T-Mobile USA officially launched its Unlicensed Mobile Access (UMA) service nationwide on Wednesday, becoming the first US carrier to allow calling over both wifi and cellular networks.

Today’s announcement follows a soft launch of the service in the Western Washington/Seattle area in October.

The HotSpot @Home offering means that customers can place free calls over a wifi network while at home – or at the 8,500 T-Mobile HotSpot locations across the country – and use the cellular network when out of range of wifi, resulting in a cheaper phone bill.

T-Mobile has made two HotSpot phones available – the Samsung t409 and the Nokia 6086. Each phone retails for $49.99 with a two year contract on a qualifying rate plan at $9.99 per month for a single line, and $19.99 per month for up to five lines on a FamilyTime plan. The package includes a wireless router from D-Link or Linksys.

Being UMA-based, the handsets will allow calls to be seamlessly transferred between T-Mobile’s GSM/GPRS/EDGE wireless network and wifi.

“More people than ever are looking to drop their home landline phone and pocket the savings. However, they don’t want to use all their wireless minutes talking from home. Our new service solves this dilemma once and for all,” said Robert Dotson, president and CEO of T-Mobile USA.

Telecoms.com believes T-Mobile is rolling out UMA in a bid to maintain a competitive edge while it rolls out 3G.

Work on its 3G network has already begun, with a majority of the rollout to be completed before 2008. But in the meantime T-Mobile plans to fill its speed gap by sending calls over other carriers’ broadband networks.

Most interest in UMA technology has come from carriers with both fixed and mobile networks with a view to Fixed Mobile Convergence (FMC) strategies.

But with the exception of a handful of countries in Eastern Europe, T-Mobile’s parent, Deutsche Telekom, has no fixed networks outside Germany. However, Dotson recently said that UMA was important to the operator because more than 10 per cent of T-Mobile USA users do not have a traditional home phone.

By giving T-Mobile USA subscribers wifi hubs to install at home, T-Mobile could try to hitch a lift on DSL and cable broadband deployment in the US as calls made over a competitor’s fixed line network would generate Call Detail Records (CDRs) on T-Mobile’s own network.

One analyst recently told telecoms.com: “T-Mobile USA has got very little to do with the rest of the company franchises. In fact, it tends to be as independent as possible. Because it perceives the German and international business as a barrier…it doesn’t see it as a help in terms of brand leverage.”

That independence seems to be working. The US division recorded the highest organic customer growth of all the national companies. With a 15.4 per cent increase in 2006, it passed the 25 million subs mark. It also led the way in terms of revenue growth in 2006 with a 14.6 per cent increase on the previous year. It raised Eur13.6bn in revenues, which translates to an EBITDA of Eur3.7bn for the period.