The voice over mobile broadband (VoMBB) phenomenon is starting to develop in earnest, with voice over LTE (VoLTE), voice over Wi-Fi (VoWiFi) and even video over LTE (ViLTE) starting to take shape in the form of trials and nascent commercial deployments. Perhaps more interestingly, the re-architecting of voice transmission to run across a native IP infrastructure paves the way for the rollout of further rich communication services (RCS), like video calling, video messaging, conferencing and content-sharing, made available natively as network services rather than as apps.

The move to converge voice and data over LTE and Wi-Fi allows operators to harness the power of long-tail, Internet-based service innovation in a way that keeps the value—and the customer relationship—firmly within the purview of the operator network. For instance, Sprint has implemented VoWiFi, ostensibly to provide better voice coverage and quality in places where its network is spotty, like rural communities or indoors in public places. Home users can leverage their existing Wi-Fi routers—a near-ubiquitous feature of broadband households—to avoid the voice quality issues associated with 2G or 3G calling.

There are over-the-top (OTT) apps that do the same thing, but they require users to download and install a separate app for doing so. In the case of Sprint’s VoWiFi service, users that are connected to a Wi-Fi network can use a phone’s native dialer to make calls as they would normally—but in the background, those calls are being routed over the Wi-Fi access point and the converged broadband network. So for users, it’s seamless.

The value proposition may be better coverage at first, but that ability to offer these kinds of services that heretofore were the purview of third-party apps offers operators a path towards better network monetization via non-commoditized, next-gen services.

“With the VoLTE rollouts, I predict in 2015 that we’ll start to see value-added VoLTE apps follow – you know, VoLTE voice mail, VoLTE IVR services, VoLTE voice texting, and other voice and video centric services that would compete with OTT services,” said Jim Machi, senior vice president of product management and marketing for Dialogic, in a blog.

As an example of this playing out, T-Mobile USA, which deployed VoWiFi last year using a Mavenir Systems platform, claims that it is experiencing fewer customer disconnects from its service, at least in part because of the Wi-Fi calling service.

“In fact as of December 2014, 6.6 million Wi-Fi calling calls were made each day by its customers,” reported research firm Dell’Oro Group. “Our expectation is that offering VoWiFi service may also reduce reliance on services like Facetime, Skype or their alternatives. H3 UK also views Wi-Fi calling to be a differentiator.”

As for the rollout of other RCS services down the line, implementing baseline VoMBB functionality now will allow service agility later. For instance, the guts of the Sprint service are based on Taqua’s Virtual Mobile Core platform, which uses SIP for complete feature transparency for voice, messaging and supplementary services, including single-number service. The seamless user experience is maintained by utilizing the subscriber profiles from the legacy cellular infrastructure.

“It’s technically an RCS service,” said Frederick Reynolds, Taqua’s vice president of marketing. “Though we don’t market that at the main differentiator. But it’s a doorway to future advanced mobile solutions down the road, should they choose to deploy them.”

Rollout Lookout

When it comes to how the pieces of the VoMBB universe fit together, VoLTE addresses convergence on the go, while VoWiFi is more of a home zone and enterprise environment play. The idea is to have both implemented, with the ability eventually, to hand off calls between the two.

While some operators are working on one or the other, Dell’Oro Group believes that the most common deployment plan is to start with VoLTE, then move to VoWiFi.

“In most of these cases, VoLTE services get rolled out first, and then VoWiFi is either offered as a service simultaneously or after some delay,” said researcher Chris Depuy, in a blog. “Very commonly, the same vendors are used for both services – at least on the initial rollout. We believe this is likely to be the most common path chosen by service providers.”

In any event, more VoMBB deployments are on the way. Vodafone UK has confirmed plans to launch both Wi-Fi calling and VoLTE this summer, as part of its $1.2+ billion investment in upgrading its networks. The former is geared toward customers in areas with less-than-stellar cellular coverage or where it’s difficult to get an indoor signal; the VoLTE service will meanwhile simply be a more cost-effective IP replacement for the existing circuit-switched 2G and 3G-based voice calling service—for now.

“It is another important step towards our commitment to build the UK’s strongest converged network,” said Vodafone UK CEO Jeroen Heoncamp.

It won’t be the only game in town for very long: Vodafone UK competitor EE will launch its own Wi-Fi calling service on the Lumia 640 and Samsung Galaxy S6 smartphones next month, with future launches expected to include iPhone 6 and 6 Plus.

In the States, AT&T has slated a VoWiFi launch for later this year. On the VoLTE front, both AT&T and Verizon Wireless have launched VoLTE. And, the two are taking the next step in the evolution of the technology by enabling VoLTE- to-VoLTE connections between Verizon Wireless and AT&T customers. VoLTE interoperability is expected sometime in 2015.

As of last fall, 21 percent of operators were investing in VoLTE deployments, according to the Global Mobile Suppliers Association (GSA), with that figure set to double this year. The proportion of 21 percent of carriers investing in VoLTE translates to 71 in total across 36 countries.

“The pace of introduction [of VoLTE] is accelerating and several more launches are imminent,” said Alan Hadden, president of the GSA. “We have seen a significant uptake in deployments of VoLTE-enabled HD voice services and LTE-Advanced carrier aggregation systems, and these are the major industry trends worldwide.”