Sprint Corp. (NYSE: S) is shutting down its iDEN network as part of its Network Vision and move to Long Term Evolution (LTE), but it's also taking some of Clearwire LLC (Nasdaq: CLWR)'s WiMax sites down in the process.

Sprint has already decommissioned 9,600 iDEN cell sites this year, ahead of its planned third-quarter completion date. For Clearwire, whose WiMax equipment is collocated with Sprint iDEN sites in some locations, that means it's being shut down as well. Clearwire notes in a Securities and Exchange Commission (SEC) filing that it isn't likely it'll continue operating its equipment at those sites once Sprint decommissions them. (See Sprint's iDEN Will Be iDONE in June 2013.)

"We determined the useful lives of the Network and base station equipment at these sites should be accelerated beginning in the first quarter of 2012 from a weighted-average remaining useful life of approximately 5 years to approximately 1 - 2 years based on the expected date of decommissioning," the filing reads. "We will continue to monitor the estimated useful lives of our network assets as our plans continue to evolve."

Why this matters
Clearwire has wholesale customers offering service on its WiMax network that were likely counting on another couple of years left in the network -- or at least to be supported until Clearwire's own Long Term Evolution Time Division Duplex (LTE TDD) network is up and running mid-next year. The shortened life expectancy could pose a problem in some markets.

The filing didn't include how many Clearwire cell sites are affected, but a spokesman tells Fierce Wireless that it's only a small number of them. The wholesaler currently offers WiMax in 71 markets, reaching 134 million people.

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— Sarah Reedy, Senior Reporter, Light Reading Mobile