A system is disclosed in which a base station defines a search space, in which a communication device can search for control information. The search space is characterised by at least first information which is related to a starting subframes of a plurality of portions of the search space and second information which is related to a periodicity between respective starting subframes, each portion representing a different candidate for the transmission of control information. The base station obtains a parameter indicating both the initial starting subframe and the periodicity and transmits the generated parameter to the communication device.