Having announced earlier that it intends to launch LTE service next year, T-Mobile USA is now going into a little more detail on how it plans to make that happen. In a press release talking about its "challenger strategy," the company says that it'll invest some $4 billion into network upgrades — $1.4 billion of which will happen in the next two years — to achieve LTE service in the "vast majority" of the top 50 markets by 2014, with a faster 20MHz-thick slice of LTE operational in three-quarters of the top 25 markets.

It's long been known that T-Mobile is starved the amount of spectrum required for a proper nationwide LTE deployment, though, and the carrier reiterates that here: not only is this plan contingent on regulatory approval of the spectrum it won from AT&T after the takeover failed, but it says that it still needs "additional AWS spectrum for broader / deeper LTE build-out," and it's unclear whether the company has spectrum purchases budgeted into the $4 billion figure. In the meantime, it'll be relying largely on refarming of existing 3G bands to kick off service.