According to the Wall Street Journal:

…The company is gearing up to make a serious run at buying wireless spectrum, a chunk of the airwaves that can be used to provide mobile phone and Internet services, in a Federal Communications Commission auction in January. Google is prepared to bid on its own without any partners, say people familiar with the matter. It is working out a plan to finance its bid, which could run $4.6 billion or higher, that would rely on its own cash and possibly some borrowed money.

Google, meanwhile, already is running a test version of an advanced wireless network at its Mountain View, Calif., headquarters, gaining operating experience that could come in handy if it wins the spectrum and decides to run a full-scale national mobile carrier, according to people familiar with the matter. …

Google Has Even Bigger Plans for Mobile Phones - WSJ.com