The Voice Call Continuity specification of the IP multimedia subsystem standard eventually will allow seamless handoffs of voice calls to support fixed/mobile convergence, or FMC, services. But VCC may not be widely implemented in networks and handsets for the next few years.

For now, there are other methods for providing roaming between mobile and fixed Wi-Fi networks. Unlicensed Mobile Access (UMA) may be the most viable technology right now, and the most popular among service providers, including members of the Fixed-Mobile Convergence Alliance (see textbox), but UMA also can't seem to shake the critics that have hounded it nearly since its inception.

Kineto Wireless, the vendor that pioneered UMA with the development of the first UMA network controller, announced last month that the technology has been picked up by five major service providers thus far. BT was among the first to do so last year, and the U.K. carrier recently launched commercial service based on UMA. More recently, Telecom Italia CEO Riccardo Ruggiero told Italian publication La Repubblica that the carrier is planning to launch a FMC)service as early as this month. The service, called Unico, will use UMA.

Meanwhile, Orange is working toward launching its previously announced UMA-based roaming service, and corporate parent France Telecom also has announced plans to launch an FMC service in the fourth quarter of this year — though it hasn't formally specified UMA technology as the basis for it.

Yet, UMA detractors are still nipping at the heels of the technology. Radioframe Networks is a Bellevue, Wash.-based company that offers pico cell base stations for indoor deployment. President and CEO Jeff Brown, speaking with Telephony's Wireless Review at the recent Wireless 2006 trade show, described his company's approach to indoor wireless coverage as being “like a licensed version of UMA. It keeps the customer in the licensed band. With UMA, you have to manage service in an unlicensed band and you have to get customers to buy a new handset. And how are you going to do customer service for it? It's an interesting technology but I think there are some issues that won't allow it to be ubiquitous.”

Hakan Eriksson, chief technology officer and senior vice president and general manager of research and development at Ericsson, also said at Wireless 2006 that UMA has limited utility in advance of IMS. “UMA is more a solution for a bad coverage area, where you have no other way of extending coverage for the customer,” he said. “And as a user, you have to buy another expensive phone. It's very complex.”

Still, while landing more carrier support, UMA also is luring more support from handset-makers. LG and Samsung already have Kineto's client software in their handsets, and Motorola is listed as a Kineto partner. Also, while critics kept the heat on UMA at Wireless 2006, Kineto went on to win the Wireless Emerging Technologies Award at the same show. The uphill battle continues, but for now, UMA seems game.