The FCC approved multiple measures today that will in the end see AT&T receiving a diverse grouping of spectrum from several different companies. The different bits of spectrum all fall into the WCS (Wireless Communications Service) and AWS-1 (Advanced Wireless Services) bands, which cover the 2305-2320 / 2345-2360MHz and 1710-1755 / 2110-2155MHz frequency ranges, respectively. The spectrum is being purchased from four different companies -- Nextwave, Horizon, Comcast, and SG&E.
There's a pretty complicated set of small parcels of spectrum being transferred in several different markets, which can be seen at the FCC source link below if you're so inclined. If you don't feel like digging through those (we don't blame you,) the end result is AT&T gaining spectrum in 608 different market areas that cover a total of 82-percent of the U.S. population. AT&T of course plans to use this spectrum to improve its LTE situation in these new markets.