DDB takes the business over from the Florida-based agency St John & Partners. The Los Angeles office of M&C Saatchi and the Richards Group in Dallas also contested the business.
Clearwire, which launched four years ago, has raised more than $1 billion from investors that include Intel and Motorola. A forthcoming IPO is expected to raise an extra $400 million. The company's wi-fi system offers a high-speed internet service over large areas, as well as cheap phone connections.