Among other things, a communication system comprising remote units and a controller is described. Each of the remote units comprises one or more radio frequency (RF) units to exchange RF signals with mobile devices. At least some of the RF signals comprise information destined for, or originating from, a mobile device. The controller comprises one or more modems and is connected to an external network. At least one of the modems is a baseband modem and is configured to pass first data corresponding to the information. The at least one of the modems is configured to perform real-time scheduling of the first data corresponding to the information. The controller is separated from the remote units by an intermediate network. The intermediate network comprises a switched Ethernet network over which second data corresponding to the information is carried in frames between the controller and the remote units.