A wireless communication system comprising: a plurality of base stations; a plurality of remotely located terminal units; the base stations and the remotely located terminal units comprising respective communication modules configured for transmitting and receiving data over operational wireless communication links between at least the base stations and the terminal units, the communication modules including respective in-channel receiver elements for signals received over the operational communication links; and at least one base station controller configured to control channel parameters used by the base stations for the respective communication links, the channel parameters including allocations of frequencies for use in the communication links; characterised in that: the system includes respective in-channel detectors and out-of-channel detectors configured for detecting extraneous received signals; the in-channel detectors are configured to analyse signals from the communication modules in the base stations received over operational communication links, and the out-of-channel detectors include respective out-of-channel receiver elements and are configured to monitor possibly available channels alternative to the operational communication links for a duration of channel availability check procedures for detecting radar signals as the extraneous received signals; the base station controller is configured to receive reports of detection of extraneous received signals from the in-channel detectors and out-of-channel detectors, to register whether channels are available or not for communication links, and to allocate to the base stations respective target channel frequencies available for operational and alternative communication links; the system is configured to store the respective allocated target channel frequencies that have been checked successfully to be available for operational and alternative communication links; and the base stations are configured to change channel parameters used for the respective operational communication links to the allocated stored target channel frequencies that have been checked successfully to be available for alternative communication links without further availability checking of the alternative communication links. a plurality of base stations; a plurality of remotely located terminal units; the base stations and the remotely located terminal units comprising respective communication modules configured for transmitting and receiving data over operational wireless communication links between at least the base stations and the terminal units, the communication modules including respective in-channel receiver elements for signals received over the operational communication links; and at least one base station controller configured to control channel parameters used by the base stations for the respective communication links, the channel parameters including allocations of frequencies for use in the communication links; the system includes respective in-channel detectors and out-of-channel detectors configured for detecting extraneous received signals; the in-channel detectors are configured to analyse signals from the communication modules in the base stations received over operational communication links, and the out-of-channel detectors include respective out-of-channel receiver elements and are configured to monitor possibly available channels alternative to the operational communication links for a duration of channel availability check procedures for detecting radar signals as the extraneous received signals; the base station controller is configured to receive reports of detection of extraneous received signals from the in-channel detectors and out-of-channel detectors, to register whether channels are available or not for communication links, and to allocate to the base stations respective target channel frequencies available for operational and alternative communication links; the system is configured to store the respective allocated target channel frequencies that have been checked successfully to be available for operational and alternative communication links; and