A communication system comprising: remote units (26a, ...26i) adapted to exchange radio frequency signals with mobile devices , whereby, at least some of the radio frequency signals comprise information destined for, or originating from, a mobile device; a reference timing source synchronized with a coordinated universal time or a Global Positioning System; a controller comprising one or more modems and connected to an external network , whereby at least one of the modems being a baseband modem and being configured to receive from the external network, process and send first data corresponding to the information to one or more remote units, wherein the controller is separated from the remote units by an intermediate network over which second data corresponding to the information is transmitted in frames between the controller and the remote units, and wherein the second data comprises baseband data; a controller clock synchronized with the reference timing source, whereby the controller clock is adapted to provide timing information to the controller; the communication system characterized in that the system further comprises: a remote unit clock which is synchronized with the controller clock, the remote unit clock is adapted to provide timing information to one of the remote unit, the controller and the remote unit being configured to exchange time stamp messages in order to synchronize the controller clock and the remote unit clock over the intermediate network, wherein at least two of the remote units share a same cell, and timing phases of their transmissions to a particular mobile device are synchronized, wherein the controller and the remote unit are configured to transmit the time stamp messages over the intermediate network in such a way that contention is avoided between time stamp transmissions and baseband data transmissions or between time stamp transmissions of different remote units to the controller. remote units (26a, ...26i) adapted to exchange radio frequency signals with mobile devices , whereby, at least some of the radio frequency signals comprise information destined for, or originating from, a mobile device; a reference timing source synchronized with a coordinated universal time or a Global Positioning System; a controller comprising one or more modems and connected to an external network , whereby at least one of the modems being a baseband modem and being configured to receive from the external network, process and send first data corresponding to the information to one or more remote units, wherein the controller is separated from the remote units by an intermediate network over which second data corresponding to the information is transmitted in frames between the controller and the remote units, and wherein the second data comprises baseband data; a controller clock synchronized with the reference timing source, whereby the controller clock is adapted to provide timing information to the controller; the communication system characterized in that the system further comprises: a remote unit clock which is synchronized with the controller clock, the remote unit clock is adapted to provide timing information to one of the remote unit, the controller and the remote unit being configured to exchange time stamp messages in order to synchronize the controller clock and the remote unit clock over the intermediate network, wherein at least two of the remote units share a same cell, and timing phases of their transmissions to a particular mobile device are synchronized, wherein the controller and the remote unit are configured to transmit the time stamp messages over the intermediate network in such a way that contention is avoided between time stamp transmissions and baseband data transmissions or between time stamp transmissions of different remote units to the controller. <EOS>