Sprint (S) on Wednesday added to its already-robust spectrum portfolio by acquiring 20MHz of PCS spectrum from U.S. Cellular. Under the carriers’ agreement, Sprint will pay U.S. Cellular $480 million to acquire both the spectrum and “customers in parts of Illinois, Indiana, Michigan, Missouri and Ohio including the Chicago and St. Louis markets” totaling approximately 585,000 subscribers. All four major carriers in the United States have been scrambling over the past year to acquire more spectrum to use in their LTE networks, and Verizon (VZ), AT&T (T) and T-Mobile have also acquired more spectrum licenses from a wide variety of sources, including cable companies and satellite radio.