Clearwire has said that build-out of its new TD-LTE network is now underway and will pick up significantly in the fourth quarter. The new network marks a transition away from WiMAX, though Clearwire says it is working closely with its current wholesale partners – notably Sprint – during the switch.

Clearwire plans to deploy 5,000 network sites in 31 cities by the end of H1 2013, targeting major urban centres such as New York, San Francisco, Los Angeles, Chicago and Seattle. "We're focused on putting in capacity where congestion will happen quickly," CFO Hope Cochran told an investor conference this week, reports Fierce Wireless.

This strategy is linked to the Sprint deal, with the US number-three operator expected to to use Clearwire's TD-LTE network in conjunction with its own FDD-LTE service. Cochran said that Clearwire is "talking to Sprint at all times to make sure it's there when they need it."

The Sprint wholesale deal is thought to account for the vast majority of Clearwire’s 11 million connections.

Cochran added that Clearwire intends to make use of vendor financing for its LTE network build out, and will announce its vendors next month.

In a separate development, Clearwire lost one of its earliest backers this week as Time Warner Cable (TWC) announced it is to sell its entire 7.8 percent stake in the network.

TWC invested US$550 million into Clearwire in 2008, though its shares are now thought to be worth less than US$75 million. The firm stopped reselling Clearwire's WiMAX services earlier this year.