Among other things, a communication system comprising remote units and a controller is described. The remote units exchange radio frequency (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 controller is separated from the remote units by an intermediate network over which second data corresponding to the information is carried in frames between the controller and the remote units. The second data comprises baseband data and at least some of the baseband data is compressed in a frequency domain. The remote units and the controller are configured to compress the baseband data for transmission over the intermediate network.