A distributed antenna system with a plurality of remote radio units is disclosed. The distributed antenna system includes a jammer signal generator for generating a jammer signal in at least one frequency range to be blocked on detection of an uplink signal in a coverage area, as well as at least one antenna element for transmitting the generated jammer signal in the coverage area. The jammer signal will ensure that any mobile devices or stations within the coverage area are unable to transmit radio signals as the frequency range(s) on which the radio signals should be transmitted are blocked by the jammer signal.