Sprint is Clearwire's largest customer by far, reselling capacity on its network to subscribers who buy 4G devices such as its Evo and Epic smartphones. Under a announced on April 19, Sprint is set to pay Clearwire about $1 billion for WiMax service through the end of 2012.

But relations between the two companies have not always been warm. They spent months working out the April reimbursement deal, and Sprint has relinquished its majority vote on Clearwire's board out of concern over possible liability if Clearwire were to default on loans.

The IDG News Service