BARCELONA -- Mobile World Congress 2015 -- Launches of rich communication services (RCS), the operators' long-discussed answer to WhatsApp, are now imminent in the US, executives from T-Mobile and Mavenir have confirmed this week.

The GSM Association (GSMA) -supported technology that brings services such as video calling, presence, group chats and file sharing native to the device has seen a lot of false starts and hype, but it's finally going to happen in the US in 2015. T-Mobile US Inc. Vice President of Engineering and Quality Assurance Grant Castle told Light Reading last week that the carrier would be launching RCS in the near future, and Mavenir Systems Inc. President and CEO Pardeep Kohli confirmed today that other big operators would follow suite. (See Q&A: The Castle in T-Mobile's LTE Network and T-Mobile Plans Small Cells as Niche Play.)

"RCS is soon, very soon," Castle told Light Reading in a pre-show interview. "VoLTE was the baseline on that and was the most difficult. We worked hard to move it forward. We're taking those learnings for RCS and video calling and similar services."

Mavenir's Kohli lent weight to those comments, telling reporters today that all of the big four would be launching RCS this year. His company, which Mitel Networks Corp. announced it was acquiring on Monday, provides RCS, voice-over-LTE (VoLTE), voice-over-WiFi (VoWiFi) and session border controllers (SBCs) for wireless operators. It powers VoLTE and messaging for T-Mobile, messaging for AT&T Inc. (NYSE: T) and "some apps" that Kohli wouldn't disclose for Verizon Wireless and Sprint Corp. (NYSE: S). (See Mitel to Acquire Mavenir for $560M.)

"Everyone is ready now; devices just need to get ready," Kohli said.

Most Android devices, including Samsung Corp. 's Galaxy S6, are compatible today, but the one big elephant in the room, Apple Inc. (Nasdaq: AAPL), does not yet support it in the iPhone. He expects Apple to come around soon, but stressed he doesn't have insider info on the Cupertino giant's plans. (See Samsung Dials Up RCS for VoLTE.)

When the operators do launch RCS, Kohli said the services would all be tied to a user's phone numbers, unlike Sprint's current iteration of RCS via a preloaded Jibe Mobile app. But, he said, don't expect the services to work across carriers. They will be siloed at first, like VoLTE. Once operators work out IP peering agreements -- something the optimistic CEO also expects to happen this year -- RCS interoperability will follow. (See Sprint Jibes With OTT Comms and AT&T LTE Roams to 13 More Countries.)

Interoperability is something others are working towards too, including Jibe Mobile, which announced more operators participating in its Hub interconnection service at MWC this year. (See Jibe Hub, Fring Alliance & More RCS Action at MWC and Deutsche Telekom Outlines Its RCS Evolution .)

For more on operator's RCS strategies, check out the VoLTE/rich communications content channel here on Light Reading.

In other "it's going to happen this year" news from Mavenir, Kohli said the company will announce its first cable customer for VoWiFi in 2015. He wouldn't say which one, but he did call out Comcast as having talked about doing VoWiFi and noted that Cablevision Systems Corp. (NYSE: CVC), which offers the Freewheel WiFi service, is not a current customer. (See Mavenir Launches VoWiFi for Cable, Comcast Weighs WiFi Plans and Cablevision's New WiFi Try – Freewheeling Enough?)

He also touched on the Mitel acquisition in the press Q&A, which sounds like much more of an expansion play for Mitel than an acquisition that yields a lot of synergies. Mitel serves the enterprise market, while Mavenir is squarely focused on service providers. For Mavenir, Kohli said the deal will help it scale globally and compete against the likes of Nokia Corp. (NYSE: NOK) and Ericsson AB (Nasdaq: ERIC), but he does think there are opportunities to bring Mitel's unified communications capabilities to mobile phones.

"We'll be able to synergize on a number of things that happened in the enterprise 10 year ago but haven't happened on phones yet," he said. "There's no reason these functions can't come native in the phone."

 Sarah Thomas, , Editorial Operations Director, Light Reading