There is described a method of operating a multi-mode communication unit. For each radio frame of a radio communication frame structure, the unit selectively sets a mode of radio frequency operation for one of transmission and reception for a selected radio frame duration, for operation in a radio communication mode of operation or in a sensing mode of operation. The unit may also interrupt a transmission task within a given radio frame at a time selected in accordance with a sensing instant of a second communication unit to which the data being transmitted and perform a different task for a duration of the sensing instant of the second communication unit.