Clearwire has teamed up with the world’s largest wireless operator, China Mobile, to spur the development of TD-LTE devices.

The development of TD-LTE is less mature than FDD-LTE, the version used by Verizon Wireless and AT&T.

China Mobile’s 621 million wireless subscribers gives it the size and clout needed to spur the TD-LTE ecosystem, and its decision to back TD-LTE may help convince other operators that they can bank on the technology. Both China Mobile and Clearwire intend to deploy TD-LTE on unpaired spectrum in the 2.5 GHz band.

China Mobile Chairman Jianzhou Wang said in a statement that the availability and cost of TD-LTE devices would be “critical success factors.”

“The cooperation with Clearwire will leverage economies of scale in the two largest markets in the world to speed up the development of TD-LTE devices,” he said.

In an interview, Clearwire Chief Technology Officer John Saw said the alliance with China Mobile gives “a lot of credibility about our LTE plans.”

“We’re not alone (with TD-LTE), we’re going to be part of potentially the largest 4G ecosystem in the world,” Saw said.

The companies are partnering on multi-mode, multi-band devices with minimum component complexity and cost. TD-LTE devices are currently available and have been used by both China Mobile and Clearwire in commercial trials of the technology, but have not yet reached the point to generate significant economies of scale.

China Mobile and Clearwire aim to generate high volume TD-LTE chipsets and devices that should be commercially available starting next year. They are also working on global roaming between TD-LTE, FDD-LTE and legacy 2G and 3G networks.

Clearwire has been isolated by its WiMAX strategy, which quickly fell out of favor as other operators decided to deploy LTE. Its plan to overlay portions of its WiMAX service with TD-LTE will help bring its network technology back into the mainstream.

However, Clearwire lacks the $600 million it needs to construct the network. Saw said Clearwire is doing what it can to prepare for the project as it works to find funding. Earlier this year, Clearwire cofounded the Global TD-LTE Initiative with China Mobile, Vodafone, SoftBank and Bharti Airtel. The group is working on standards and requirements for TD-LTE networks, as well as devices.

Clearwire wants to lease capacity on its TD-LTE network to FDD-LTE operators such as MetroPCS, whose spectrum shortage has impeded the speeds of its mobile broadband network.

For Clearwire’s plan to work, devices must have chips that incorporate both flavors of the technology. Saw dismissed the possibility that this requirement could be a barrier to Clearwire’s plan, saying he expects that “all chipsets will support both formats. There will be strong demand for both.”

Major semiconductor companies including Qualcomm have made chips that run both TD-LTE and FDD-LTE.