Crown Castle International Corp is incorporated in the State of Delaware. It owns, operates and leases towers, rooftop installations and other communication structures (collectively, 'towers) for wireless communications. Effective Ja...nuary 1, 2014, the Company commenced its operations as a REIT. The Company’s main business is the renting of antenna space to wireless communications companies under long-term contracts. The Company also provides certain network services to its customers, including initial antenna installation and augmentation, network design and site selection, site acquisition, site development, site management and other services. The Company conducts its operations through tower portfolios in the United States, including Puerto Rico and Canada 'CCUSA' and Australia 'CCAL'. All of the ...Company's operations are located in the U.S. and Australia. Crown Castle conducts its operations mainly through subsidiaries of Crown Castle Operating Company including certain subsidiaries which operate its tower portfolios in the U.S. and a 77.6% owned subsidiary that operates its Australia tower portfolio. CCUSA - The core business of CCUSA is the renting of antenna space on its towers. The Company leases access to its distributed antenna systems. It predominately rents to wireless carriers under long-term contracts for the transmission of a variety of wireless signals related to wireless voice and data transmission. The Company also offers its customers certain network services relating to its towers. Crown Castle works with large national wireless carriers, and in general, its customers are mainly comprised of providers of wireless voice and data services who operate national or regional networks. CCUSA competes with other independent tower owners, which also provide site rental and network services, wireless carriers, which build, own and operate their own tower networks and lease space to other wireless communication companies, and owners of alternative facilities, including rooftops, water towers, broadcast towers, distributed antenna systems, and utility poles. Some of the larger independent tower companies with which CCUSA competes in the U.S. include American Tower Corporation, SBA Communications Corporation, Global Tower Partners and TowerCo. CCAL - Crown Castle's main business in Australia is the renting of antenna space on towers to its customers. In Australia, CCAL competes with wireless carriers, which own and operate their own tower networks; service companies that provide site maintenance and property management services; and other site owners, such as broadcasters and building owners. The Company holds, through certain of its subsidiaries, certain licenses for radio transmission facilities granted by the FCC, including licenses for common carrier microwave service, commercial and private mobile radio service, specialized mobile radio and paging service. Both the FCC and the Federal Aviation Administration regulate towers used for wireless communications transmitters and receivers for US Operation.