Nokia provides telecom equipment and services that are used to build wireless and fixed-line networks. It operates in four segments. The mobile networks segment sells equipment and services to telecom carriers to power public wireless networks. Network infrastructure focuses on fixed-line networks, including switching and routing equipment, optical components, and devices used in fiber-to-the-premises networks. The cloud and network services segment develops software used to operate the core of carrier wireless networks and build private networks for enterprises. Nokia also has a sizable research and patent business, where it licenses technology used by handset providers, consumer electronics firms, and other firms making electronic and Internet of Things products.