"We're making very good progress, we believe, on the technical front with Clearwire," Hesse said.

Sprint hopes to better manage its fixed network costs by offloading data traffic to Clearwire's network, which has significant capacity for growth because Clearwire holds an average of more than 100MHz of spectrum in markets across the U.S. Larger bands of spectrum allow for greater speed or capacity on a network.

Sprint plans to launch its LTE network in the middle of next year and run it partly on spectrum repurposed from its 3G data network. LTE will be part of Sprint's Network Vision infrastructure, a flexible network designed to accommodate multiple mobile technologies and frequencies. The company a $9 billion deal with hybrid satellite-LTE startup LightSquared that would give Sprint access to additional LTE capacity.

Sprint still plans to carry out the LightSquared deal if the FCC allows that company to build its network, Hesse said. Sprint has estimated the LightSquared deal would allow it to meet capacity needs for an additional year without having to build more capacity of its own. Working with Clearwire could give it multiple years beyond that, Hesse said.

Clearwire was formed in 2008 as a joint venture among Sprint, Google and several cable operators, including Comcast and Time Warner Cable. It built out the first national 4G network in the U.S. using WiMax, which predated LTE but has now taken a backseat to the newer technology in terms of global adoption by mobile operators.