A wireless communication system comprising: a base station (104A to 104M); and a plurality of remotely located terminal units (106A to 106N); the base station and the remotely located terminal units comprising respective communication modules (302 to 310) for transmitting and receiving data over operational wireless communication links between the base station (104A to 104M) and the terminal units (106A to 106N), the communication links being assigned to respective sub-channels comprising tiles separated by frequency and time; wherein the base station (104A to 104M) and/or at least one terminal unit (106A to 106N) includes at least one detector (108, 318, 320) for analysing signals from the communication modules for detecting extraneous received signals; characterised in that: the at least one detector (108, 318, 320) is configured for analysing signals from the communication modules (302 to 310) in unassigned tiles of the communication links; the at least one detector (108, 318, 320) is configured for discriminating between a first type of extraneous signals detected in an unassigned tile or group of unassigned tiles of one sub-frame and also detected in other unassigned tiles or groups of unassigned tiles, and a second type of extraneous signals detected in the unassigned tile or group of unassigned tiles of one sub-frame but not detected in other unassigned tiles or groups of unassigned tiles; and the reaction of the base station (104A to 104M) to detection of the first type of extraneous signals is configured to be different from the reaction of the base station to detection of the second type of extraneous signals. a base station (104A to 104M); and a plurality of remotely located terminal units (106A to 106N); the base station and the remotely located terminal units comprising respective communication modules (302 to 310) for transmitting and receiving data over operational wireless communication links between the base station (104A to 104M) and the terminal units (106A to 106N), the communication links being assigned to respective sub-channels comprising tiles separated by frequency and time; wherein the base station (104A to 104M) and/or at least one terminal unit (106A to 106N) includes at least one detector (108, 318, 320) for analysing signals from the communication modules for detecting extraneous received signals; the at least one detector (108, 318, 320) is configured for analysing signals from the communication modules (302 to 310) in unassigned tiles of the communication links; the at least one detector (108, 318, 320) is configured for discriminating between a first type of extraneous signals detected in an unassigned tile or group of unassigned tiles of one sub-frame and also detected in other unassigned tiles or groups of unassigned tiles, and a second type of extraneous signals detected in the unassigned tile or group of unassigned tiles of one sub-frame but not detected in other unassigned tiles or groups of unassigned tiles; and the reaction of the base station (104A to 104M) to detection of the first type of extraneous signals is configured to be different from the reaction of the base station to detection of the second type of extraneous signals.