The head of T-Mobile USA has announced his resignation from the company, stepping down after 15 years with the carrier. Robert Dotson, president and chief executive officer, will leave within 12 months, sticking around in some capacity until May 2011 to ensure a smooth transition for his successor.

His designated replacement is Philipp Humm, former CEO of T-Mobile’s domestic operation in Germany and current chief regional officer for Europe. Humm will officially take over as CEO of T-Mobile USA in February 2011.

“It has long been my intent to step away from the business at this stage in my life in order to devote more time to family and to take on entirely new and unique challenges. That change can only be made possible if a suitable successor is in place,” said Dotson.

T-Mobile USA has long been the powerhouse of Deutsche Telekom’s mobile operations, sitting just behind Germany in terms of revenue generation. The US arm brought in net revenues of €3.88bn for the first quarter of 2010, down 7.8 per cent year on year, while the German operation brought in €5.8bn for the same period.