There's been a lot of talk over the past few months about fixed-mobile convergence, but at least one analyst firm estimates it will take many years and a lot of cooperation between carriers and vendors to make seamless continuity across fixed and mobile networks a reality.

According to the Yankee Group, wireless is chiseling away at the wireline market through local and long-distance minutes, and that soon will be joined by broadband when customers start to substitute 1XEV-DO service and HSDPA data services for WLAN hot spot use and home DSL and cable modem access.

However, according to Yankee Group analyst Keith Mallison, achieving fixed-mobile network convergence will require three things from wireline and wireless operators in order to succeed.

First, carriers must offer stand-alone service integrity. This means that convergent services must first work adequately on an intra-network basis before being extended to other devices and networks. As an example, Mallison points to MMS. One technology vendor estimates that more than 15 percent of all MMS messages don't even leave the device because of configuration issues. Applications need to be able to span many devices and multiple networks.

Second, Mallison says standards must have conformity across networks and carriers. Although standards such as Simple Mail Transfer Protocol enable e-mail messages to be sent and received over various networks, more sophisticated applications such as content-based charging is nearly impossible across networks.

Third, carriers must unite their organizations across wireless and wireline networks.  Mallison says that most carriers are still divided with wireline, unlicensed wireless and cellular under separate ownership or management. High-level service continuity will only be possible when a single CTO organization conceives and deploys converged network architectures, Mallison says.

The analyst's comments come as more than a dozen companies have come together to publish a set of open specifications for extending mobile voice and data services over WLANs. Companies that participated in the development of the Unlicensed Mobile Access (UMA) specifications include Alcatel, AT&T Wireless Services, BT PLC, Cingular Wireless, Ericsson, Kineto Wireless, Motorola, Nokia, Nortel Networks, O2, Rogers Wireless, Siemens, Sony Ericsson and T-Mobile USA.