Spectrum licenses are the lifeblood of the wireless industry. In 2008, the FCC auctioned off brand new licenses in the 700 MHz band, after kicking UHF TV stations off that band.

AT&T (NYSE:T) and Verizon (NYSE:VZ) walked off with the lion's share of winning bids while the FCC pocketed a cool $19.6 billion. The two telecom giants are still riding high on the competitive advantage provided by this big spectrum investment.

The next time, T-Mobile (NASDAQ:TMUS) and Sprint (NYSE:S) will fight for some table scraps in order to stay competitive. Or maybe they'll team up and go head-to-head with the two big guys as a third 100-million-subscriber giant.

Either way, there will be about 120 MHz of former TV spectrum licenses available when the FCC pulls the trigger, probably in 2015. Carriers might spend as much as $46 billion on these licenses. The outcome of this auction will reshape the American wireless industry for years to come -- maybe even decades.

So why do the carriers fight for their lives over certain scraps of wireless transmission rights? The infographic below lays out the basic facts.