Clearwire announced McCaw's departure in a on Thursday. His departure was not caused by any disagreement with the company over its operations, policies or practices, Clearwire said in the filing.

McCaw, a cellular industry pioneer, founded Clearwire as a pre-WiMax wireless broadband operator. The company merged with part of Sprint Nextel in 2008 to form the current Clearwire. When the new entity was formed, investor Eagle River Holdings named McCaw as its chairman as part of a deal involving partners including Sprint, Comcast, Time Warner Cable and Google. Eagle River has the right to nominate a board member to replace McCaw and has indicated to Clearwire that it intends to name former CEO Benjamin Wolff in his place, according to the filing.

The carrier is constructing a WiMax mobile broadband network across the U.S. but has faced challenges in funding the massive buildout. As of Friday, the end of the year, Clearwire's network reached just over 110 million U.S. residents, falling short of the goal of 120 million that the company stated in early 2009.

In November, Clearwire , reduce its contract workforce and cut back some marketing and development activities in an effort to conserve cash. In early December, it raised US$1.4 billion through debt offerings.

On Tuesday, Clearwire finally launched its service commercially in the San Francisco Bay Area, as it had promised to by year's end. But after beginning 2010 as the only major provider of the fast mobile broadband services typically called 4G, by the end of the year Clearwire faced competition from fast networks operated by Verizon Wireless, T-Mobile USA and MetroPCS. When , the carrier said it could reach 110 million people.