After a successful campaign in the fall which raised $4 billion, Sprint is looking to sell another $2B in company bonds via a private sale. This money will be going towards network expansion and upgrade (LTE), as well as to possibly help fund Clearwire. This is all part of Sprint's Network Vision plan, which will ultimately see their iDEN network shut down and their CDMA offering on both the 800 and 1900MHz frequencies.
Sprint owns about half of Clearwire, which is having some financial difficulties as it looks to transition from WiMax to LTE. The company looks to have 5,000 TD-LTE cell sites functional by mid 2013. This type of LTE is different than what AT&T and Verizon employ, but Clearwire claims that it is more advanced and will be more adopted world-wide.