With the announcement, made alongside its second-quarter financial report on Wednesday, the carrier is finally lining up with the majority of the world's mobile operators that have made LTE (Long-Term Evolution) a de facto standard for 4G infrastructure. But because of its large holding of radio spectrum, Clearwire said it will be able to keep its WiMax network and keep offering services on it indefinitely.

The company plans to deploy LTE first in densely populated areas of its existing WiMax footprint where demand for mobile data is highest. Based on its own tests, Clearwire believes it can deliver between 50M bps (bits per second) and 60M bps to users, on average. The gear it plans to roll out would also support the faster LTE Advanced in the future. But even if it can raise the necessary funding, Clearwire doesn't expect to be able to start its rollout for about six months and thinks it would take about a year to carry out.

Clearwire has long been expected to use LTE, especially following extensive tests it has conducted on the technology. Its existing infrastructure is compatible with the new technology to the point that in many markets Clearwire said it will be able to deploy LTE just by adding line cards to its base stations. But before it can move on the plan, the loss-making and relatively cash-strapped carrier will need to raise $600 million for capital expenditures, by its own calculation.

Though Clearwire was first to market with a 4G network in 2008 and now has more than 7 million subscribers, it has had to cut back on marketing and other functions in the face of an expensive network buildout. The WiMax infrastructure reaches about 132 million U.S. residents now, but its expansion has been relatively small this year. The company faces competition from Verizon Wireless' LTE network and a looming LTE buildout by AT&T.

Its majority owner and biggest wholesale customer, Sprint Nextel, announced a deal of its own last week with startup LightSquared under which Sprint will build an LTE network that it can share with the cellular upstart. However, there's nothing in the current wholesale deal between Sprint and Clearwire to keep Sprint from reselling capacity on the planned LTE network, Clearwire officials said.