Sprint Corp. (NYSE: S)'s plans to partner with LightSquared for Long Term Evolution (LTE) don't exclude WiMax provider Clearwire LLC (Nasdaq: CLWR), but where the wholesaler fits into the new threesome over the long run isn't exactly clear. (See Sprint's $13.5B Jump to LTE With LightSquared.)

The uncertainty sent Clearwire's shares down 20 percent Thursday morning after the deal was announced.

That's because the LightSquared partnership could signal a shift away from Clearwire and WiMax, although the 4G technology is clearly still an important part of Sprint's strategy. It sold 1.7 million WiMax handsets in the second quarter, the first time the carrier has broken out any 4G numbers. Sprint doesn't report WiMax subscriber adds, but Clearwire, which it owns 54 percent of, reported 4.86 million total wholesale subs in the first quarter. (See Sprint Confirms LightSquared Deal, Losses Grow and Sprint Gives Clearwire $1B Boost.)

Sprint CEO Dan Hesse would only reiterate Sprint's commitment to Clearwire, guaranteed through 2012, refusing to explain how it would evolve given the carrier's LTE plans. He's said in the past that a network-sharing agreement with the wholesaler, which owns valuable spectrum in the 2.5 GHz bands and has plenty of frequency available for LTE, could also be in the cards. (See What Will Sprint Reveal of its 4G Plans? and Network Polygamy Ahead for Sprint?)

As part of Sprint's multi-modal "Network Vision" base station plan, it would be technically possible for it to support spectrum from Clearwire, LightSquared and others still. And, with LightSquared's interference issues slowing its progress, Sprint may be forced to look elsewhere.

Hesse made the announcement one day after the Federal Aviation Administration (FAA) released its findings on the GPS interference that could result from LightSquared's original network plans. The wholesaler has already agreed to move down from the upper L-band spectrum, but the FAA refused to concede that the lower L-band wouldn't interfere with airfield operations. (See LightSquared Claims It Has Answer to GPS Problem.)

Sanford C. Bernstein & Co. Inc. Senior Analyst Craig Moffett took the FAA study, along with congressional pressure, to mean there's little chance the Federal Communications Commission (FCC) would approve LightSquared's plan "without another significant course of interference testing, presumably followed by yet another round of remediation proposals and replies."

Given the potential delay, Moffett isn't placing much confidence in LightSquared's partnership with Sprint -- meaning that Sprint's 4G future could still be in the hands of Clearwire, a fact it may be trying to leverage with LightSquared.

"We believe Clearwire is Sprint's, and Sprint's alone, to fund," Moffett wrote in a research note. "And that further underscores our view that Sprint must be valued through the unflattering lens of proportionate (or worse, even full) consolidation with its Clearwire subsidiary."

— Sarah Reedy, Senior Reporter, Light Reading Mobile