Sprint earlier this month announced a service that lets users make and receive unlimited calls at home using any Sprint mobile phone. The service called Airave, is being trialed in selected areas of Denver and Indianapolis, and uses femtocell technology.

A femtocell, also referred to as a home base station, connects mobile phones to a wireline broadband network, providing enhanced in-home wireless coverage. It also offers the carrier a cost advantage because it uses the Internet for low-cost backhaul to the public phone network.

Sprint’s Airave will use a $49 femtocell access point provided by Samsung and unlike some other fixed-mobile solutions that require a dual-mode phone, the service is compatible with any Sprint mobile phone. The service is priced at $15 per month for individuals and $30 per month for families, in addition to the customer's regular wireless voice plan. When callers leave home, their calls are automatically transferred back to Sprint’s mobile network.

Sprint plans to make Airave available later this year to other customers in Denver, Indianapolis and Nashville and to customers nationwide in 2008, according to the company’s announcement.

Unlike T-Mobile’s HotSpot @Home, a Wi-Fi based alternative which can connect to a T-Mobile home base or any T-Mobile hot spots, the unlimited minutes using the Airave device are limited to the customer’s home calling area. But the femtocell can offer better in-building coverage than a public cell site and it solves a problem for some mobile users because it puts the technical equivalent of a personal cell site inside the home. And for users who are considering wireless substitution or VoIP for their current land-line phone, the Sprint solution offers a better price than VoIP and an inexpensive in-home unlimited calling plan for a mobile service. For existing Sprint customers, choosing an Airave service won’t extend their mobile service contract term. And, while targeted to consumers, this fixed-mobile convergence (FMC) could potentially be used by small businesses.

Our analysis: We find it ironic that Sprint and T-Mobile, the third and fourth largest mobile service providers behind AT&T and Verizon are the innovators in FMC alternatives. But we don’t find it surprising that the two larger carriers are dragging their feet on an FMC solution since AT&T and Verizon both have a substantial wireline investment to protect. And we wait with anticipation for enterprise-grade FMC solution using femtocells since they may solve some of the voice over Wi-Fi transmission quality issues associated with Wi-Fi connections.

Steve Taylor is president of Distributed Networking Associates and publisher/editor-in-chief of Webtorials. Larry Hettick is a principal analyst at Current Analysis.