AT&T commercially launched its first IP multimedia subsystem application at NXTcomm, revealing that it is offering its video sharing service in three U.S. markets this month and plans to expand the platform across its national 3G network by the end of July and eventually to across its broadband and TV networks.

AT&T first unveiled the application in March, but today it offered an up-close look of the client and its pricing plans. Video Share won’t be cheap. It will run 35 cents a minute a la carte or be sold in bundled minute plans ranging from $5 to $10 a month for 25 to 60 minutes of use, specifically. The session initiation protocol (SIP)-based client communicates back to a SIP application’s server in the IMS core each time a call is placed. If the receiving phone is a 3G-video-capable device, the caller’s phone will display a softkey, allowing him or her to launch the video capability—essentially streaming whatever enters the phone’s camera lens to the contacted person’s screen.

The service is only available over UMTS/HSDPA phones because the technology is the only one that can support simultaneous voice and data transmission. While the HSDPA network is used for the voice transmission, the voice component is a regular circuit-switched call. That makes Video Share AT&T’s first 3G-specific technology not available over its legacy GPRS/EDGE networks. It’s also the first time AT&T has put a full SIP-stack into the phone, which could serve not only as a blueprint for future IMS services but will allow AT&T to integrate Video Share back into AT&T’s wireline network, said Ellen Robertson, director of consumer data marketing for AT&T Mobility.

“This lays the groundwork for AT&T’s three-screen strategy,” Robertson said. “Today video share is mobile-to-mobile. … Within the next year you’ll see us make progress in bringing this to the PC and to the TV.”