T-Mobile Ventures invests in Ubiquisys, while T-Mobile USA pushes ahead with Wi-Fi, but the common protocol used by both approaches could link the networks together

T-Mobile Ventures announced it invested an undisclosed amount into UK femtocell maker Ubiquisys and intends to begin trying out the home base station market in the UK, Germany and the Netherlands this year. But on the other side of the Atlantic, T-Mobile USA has been fixated on a competing fixed-mobile convergence implementation, using home Wi-Fi networks to offload cellular traffic.

The strategies of Deutsche Telekom’s European and American arms appear to be completely at odds—at least at first glance. But on closer inspection the two technologies could be entirely complimentary. The glue that could bind them together is the protocol that links both Ubiquisys femtocells and T-Mobile Hotspot@Home routers back to the core network: Unlicensed Mobile Access or UMA.

In a Wi-Fi solution, voice traffic is backhauled to the carrier’s core network over a home broadband connection, and in the case of GSM networks, UMA has become the standard protocol used to tunnel those conversations over the public Internet. A femtocell solution does away with dual-mode phone, transmitting and receiving using the handset’s standard cellular frequencies, but it still needs to tunnel that GSM traffic over the Internet to the carrier core. UMA advocates have been pushing for their pet protocol to perform that linkage for femtocell networks. Last week, the Third Generation Partnership Project included UMA among the possible FMC protocols for both dual-mode and femtocell deployments, opening the doors for dual-platform networks.

While there are still several protocols a femtocell network could implement, Ubiquisys has come down firmly on the side of UMA, which would give T-Mobile’s European and US operations a common network platform. For T-Mobile USA, the same Kineto Wireless-powered UMA gateways that power its dual-mode service conceivably could be used for an Ubiquisys femtocell launch. If T-Mobile globally adopted a femtocell strategy, the Wi-Fi routers could be replaced with femtocells without messing with the core network, or the two platforms could coexist linked to same core infrastructure.

Of course, neither T-Mobile USA nor its corporate parent have committed to such a scenario, but T-Mobile Ventures’ decision to pursue UMA does give the US branch a bit of breathing room. Several major operators such as Verizon Wireless have said they plan to hold off on their FMC plans while waiting to see which solution gains the most momentum. Dual-mode has several commercial deployments and its development and standardization work are completed, but it has the disadvantage of requiring specialty Wi-Fi enabled handsets. While numerous Wi-Fi handsets have hit the market in the last year, they are still only a fraction of the overall GSM phone market. On the other hand, Wi-Fi home routers are relatively cheap, while femtocell makers have yet to prove they can bring the cost of a home base station down far enough to support mass deployments.

Ubiquisys along with UMA has been gaining more attention in the last year. NEC, Motorola, Netgear and UMA developer Kineto have all joined the UMA femtocell camp, and Ubiquisys has attracted several partners and investors in recent months, including Nokia Siemens Networks and Google.