Radio spectrum is a finite national resource governed by regulatory authorities such as the FCC in the United States, Ofcom in the United Kingdom, BNetzA in Germany, and TRAI in India. These regulators allocate spectrum to mobile operators primarily through competitive auctions using formats like simultaneous multi-round ascending, combinatorial clock auction, or sealed-bid processes. Auction outcomes determine which operators can deploy 5G on which frequencies in which geographic regions, making spectrum acquisition a strategic corporate decision that shapes network architecture and competitive positioning for the next 15 to 20 years.