of allowing carriers to reuse existing equipment while migrating to an IMS-based technology supported by 3GPP, it has yet to attract big-name backers.
VoLGA: Voice over LTE via Generic Access
Voice over LTE via generic access (VoLGA) is backed by many industry heavyweights, but it is just one of the solutions
competing to deliver voice over LTE.
MOVING FORWARD, SLUGGISHLY
The industry is far from agreeing on a solution. IMS is supported by the LTE standards body; VoLGA has the backing of industry heavyweights; and Verizon is stubbornly sticking by CS fallback.
“The quick answer to this is that none of them are going to win and all of them are going to win,” says Michael Khalilian, the chairman of the IMS/NGN Forum, a global nonprofit industry association for the advancement of IP Multimedia Subsystem applications and services interoperability. “The bottom line is the content and the content delivery architecture.”
Khalilian expects the deployment of voice over LTE technologies to be “conservative” as operators try to maximize the technology and infrastructure they currently have instead of moving aggressively toward a new solution, a hesitancy which has partially resulted because of the ongoing economic crisis.
Because carriers can depend on their legacy networks to carry circuit-switched voice and SMS, Khalilian says the companies just don’t see the case for rushing toward voice-over-LTE. “Operators are not going to change and it’s hard to justify the technology,” Khalilian says. “The new technology, the business plan and the return on investment all need to be in parallel.”
Analysts Manjaro and Partridge largely agree with Khalilian. After all, the early LTE deployments are going to be about data, not voice, and that gives operators some time. “The handset part of the equation, which is really when you start talking about voice, is a couple years away,” Partridge says.
Manjaro agrees, adding that operators will move ahead with LTE whether or not the industry agrees on a single standard for voice over LTE.
Even if the industry never comes to a consensus, individual operators likely will choose whatever solution fits best for them. If conflicting technologies are used to carry voice on 4G networks, there may be difficulties with roaming, but that’s not a substantial impediment to deployment of LTE.
Because settling on a single technology for handling voice over LTE is more of a convenience than a necessity, it’s not clear that operators are in any hurry to figure out the issue any time soon. For now, they can manage with the technology they currently have in place, leaving IMS, CS fallback and VoLGA in the balance.
Filed Under: Infrastructure